ferocia animi

Introduction to Artificial Intelligence

2011-12-27T16:38:00.000-08:00

Introduction to AI

Some time ago I have joined to Introduction to Artificial Intelligence it is online course that is based on Stanford CS221, Introduction to Artificial Intelligence.

This class introduced students to the basics of Artificial Intelligence, which included machine learning, probabilistic reasoning, robotics, and natural language processing.

My reason to join this class was simple I wanted to know more. I took 82% it isn't so bad for not native speaker.

If you want to get more you can join a lot of next online courses- http://www.class-central.com/

Trouble with resources in WP7

2011-08-16T06:49:00.000-07:00

I started a few projects on WP7. It was done just for fun and for improving my skills (Fun was profitable - I won in Ukrainian WP7 competition). So I had completed my projects and tried to localize it.

I met some issues:

If you have experience in developing for web silverlight - first isn't new for you. When I edit/add/remove a item in resources's file I need to open resources designer's file and change access modifiers of parameterless constructor from "internal" to "public".
It is know issue and know fix - proof.
Second was new for me. It is strange issue because it appeared only in one of my projects. I created resources file and added key in Resources section of app.xaml (for binding to resources in my xaml files). My project started to crash after this.
I had spent some time and found source of the issue. I noticed that Resource class (auto generated) is internal. I checked "Custom tool" field in properties of resource file. It was filled "ResXFileCodeGenerator" value. In my other projects this field contained "PublicResXFileCodeGenerator" value. I didn't found detailed description of "ResXFileCodeGenerator" but looks like that it is obsolete tool. I no idea how to it was set in my project.

One more note: it is for WP7 without "Mango" update. I hope I will not meet such issues after this update.

Trimmed TextBlock for Windows Phone 7.

2011-02-07T06:05:00.000-08:00

Unfortunately WP7 is based on Silverlight 3. So we can't use some nice features of Silverlight 4 i.e. dynamic key word or TextBlock's trimming. But I've solved issue with trimming for Silverlight 3. Solution is here. Let me explain which code I use in WP7 project:

Generic.xaml: File contains style and template for custom control. This file is located in Themes folder. WP7 tools doesn't contains Resources.xaml file template. So I created xml file and name it as "Generic.xaml".
TrimmedTextBlock.cs: It is implementation of custom control. I just copied this file. One more note: I decrement c_POINTS_COUNT to "1" because screen resolution of desktop and mobile versions are different.

Easy coding.

"using" directive in aspx's pages.

2010-12-15T11:29:00.000-08:00

It is funny but I don't know about this. I used full name of type (namespace+type name) in aspx pages. It is unnecessary. ASP.NET has directive for this.
<%@ Import namespace="value" %>
Sometime we omit in haste important things.

UPD: And more easy for Razor view engine:
@using MyNamespace

ASP.NET MVC aplication inside in an iframe (fix issue with empty session).

2010-11-15T13:48:00.000-08:00

I developed application using ASP.NET MVC framework. It worked well but when I put my app inside of iframe I founded that in some case in Internet Explorer application missed session.
I started to investigate for the source of the issue.
I founded that application worked well if I decrease security level in the IE. But this fix weren’t suitable for me (I can`t request something in the customers). So I carried on with investigation.
Well description what happen I founded on the follow page (unfortunately, I didn’t found English version of this page, so I used google translate for figure out this article).
So for fix this I should add “PSP” header to response. How can I do it for the ASP.NET MVC application? In classic ASP.NET it is easy to do in code behind or in aspx file. I overrode ExecuteResult method in all classes inherited from ActionResult that used in my application. ViewResult for example:

public class CustomViewResult : ViewResult
 {
     public override void ExecuteResult(ControllerContext context)
     {
         context.HttpContext.Response.AddHeader("P3P", "CP=\"CAO PSA OUR\"");
         base.ExecuteResult(context);
     }
 }

After it I used my customized classes in base controller of all controllers in application (It was very nice idea to implement one base controller for all other controllers, wasn't it?). For example:

public class BaseController : Controller
 {
     protected override ViewResult View(string viewName, string masterName, object model)
     {
         if (model != null)
         {
             base.ViewData.Model = model;
         }

         return new CustomViewResult
         {
             ViewName = viewName,
             MasterName = masterName,
             ViewData = base.ViewData,
             TempData = base.TempData
         };
     }
 }

For figure out which methods I need to override I used cool tools - .NET Reflector.

Unit Tests for ASP.NET MVC application that uses resources in code behind.

2010-09-16T12:19:00.000-07:00

Download source files - here.

Some time ago I start to play with ASP.NET MVC. It is very well pattern and Microsoft made nice choose that implemented it for ASP.NET in my opinion.

I started a project that uses ASP.NET MVC. This project requests multilingual support. I use resources for this. It works well when I use resource's properties in the View's layer but when I call resource's properties from code behind. It's something likes to next:

public ActionResult Index()
{
ViewData["Message"] = CommonResource.WELCOME;
return View();
}

It works but I pay attention that this code breaks my Unit Tests. My Unit Tests looks like:

[TestMethod]
public void Index_Test()
{
//// Arrange
var controller = new HomeController();

// Act
var result = controller.Index();

// Assert
Assert.IsInstanceOfType(result, typeof(ViewResult));
}

It happens because I run my code in other project and my ResourceManager is not filled (it equals to null). How can I fix it? A first idea that came to mind is "extract interface".. but it is very annoying because resource's class is auto-generate and I should update this code after each updating of resources.. I made some research and found additional way for extracting resources - HttpContext contains GetGlobalResourceObject method! It is well way because I can set mock for HttpContext and for any its methods or properties.

Note: GetGlobalResourceObject returns object but I use only strings for localization. So I create linq method for HttpContext that returns string if it presents:

public static string GetGlobalResource(
   this HttpContextBase httpContext
  , string classKey, string resourceKey)
{
var result = httpContext.GetGlobalResourceObject
                    (classKey, resourceKey);
return null != result
  ? result.ToString() : string.Empty;
}

Pay attention, MissingManifestResourceException is possible in this code if you pass incorrect key/keys!

So I change pieces of code in Controller's classes in the next manner:

public ActionResult Index()
{
ViewData[CommonStrings.MESSAGE] = HttpContext
        .GetGlobalResource(CommonStrings
            .COMMON_RESOURCE, CommonStrings.WELCOME);
return View();
}

After it I should change my Unit Test's methods in next manner:

[TestMethod]
public void Index_Test()
{
//// Arrange
var httpContextMock = MockRepository
              .GenerateMock<HttpContextBase>();
httpContextMock.Stub
   (x => x.GetGlobalResource(
      CommonStrings.COMMON_RESOURCE, CommonStrings.WELCOME))
   .Return(CommonStrings.WELCOME);

var controller = new HomeController();
var context = new ControllerContext
  (httpContextMock, new RouteData(), controller);
controller.ControllerContext = context;

// Act
var result = controller.Index();

// Assert
Assert.IsInstanceOfType(result, typeof(ViewResult));
ViewDataDictionary viewData = ((ViewResult)result).ViewData;
Assert.AreEqual(CommonStrings.WELCOME
        , viewData[CommonStrings.MESSAGE]);
}

Moreover, you can see that I added additional checking related to localization.

Trimmed TextBlock for Silverlight.

2010-03-24T08:01:00.001-07:00

Download source files - here

Not always Silverlight TextBlock that contains long text has enough space for shows all this text. TextBlock clips text in this case - this behaviour isn't best way for this. Because I wait that TextBlock not only trims but also adds "..." to clipped text. WPF has brilliant property that helps to resolve this trouble - TextTrimming. I implemented this possibility for Silverlight and now want to present it for you. Furthermore I implemented ToolTip that shows trimmed text (only if text is trimmed!)

Enjoy!

UPD: I have just updated performance and behaviour when width defined zero.

Trips&Ticks: Easy way to navigate from XAML to class's definition.

2010-02-24T03:07:00.000-08:00

Working with XAML code in VS2008 I have just found that I can easy jump to class's or property definition. If I press CTRL and click left mouse button on certain class or property in XAML I will be immediately switched to Object Browser (if it is class or property of .NET or external dll) or to class's or property definition in my code (if it is class or property from my sources).

Eugene Dolinskyy just pay my attention that "clear" VS2008 doesn't have this possibility. This feature is presented by ReSharper.

Zoom event for FlowDocumentPageViewer (corrected)

2010-01-25T13:33:00.000-08:00

Download source files - here

When I wrote my article Zoom and page chaged events for FlowDocumentPageViewer I make mistake, you can read about it - there. However Martin offer solution for this problem. But I don't like this solution, overriding of OnPropertyChanged isn't best solution because this method is risen in many cases so any logic there is serious performance issue.

So how can we fix it in other way? We can find object of Slider in Visual Tree of FlowDocumentPageViewer and subscribe to ValueChanged event and call OnZoomChanged(); there.

Bingo! It fixes my trouble.

Trips&Ticks: How to implement GroupName for RadioButton in WPF DataGrid's column?

2010-01-24T00:46:00.001-08:00

Download source files - here

It is very easy. We should use DataGridTemplateColumn for this. My acquaintance requested to me show it. I added source code where implemented this.

Some notes:

You should turn off AutoGenerateColumns feature. In other case control will have duplicate values.
I recommend to turn off CanUserAddRows. In other case user can pick undefined row.

Enjoy Yulian ;).

Web access to Team Foundation Server.

2010-01-15T01:11:00.000-08:00

I have been starting to work with Team Foundation Server as source control and bag tracking system for 2 month. In this time we migrated from one TFS to another. So sometime we needed access to both these servers (one as bug track, another as source control). I said to my manager about web access tool for TFS he heard it already that this tool is very cool but expensive.

It isn't truth. This tool is useful but full freeware! Because Microsoft Acquired TeamPlain 3 year ago :). When I tried to find it - I was a bit disappointed I couldn't found this tool - all links were broken. Little find out shows that TeamPlain is renamed to Team System Web Access. I founded article that describes How to: Install Team System Web Access (this page also contains broken link to installation of Team System Web Access :) ) and after all I found download page.
That isn't fresh news, but it is very upset that this useful tool is so hard for found.

Useful code snippets for WPF developer.

2009-11-24T06:51:00.000-08:00

Download snippets - here

I want to share very useful in my opinion code snippets for WPF developers. Most of they were created my friend - Dmitrij Zakharov. Moreover I want to add a short description to each snippets.

Note: The Code Snippet Inserter inserts a code snippet at the cursor location, or inserts a surround-with code snippet around the currently selected code.

Don't you know how to use code snippets? You should read next article - How to: Use Code Snippets (C#). You should copy the code snippets files to Installation directory\Microsoft Visual Studio 9.0\VC#\Snippets\1033\NetFX30 in your PC for start to use.

Let me start:

addowner - Adds owner to the dependency property that already exists.
defstyle - Code snippet for overriding DefaultStyleKey.
propa - Code snippet for an attached property using DependencyProperty as the backing store. It is the common code snippet that is delivered with installation of VS2008
propdp - Code snippet for a property using DependencyProperty as the backing store. It is the common code snippet that is delivered with installation of VS2008
propdpec - Code snippet for a property with value caching and events support using DependencyProperty as the backing store.
propdpr - Code snippet for a property using DependencyPropertyKey as the backing store.
routedcmd - Implements routed command executor.
routedevent - Declares and implements routed event.

PS: Do you want to know more? - read about Default Code Snippets.

Zoom and page changed events for FlowDocumentPageViewer

2009-11-19T15:17:00.000-08:00

Download source files - here

My old known Bala send to me this link.

Kent Boogaart has written an article that describes approach searching and highlighting text in FlowDocumentPageViewer - Search and Highlight Text in an Arbitrary Visual Tree. Unfortunate, two serious issues present there. I copy theirs description from msdn forum:

When I change the pages of the FlowDocumentPageViewer, my Rectangular highlighted area remains the same and it is not sinking with the Text.
When I zoom in or zoom out of the FlowDocumentPageViewer, the text gets zoomed but the Highlight rectangle remains in the same position.

Seems.. solution should be easy - just add DoSeach() method in PageChanged and ZoomChanged event handler methods of FlowDocumentPageViewer but it doesn't have events for notice these actions. So I decided just to implement these events :). FlowDocumentPageViewer doesn't have protected and virtual methods like OnZoomChanged or OnPageChanged. It was bad. But I found four protected and virtual methods that could help me they are OnNextPageCommand(), OnPreviousPageCommand(), OnIncreaseZoomCommand() and OnDecreaseZoomCommand(). When I added call to rise my events in theirs override methods I found that this approach wasn't work. It happened because command logic works through concurrency approach. I called the rise methods through BeginInvoke for delay the calls rise methods - and problem was solved.

You can download sources with fix above.

PS: I didn't have time for full investigate sources.. but one question. Why did Kent use SearchRectangle class? In my opinion common Rect is enough.

How to implement TextBox with PlaceHolder in WPF

2009-11-16T07:10:00.000-08:00

Download source files - here

Using PlaceHolder is very useful thing for UI in any type application. I want to show a short way how can you implement it in WPF.

You can custom TextBox and add place-holder text on MouseEnter and remove on MouseLeave events. In this case place-holder's text looks like original text.. You can experiment with Foreground property, but truth me - you will not be satisfy.

Let my suggest other way. You can use AdornerLayer for host the place-holder text. In this case you should create class that is inherit from Adorner and this class should show your place-holder text on AdornerLayer. I've create little sample that demonstrate this.

Unfortunate, AdornerLayer doesn't presented over any Popup controls. So this solution isn't worked if you put our customized TextBox control in any Popup and as item in Menu or ComboBox controls.

Performance degrades in your Silverlight App!? What can you do?

2009-10-16T12:15:00.000-07:00

Some time ago I had written Silverlight app and I confronted with difficulties of difference between WPF and Silverlight :). When I had vanquished mismatches I found that performance of my app was serous degraded. I have done a little investigate of ways that can help to correct this issues.

MaxFrameRate
EnableGPUAcceleration & BitmapCash
CompositionTarget.Rendering

MaxFrameRate - presents the maximum number of frames that Silverlight can render per second. The default value is 60 second. I've set 30 in my app - looks pretty. This property likes DesiredFrameRate in WPF. Target is clear - reduce frame rate. It is useful when more animations are started in Silverlight app.
You can set it from Silverlight code:

App.Current.Host.Settings.MaxFrameRate=30;

or as parameter of object on HTML page:

<param name="framerate" value="30">

Pay attention there is a mismatch naming in Silverilght code and HTML. Why is it? You can read there.

EnableGPUAcceleration & BitmapCash - allows to cache visual object when it is possible. You should switch on EnableGPUAcceleration that Cache has any effect. This approach is useful when your app has opacity or transform operations applied to it.
You can set it from Silverlight code:

You can't change it from Silverlight because it should be set before app's initialization.

or as parameter of object on HTML page:

<param name="EnableGPUAcceleration" value="true" />

and set CacheMode. In current moment BitmapCache is supported only.
You can set it in C# code:

LayoutRoot.CacheMode = new BitmapCache();

or in XAML:

<Grid x:Name="LayoutRoot" CacheMode="BitmapCache">

Some objects don't look well (high-resolution images for example) you can increase RenderAtScale property of BitmapCache class for avoid this mess. Default value of this property is 1, when I set 4 (like MSDN's samples) quality restores but performance degrades again. A value between 2-3 is god for my app.
You can set it in C# code:

LayoutRoot.CacheMode = new BitmapCache
{
RenderAtScale = 2.5,
};

or in XAML:

<Grid x:Name="LayoutRoot">
<Grid.CacheMode>
<BitmapCache RenderAtScale="2.5" />
</Grid.CacheMode>
</Grid>

CompositionTarget.Rendering - this event rises before the objects in the composition tree are rendered. How does it can help? In common case - doesn't. But if you zoom your object in app (or in same other manner move out of bounds some item) - it is very useful. Look in my case:
First - subscribe event handler's method in constructor of your main window:

CompositionTarget.Rendering += new EventHandler( OnCompositionTargetRendering );

Second - handler method:


private void OnCompositionTargetRendering( object sender, EventArgs e )
{
//--- Start 1 -- //
foreach ( GalleryItem item in xGalleryCanvas.Children )
{
 if ( Visibility.Collapsed == item.Visibility )
 {
  item.Visibility = Visibility.Visible;
 }
}
//--- End 1 -- //
//--- Start 2 -- //
if ( _isZoomed && 0 < rect =" new" visibleitems =" VisualTreeHelper.FindElementsInHostCoordinates(" f =""> f.GetType() == typeof( GalleryItem ) );

 foreach ( GalleryItem item in xGalleryCanvas.Children )
 {
  if ( !visibleItems.Contains( item ) )
  {
   item.Visibility = Visibility.Collapsed;
  }
 }
//--- End 2 -- //
}

Some explanation: You should ascertain that all items are visible (block 1).
Note: Dependency property works not so good as in WPF. So you should change Visibility only of collapsed items. In other case you serious reduce the performance.
Use mix of FindElementsInHostCoordinates() of VisualTreeHelper and LINQ for create collection all visible items in current moment and collapse all other items (block 2).

Promise these three approaches can help as these help me.

PS: Recently I've found useful tips of Silverlight performance. You can read it there - Performance Tips.

Trips&Ticks: Do you know how you can unsubscribe from anonymous method?

2009-08-12T07:20:00.000-07:00

Anonymous Methods is a useful feature which we receive in Framework 2.0. It allows to easy pass a small code block as a delegate parameter (you can set a large block code but this code will be harmful because it is complex and isn't clear for perception). For example:

button1.Click += delegate
{
 MessageBox.Show( "Anonymous" );
};

But I have one trouble. What can I do if I want to unsubscribe from event. Seems it is subscribed finally, isn't it?.. Noup! If we declare instance of delegate before define we can unsubscribe a event from this delegate in the code block. For example:

EventHandler handler = null;

handler = delegate
{
 MessageBox.Show( "Anonymous" );
 button2.Click -= handler;
};

button2.Click += handler;

So if we click on button1 we receive message box always. If we click on button2 we receive message box once.

LINQPad (new version) - nice tool that can help you to stady LINQ.

2009-07-29T22:21:00.000-07:00

LINQPad is nice tool that can help you to study LINQ. I have read firs overview of this tool. Absence auto-complete grieves most people. Auto-complete is present in new version. This option requiring payment. IMHO: auto-complete is more detrimental than efficiency for studying (but very useful for work).
But I want say not about that. LINQPad is obtain other interesting feature. Author of this tool Joseph Albahari with your brother had written book "C# 3.0 in a Nutshell" and he added LINQ samples from this book to LINQPad. You can not only investigate different case moreover you can see how it look in lambda and IL code.

Investigate these samples in IL code should be very interesting ;)

Do you know about LINQ that.. ?

2009-07-19T02:07:00.000-07:00

Do you know about LINQ to SQL that attribute is more important than value? What is it mean? My friend have found interesting relation. He had written LINQ to SQL where he checked a column value to null but he was disappointed - it wasn't worked if it was need. He had null values in set but LINQ code didn't see they (He had written simple test code with foreach - it worked). After some investigate he has found that trouble in mapped data. Particular property was marked ColumnAttribute with set CanBeNull property false. So LINQ implicitly optimizes him code regards attribute's value (skips the check to null).
PS: It shows that we should be careful to small thing.. because small things can implicitly brings a big and strange problems.

Do you know about nested class that.. ?

2009-07-19T01:40:00.000-07:00

Download source files - here

Do you know about nested class that you can make nested class as partial? Yep, You can do it. Exactly your main class should be partial too.

This whimsical binding. TwoWay Binding to DataContext. Binding in WPF part 3.

2009-06-16T12:52:00.000-07:00

I often use Binding to DataContext. It is one of the main advantage of WPF. In most case I set custom class inherit of DependencyObject (for support DependencyProperty) and I have some like next code:

<StackPanel>
  <TextBlock Text="{Binding Path=Id}" />
  <TextBlock Text="{Binding Path=Name}" />
  <TextBlock Text="{Binding Path=Surname}"/>
...
 </StackPanel>

But sometime I set a simple type for example string. For this case I can implement next Binding:

<TextBlock Text="{Binding}" />

Note: Pay attention, when we bind directly to DataContext I have written a short form (only 'binding' keyword).

But when I try to implement TwoWay Binding to DataContext. I have exception - "Two-way binding requires Path or XPath.". It cannot set a value from somewhere because it doesn't know where it came from. I can easy fix it. For example property IsChecked of CheckBox has request TwoWay Binding in metadata. For this case I have written next code:

<CheckBox IsChecked="{Binding Path=DataContext, RelativeSource={RelativeSource Self}}">

It is not so graceful, but it works.

Trips&Ticks: Set custom presented view for enum's fields in WPF.

2009-06-02T14:20:00.000-07:00

Download source files - here.
Download bin files - here.

How you know, Enum can have underlying type as byte, sbyte, short, ushort, int, uint, long, or ulong. Often and often we need to present a view of Enum's values in visual elements. Usually enum's name isn't smooth for human look. As I have said we can't set for example string as underlying type and apply it as presented view.. We can use converter inherit from IValueConverter but it isn't comfortably as we need to reimplement it each time when Enum's count or order will be changed. I have implemented a simple class inherits from Attribute for set human smooth presented view:

[AttributeUsage( AttributeTargets.Field )]
public class ViewEnumAttribute : Attribute
{
public ViewEnumAttribute( String view )
{
View = view;
}

public String View
{
get;
private set;
}
}

We set AttributeTargets as Field for restrict scope of our attribute. Use of attribute is very simple:

public enum MyEnum
{
[ViewEnum( "My View Value 1" )]
MyEnumValue1,
[ViewEnum( "My View Value 2" )]
MyEnumValue2,
[ViewEnum( "My View Value 3" )]
MyEnumValue3,
}

and we extract this value when it is need:

private static object GetEnumView( Type fieldType, string fieldName )
{
FieldInfo info = fieldType.GetField( fieldName );

if( null != info )
{
foreach( ViewEnumAttribute attribute in info.GetCustomAttributes( typeof( ViewEnumAttribute ), false ) )
{
return attribute.View;
}
}

return fieldName;
}

For more details of realization you can look in attached above source files.

Implementing support of own child/children in WPF control.

2009-05-18T12:55:00.000-07:00

Download source files - here
Download bin files - here

The best way for use child/children in WPF is customize any control with property for child/children that inherit from Control (for example ContentControl or ItemsControl). Control has wide possibility of customizing through ControlTemplate. But sometime we want to have a specific behaviour of child/children (for example if we want to implement MDI container any other specific container). What should you do for implementing this behaviour? I will show major steps in sample of simple custom panel that is inherited from FrameworkElement.

First of all you should add property according type that will be contain child/children. I use Children property in my sample. It is list of UIElement. I use ObservableCollection because I need to react to collection change.
You should see to show child/children in your control, you should override int VisualChildrenCount and Visual GetVisualChild( int). These method and property should get value accordingly with child/children property (child/children's count and this/these element/s according to index).
Your app can correct build now but still nothing shows in app when it is run. It is happened because child/children doesn't/don't know their size and position on parent. You should override Size MeasureOverride(Size) for pass size (and calculate DesiredSize in child) to child's element and Size ArrangeOverride(Size) for pass position on parent. When you run app again you can see child/children in your custom control. You should point out to sizes that are returned in these method, MeasureOverride's size says to parent DesiredSize of your custom control and ArrangeOverride says to parent square that were taken.
Now you can see that your custom control is run correct, but when you try to interact with their child/children you can see that interact is fail. It is happened because child/children property isn't/aren't added to visual tree of your custom control. AddVisualChild(Visual) method helps you in this. The best way is realized this behavior in property changed method for child or collection changed method for children. Pay attention that property changed isn't called for default value for your child/children property. We have some other reason set null as default value, but I say below about it.
If you test your custom control more careful you can observe that interaction isn't complete. Yeah, visual interaction you have already implemented, but logical isn't complete. How can you observe it? Easy, try to use attached and inherit properties or DataContext - they don't work. You should add child/children to logical tree of your custom control. AddLogicalChild(Object) helps. You can call this method together with AddVisualChild.
Be careful, if you want to remove element from child/children you shouldn't remember that this element should be removed from visual tree and logical tree. RemoveVisualChild(Visual) and RemoveLogicalChild(Object) help you in this.
Interaction works correct now, but you can see new trouble, if you add/remove child/children in run-time you can't see any visual effect until do any change of size in app. It is happen because your custom control knows nothing about this add/remove action. If you are implementing child you can add AffectsArrange and AffectsMeasure flag to metadata of child property, they mean that custom control should do arrange and measure after each property change. If you are implementing children you should call InvalidateVisual() after each collection change. Added/Removed item shows/disappears immediately now.
If you want set child/children property through XAML you should explicitly set your child/children property. You can apply to your custom control attribute ContentPropertyAttribute. So you can implicitly set your child/children property.
In point #4 I have promised to say why you can't set default value no null. Pay attention that Dependency property is static member of class, so refer of one default value is added to all instances of your custom class. So you should use type that inherit form ValueType as type of dependency property or reinitialize default value in constructor (You should chose second way:).
My coworker have found interesting trouble with RightToLeft support. His custom control can correct support RightToLeft only after he overrides LogicalChildren property. I can't reproduce it, but want to inform about possible trouble and solution for it.

I have written detailed road map with explanations. If some details aren't clear you can download sample with source code (case with children is implemented there).
Good luck!

Some samples of "101 LINQ Samples" aren't valid.

2009-05-12T06:55:00.000-07:00

My previous post (101 LINQ Samples) refers to very interesting samples. But I didn't pay attention that it is announcement as "future" features. So some of these samples aren't valid (were not implemented).
I'm not one found this trouble, in this forum thread shows what we can use instead of Fold (Aggregate) and EqualAll (SequenceEqual), we should use own realization according to situations for some other operations (SelectMany, Combine).

"Everybody lies" (c) House M.D.

101 LINQ Samples

2009-05-07T08:58:00.000-07:00

Sometimes I work with LINQ. So I have completed a task and after some time I should try recall my knowledge of LINQ for new task. It is inconveniently as I should search some info time and again. I have found a great simple LINQ samples. It is very useful and clear for novice. So I can avoid a new recall next time :).
This document locates there - LINQ Samples.

Trips&Ticks: Do you know how you can break text in any text control of WPF?

2009-04-21T00:15:00.000-07:00

Seems it is easy - we can use a LineBreak in code or as XAML element, but what can we do if we want to present this in attribute of XAML? Little searching shows that we should use XSLT and hexadecimally encoded value to present a literal.
<TextBlock Text="Line 1
Line 2" />

Trips&Ticks: Do you know how can you obtain access to nested types through XAML?

2009-04-13T06:19:00.000-07:00

Download source files - here.

XAML is a declarative XML-based language created by Microsoft which is used to initialize structured values and objects. I have already written how we can obtain access to properties of instance that located in other properties here (I have described binding's potential). But what can we do if we need to access to nested type? Which syntax should me use? It is easy: "+" indicates nested type in XAML:

local:MultiLevelButton+NestedInfo.NestedName

A lot of code snippets you can see in sources.

OnTime desktop light client.

2009-03-03T23:47:00.000-08:00

Download source files - here.
Download binary files - here.

My previous customer uses OnTime as bts. It is very slowly tool. I hated it! I tired to wait any respond from this app. I have created a little and more fast tool for self using. This tool ins't complete (I have stopped to work with this customer and I can't have an access to bd for continue implementation).
Next issues need a fix:

SQL exception isn't handled infrequent :)
Icons aren't useful. Useful tooltips correct this defect ;)
Attachment download works in some thread that GUI (It is shameful, but I haven't had time, really)
App works readonly.
Sort and Search hasn't implemented.
We can work with self issues only.

Advantage:

It is really more fast tool than official.
Persist state doesn't store in bd. It saves in current PC only.

Axosoft releases new version (9.0). It is more fast than previous (8.0). But it is still no enough.
If you want to implement some features or to fix bugs you need to know that for correct run sources you need to set connection string in the next files:

app.config
Settings.Designer.cs
OTData.dbml
and Settings.settings in two points.

I have changed my connect string to "your_connecting_string" for more handy replace ;).

Trips&Ticks: Do you know how you can extract various instances of one object out of resources in WPF?

2009-02-03T12:37:00.000-08:00

Download source files - here

I often use a style&template that is magnificent possibility of WPF. It allows to define one style out of resources to many elements. I can easily define instance of some object in resources and extract it there where I require. But it has one limitation:
For example for following:

XAML:
<Button x:Key="ButtonPrototype" />

C#:
Resources["ButtonPrototype"];

- returns always one instance (like Singlton Pattern). But what can I make if I require more than one such object? It isn't problem as XAML is very flexible and x:Shared attribute eliminates this trouble. Following code will extract various instances:

XAML:
<Button x:Key="ButtonPrototype" x:Shared="False" />

C#
Resources["ButtonPrototype"]

PS: In my opinion last realization shares traits with Prototype Pattern.

Bind to many method simultaneously. Binding in WPF part 2.

2009-01-10T02:42:00.000-08:00

Download source files - here
Download binary files - here

Target:
We have some views that have as source one shared collection. They are located in any ItemsControls (ListBoxs in my case). Those views pass form different parametrized methods (we use the ObjectDataProvider and bind to a method possibility for this purposes). How can we implement one control element's property for affect on those views? We have restricts - it is needed to make in XAML code.

Problem:
How can we pass a value of control element as parameter in bind to a methods?

Solution:
First of all we should declare some (I used "two", so I will write in next time "two" instead of "some") ObjectDataProvider objects.


<ObjectDataProvider ObjectType="{x:Type local:CItems}"
MethodName="GetMax" x:Key="max" >
<ObjectDataProvider.MethodParameters>
<system:Int32>3</system:Int32>
</ObjectDataProvider.MethodParameters>
</ObjectDataProvider>

<ObjectDataProvider ObjectType="{x:Type local:CItems}"
MethodName="GetMin" x:Key="min" >
<ObjectDataProvider.MethodParameters>
<system:Int32>3</system:Int32>
</ObjectDataProvider.MethodParameters>
</ObjectDataProvider>

Bind those objects to views:



<ListBox ItemsSource="{Binding Source={StaticResource min}}" />
<ListBox ItemsSource="{Binding Source={StaticResource max}}" />

Now we need to create a binding to control element's property that has affect to both those data provider. We use MultiBinding with Mode is set OneWayToSource for this purpose. We should implement Converter of MultiBinding. Since we set Mode as OneWayToSource we need only ConvertBack method:



public Object[] ConvertBack( Object value, Type[] targetTypes, Object parameter, CultureInfo culture )
 {
  Int32 cnt = targetTypes.Length;
  Object[] result = new Object[ cnt ];
  String str = value.ToString();

  if( !String.IsNullOrEmpty( str ) )
  {
   Int32 index = Int32.Parse( value.ToString() );

   for( Int32 i = 0; i < cnt; ++i )
   {
    result[ i ] = index;
   }
  }

  return result;
 }

Note: We should unbox value to Int32 other case value isn't correctly passed to method of data provider.

Now we can easy implement this MultiBinding our XAML code:



<ComboBox.Text>
<MultiBinding Mode="OneWayToSource" Converter="{StaticResource artfull}">
<Binding Source="{StaticResource max}"
Path="MethodParameters[0]"
BindsDirectlyToSource="true"
UpdateSourceTrigger="PropertyChanged"
/>
<Binding Source="{StaticResource min}"
Path="MethodParameters[0]"
BindsDirectlyToSource="true"
UpdateSourceTrigger="PropertyChanged"
/>
</MultiBinding>
</ComboBox.Text>

Now when Text property of ComboBox is changed that views will be updated. Easy and nice :). If some details isn't clear - source and binary files were attached in the beginning of article.

Trips&Ticks: Do you know how you can use GroupName property of RadioButton for ToggleButton in WPF?

2008-12-06T16:15:00.000-08:00

We can use GroupName property for mutually exclusive RadioButton but what can we do if we want to use mutually exclusive ToggleButton? ToggleButton doesn't have like ability. Please, do look in RadioButton what can you see? Exactly, RadioButton is inherit from ToggleButton so we can set in Template property ControlTemplate of ToggleButton. So our RadioButtons will be look like ToggleButtons besides will have GroupName property.

Trips&Ticks: Do you know how you can cast Object to AnonymousType?

2008-11-21T12:28:00.002-08:00

I experimented with LINQ in my private project and question that was showed in title took me. I had next situation:

I set list in one method:

private void SetList()
{
SomeList.ItemsSource = ( from someTable in data.SomeTable
   select new
   {

someTable.Id,

someTable.Name,

              Priority = someTable.Priority,

} );
In other method I want retrieve Id of selected item. How can I do it? I have found interesting solution in blog of Tomas Petricek.

private Int32 GetID()
{

Object selectedItem = DefectList.SelectedItem;

if( null != selectedItem )

       var item = Utility.Cast( selectedItem, new

           Id = 0,

           Name = String.Empty,

           Priority = String.Empty,

           } );

           Int32 id = item.Id;

}
}
public static T Cast( object obj, T type )
{

return (T)obj;
}

PS: As for me the best way is:

implement class with three like property.
create collection with items of this class.
set in ItemsSource new created collection.
now we can easy case Object to this class.

Such different paths. Binding in WPF part 1.

2008-11-18T13:43:00.000-08:00

Download source files - here

We pleasure to using Binding in WPF. But all ways of using have we known? Only direct binds to dependency property like next code?

<TextBlock Text="{Binding Path=Height, ElementName=myButton}">

This is poor. We can bind to property of value's property. How?
Easy:

<TextBlock Text="{Binding Path=Background.(SolidColorBrush.Opacity), ElementName=myButton}"/>

and

<TextBlock Text="{Binding Path=(Button.Content).(TextBlock.FontSize), ElementName=myButton}"/>

In attached sample I show how we can use this for EventTriggers.

Trips&Ticks: Do you know how do you need to change properties of local file when it will be loaded, using a Relative Uri?

2008-10-22T07:41:00.000-07:00

When I had tried to use Relative URIs for local files I found next trouble - resource wasn't found in my app. Solution for this problem is next actions: we should open properties of local file and change flag named "Copy to Output Directory" from "Do not Copy" to "Copy always".
Easy and logically.

PS: Nice article about URI in WPF - Pack URIs in Windows Presentation Foundation

Really multiUI window in WPF project.

2008-10-15T23:46:00.000-07:00

Download binary file - here
Download source files - here

Introduction.
WPF presents new way to implement visual appearance of application. We can implement it in XAML and C# files both or separately. We use Application.LoadComponent( Object, Uri ) method for load XAML files where "Uri" presents way to XAML file. So we can manipulate visual appearance presented in XAML's files load different XAML's files.

Note: We can't use x:Class attribute for root node in XAML's files. In this case compiler automatic generates C# code (in *.g.cs file) and those classes will be conflicted (more precisely - some automatic generated members will be conflicted). Thus we can't use x:Code and describe to events in XAML's files (code for support those actions were implemented in *.g.cs files).

Note: Class have been generated in XAML's file (more precisely - in *.g.cs) is normal class likes class have been generated in C# code and even we can inherit a custom class from it.

My sample.
My sample presents two mode for manager and worker that to show the personal's information. We load different XAML's files against of mode. First we show dialog window that propose to choose behaviour.

Different XAML's contains different class instants for present data:
PeopleEx (People - for worker) - presents data of personnel (less for worker and more for manager).
ManagerInfoPresenter (WorkerInfoPresenter - for worker) - get a information (different for other mode).
ManagerCapacityShow (WorkerCapacityShow - for worker) - show a diagram. It is fake but it is different for other mode.

We can implement different controls with one name in other XAML's files (for example "InformCheck" or "CapacityShow"). We found those controls in XAML's files to use FindName(String) method and we can handle some events of this controls.

    CheckBox informer = (CheckBox)FindName( INFORMCHECK_NAME );
     informer.Checked += new RoutedEventHandler( OnInformerChecked );
     informer.Unchecked += new RoutedEventHandler( OnInformerUnchecked );

We can apply to different class members to use base class (like m_CapacityShow member) or interface (like m_InfoPresenter member).

    if( AppMode.Manager == appMode )
      {

... m_InfoPresenter = new ManagerInfoPresenter();

}
      else
      {

... m_InfoPresenter = new WorkerInfoPresenter();

}
      ...
      m_CapacityShow = (Image)FindName( CAPACITYSHOW_NAME );

Summary
We can really create one class window for two (or more) behaviour of application. We don't hide any controls or elements we don't load they! It is elegant way to dynamic create application.

Little deception of List.ForEach(Action action)

2008-10-12T02:25:00.000-07:00

I use foreach statement really often. It is useful and more compact than for. (This way is fast in same case but in same case it is slowly for performance. But I want say not about that). List<T> class has ForEach(Action action) method I thought that its implementation (and behaviour) is like foreach statement (I make this conclusion, based on the name of method) but I was confused. I have looked to Net. Reflector and saw next code:

public static void ForEach(T[] array, Action action)
{
if (array == null)
{
throw new ArgumentNullException("array");
}
if (action == null)
{
throw new ArgumentNullException("action");
}
for (int i = 0; i < array.Length; i++)
{
action(array[i]);
}
}

ForEach(Action action) method behaviour likes for statement behaviour. And I can use it like for. For example I can change main collection during execution action delegate.

My version of Snoop (+ 2 features) of WPF

2008-07-30T14:46:00.000-07:00

I think that every WPF developer knows that is Snoop. This is helpful tool (with source code (!!) ) for visual debugging of WPF's app at runtime. It is good but I was in need of some expansions.

I needed to see Template of controls in visual tree.
I needed to keep a/some couple (value and property) of control in visual tree.

I implemented this issues for self purpose and want to impart this to all.

At first. My coworker Ivan and ex-coworker Eugene implemented like issue. But their solution didn't satisfy me. It had low performance. I re-implement it and in my solution convert to xaml come true after click to "Show XAML!" button only. It increase performance in comparison with previous solutions.

For second feature I used code of Beatriz Costa that allows you to drag and drop items between data bound ItemsControls (I added a little modification for my purpose only). I added new PropertyGrid. We can drag a item from main PropertyGrid to keep PropertyGrid.

In last PropertyGrid property saves relation with its owner even if it contains different owners of properties.

Here you can find the project with this features built using VS2008.

Enjoy ;)

Correct use ItemsSource in WPF for controls inherited from ItemsControl

2008-06-05T13:30:00.000-07:00

I sometimes read MSDN forums of WPF. I have founded post with interesting problem. I was interested this trouble.

We can download sample from there. Pay attention that ListView have strange behavior: pressing "s" moves the focus to the next item. I was interested this problem and little investigate it. This action relations with search functionality. If we don't need search functionality we can easy fix it, override ToString() method:

public override string ToString()
{
return string.Empty;
}

FYI:
If you need more details why does it do, you can read next:

After you type letter 's', next methods were called:
...................
- void OnTextInput( TextCompositionEventArgs e ) of ItemsControl;
- bool DoSearch(string nextChar) of TextSearch;
- int FindMatchingPrefix(ItemsControl itemsControl, string primaryTextPath, string prefix, string newChar, int startItemIndex, bool lookForFallbackMatchToo, ref bool wasNewCharUsed) of TextSearch;

- string GetPrimaryText(object item, BindingExpression primaryTextBinding, DependencyObject primaryTextBindingHome) of TextSearch

private static string GetPrimaryText(object item, BindingExpression primaryTextBinding, DependencyObject primaryTextBindingHome)
{
//item is EmployeeInfo (!!)
DependencyObject obj2 = item as DependencyObject;

if (obj2 != null) // false
{
string str = (string) obj2.GetValue(TextProperty);
if (!string.IsNullOrEmpty(str))
{
return str;
}
}
if ((primaryTextBinding != null) && (primaryTextBindingHome != null)) //false
{
primaryTextBinding.Activate(item);
return ConvertToPlainText(primaryTextBinding.Value);
}
return ConvertToPlainText(item); //It was called
}

-string ConvertToPlainText(object o) of TextSearch

private static string ConvertToPlainText(object o)
{
FrameworkElement element = o as FrameworkElement;
if (element != null) //false
{
string plainText = element.GetPlainText();
if (plainText != null)
{
return plainText;
}
}
if (o == null) // false
{
return string.Empty;
}
return o.ToString(); //return "SDKSample.EmployeeInfo"
}

- In this FindMatchingPrefix method we prepare this string as follows
........................

string str2 = GetPrimaryText(obj3, bindingExpr, itemsControl);
if ((str2 != null) && str2.StartsWith(str, true, culture)) //"SDKSample.EmployeeInfo" is started with "s" ;) (!!!!!)
{
wasNewCharUsed = true;
num = num4;
break;
}
........................
return num;

- and in the DoSearch(string nextChar) method
........................

int itemIndex = FindMatchingPrefix(this._attachedTo, primaryTextPath, this.Prefix, nextChar, startItemIndex, lookForFallbackMatchToo, ref wasNewCharUsed);

if (itemIndex != -1)
{
if (!this.IsActive || (itemIndex != startItemIndex))
{
object item = items[itemIndex];

this._attachedTo.NavigateToItem(item, itemIndex, new ItemsControl.ItemNavigateArgs(Keyboard.PrimaryDevice, ModifierKeys.None)); //wrong code is started
this.MatchedItemIndex = itemIndex;
}

........................

Nothing is perfect..

Problem with focus scope in WPF.

2008-05-12T12:46:00.000-07:00

WPF contains interesting static class FocusManager. This class (more precisely: its static method SetIsFocusScope) allows to set the specified DependencyObject as a focus scope (You can read more about it here).
But we have a limitation that didn't describe in MSDN (or more precisely, I not found). We can't use all controls that were inherited from ButtonBase in this focus scope, as these controls can't capture Keyboard.Focus in this focus scope. In OnLostMouseCapture method validates whether button is located in main window's focus scope. So if it isn't, control loses Keyboard.Focus (its be after Click event).
From information from my co-worker, this behaviour will be added for buttons correct works in ToolBar.
I think that a solution of MS could be more graceful for trouble of ToolBar.

Inherit properties

2008-05-05T13:39:00.000-07:00

When I investigated WPF feature, I was interesting how use inherit property (If consider that Binding is low performance feature). I used these properties as RegisterAttached only. I have write some test samples but these didn’t work to my of the confuse. Little search in MSDN founded the root of problem. It locate in end of inherit property document, after eulogy powerful this feature.

Note:
Although property value inheritance might appear to work for nonattached dependency properties, the inheritance behavior for a nonattached property through certain element boundaries in the run-time tree is undefined. Always use RegisterAttached to register properties where you specify Inherits in the metadata.

So, this is no surprise that my samples didn’t work. You can read more here.

Cider vs VS2008's builder. Just for fun

2008-04-16T05:09:00.000-07:00

I wrote little test sample with using WPF. I added a custom class (inherit from Button) in sample's namespace. I needed to add control in application.

Taking into account my previous work experience with the implement controls, I wrote like next xmlns:local="clr-namespace:WpfApplication1;assembly=WpfApplication1" ,

I confused.

Project didn't build. It saw that couldn't find my custom class in adjusted XML namespace. In this case to my great surprise Cider parsed all correct and show Button in my case (my custom class was inherit from Button) even add correct a method for event handler.

I miss when added full type describe of namespace. In this case I had to write next: xmlns:local="clr-namespace:WpfApplication1"

Note:

If namespace of application set to use XmlnsDefinition (for example: [assembly: XmlnsDefinition( "http://www.mySite.com", "WpfApplication1" )] in AssemblyInfo.cs) and accordingly we must to write xmlns:local="http://www.mySite.com" in app. This sample isn't built and Cider doesn't parse it. We should use like code in an external dll only.

ItemsSource tips & tricks

2008-04-13T11:46:00.000-07:00

Describe problem.

When we wish to implement the mechanism Drag&Drop of Children for our control in WPF, particularly that our control contains children in its logical tree (in other case attached and inherit properties work incorrect sometimes). Let that control template contains some other controls inherit from ItemControl. We wish add some children to this inherit from ItemControl controls. What can we do?

If we use Items that we have a disagreeable surprise - we should add items to logical tree of internal control (previous to remove from our control's logical tree - it is the problem described above). But we can create collection inherit of IEnumerable and it is bound to ItemsSource of internal controls - all will be worked nice.

Note:

If property ItemsSource isn't equal 'null' that we can work with Items in read-only mode. If ItemsSource equal 'null' that we can full use Items (It is empty after those actions). If we need dynamic change of items we can implement INotifyPropertyChanged interface. The better solution is to use ObservableCollection for this purpose.

Deployment SVN (Subversion) for Windows as Home Version Control System.

2008-04-08T14:52:00.000-07:00

I need to use Version Control System in home. It is have requirement: should be free and for Windows XP. I selected the SVN (http://subversion.tigris.org/) version at 1.4.8.12137 (It’s latest in this moment).

After installation in InstalataionFolder (default: “C:\Program Files\Subversion” you can select another) you should added repository folder and start server of SVN.

You can register repository folder to use svnadmin. First off all you should create repository folder – RepositoryFolder (I used “D:\Programming\svn”)

You do start command window (cmd.exe) in InstalataionFolder\bin and do type next command: svnadmin create "RepositoryFolder" (for example in my case: svnadmin create "D:\Programming\svn").

Note: Pay attention, we use some slash of Windows (“\”).

Now you should create service for automatic start the svn server. We use “sc.exe” for this target. “sc.exe” is located in system folder (It’s “C:\Windows\Sytstem32” in my PC). Create service: sc create svn binpath= "InstalataionFolder\bin\svnserve --service -r
"RepositoryFolder" displayname= "SVN Server" depend= Tcpip start= auto

(In my case “sc create svn binpath= "C:\Program Files\Subversion\bin\svnserve --service -r "D:\Programming\svn" displayname= "SVN Server" depend= Tcpip start= auto”).

Note: Pay attention, we use two symbols of minuses before “service” and set space after each equals sign.

After we should uncomment “password-db = passwd” section in configure file – RepositoryFolder\conf\svnserve.conf (D:\Programming\conf\svnserve.conf in my case) and configure access to svn. We uncomment “auth-access” and uncomment and change value to “none” for “anon-access” (I deny anonymous access to svn).

You should create pair login-password in section [users] of file “RepositoryFolder\conf\passwd” (D:\Programming\conf\passwd in my case)

Now, you can start “SVN Server” service (Press Win+R and type in Run window the “services.msc” and start “SVN Server” or other with name that you have set).

And the end of article, I use a TortoiseSVN (http://tortoisesvn.tigris.org/) as client.

Correct use DataTemplateSelector.

2007-09-03T22:44:00.000-07:00

In the many inherited from FrameworkElement in WPF contain a useful dependency property *TemplateSelector type of DataTemplateSelector. It can set our inherit from DataTemplateSelector class and override the method SelectTemplate(). This allow dynamic generate template for a content. Content-data we can get a elementary binding. And now feature: we can use all binding (even that what refet to ElementName), except TemplateBinding, therefore RelativSourceMode doesn't equal TemplatedParent.

My Vista sidebar gadget :)

2007-07-25T06:07:00.000-07:00

I create Vista sidebar gadget for UA gadget competitions. It was adds to follow page iTV Watcher.
I had wanted to use SilverLight 1.0 (version 2.0 wasn't accessible in this time) for this purpose but I can't overcome a problem with event if to use Silverlight in sidebar of Vista. So I must was to use a simple JavaScript (It was missed some WPF-like animations feature, but it work correct).
Enjoy!

"Cruel" colors substitution.

2007-07-25T03:14:00.000-07:00

Sometime we need custom one or more brush of control in WPF. If template is not available and in base template used system brush, we can use this workaround (example for ListBox):

<ListBox>
<ListBox.Resources>
<SolidColorBrush x:Key="{x:Static SystemColors.HighlightBrushKey}" Color="Maroon" />
<SolidColorBrush x:Key="{x:Static SystemColors.ControlBrushKey}" Color="Maroon" />
<SolidColorBrush x:Key="{x:Static SystemColors.HighlightTextBrushKey}" Color="White" />
<SolidColorBrush x:Key="{x:Static SystemColors.ControlTextBrushKey}" Color="White" />
</ListBox.Resources>
<ListBoxItem>blah-blah</ListBoxItem>
<ListBoxItem>blah-blah</ListBoxItem>
<ListBoxItem>blah-blah</ListBoxItem>
</ListBox>

Custom style for a class which is inherited from the class of Selector

2007-07-25T01:59:00.001-07:00

We need set own custom style or template for item of control which was inheritance from abstract class 'Selector' (for example: ComboBox, ListBox, TabControl) in WPF.
We can use two way:
1) We can add in control's resource some style and template. But it isn't good way, because these styles and templates have access only in boundary of control.
2) We can use inheritance from Selector ItemContainerStyle dependency property and set in it new style value.

Correct works of MultiDataTrigger.

2007-07-25T01:38:00.000-07:00

Sometimes we will be use a few MultiDataTrigger in WPF and them contain one identical binding. As practice shows better way is write identical binding to last in the list of condition, in other case MultiDataTrigger works not always. For the other types of MultiTriggers the it was unchecked, although scarcely it isn't identical..

Add my avatar...

2007-07-24T23:27:00.000-07:00