Tuesday, November 24, 2009

Useful code snippets for WPF developer.

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.

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.

Thursday, November 19, 2009

Zoom and page changed events for FlowDocumentPageViewer

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:
  1. When I change the pages of the FlowDocumentPageViewer, my Rectangular highlighted area remains the same and it is not sinking with the Text.
  2. 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.

Monday, November 16, 2009

How to implement TextBox with PlaceHolder in WPF

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.

Friday, October 16, 2009

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

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.
  1. MaxFrameRate
  2. EnableGPUAcceleration & BitmapCash
  3. 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:


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">
<BitmapCache RenderAtScale="2.5" />

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.

Wednesday, August 12, 2009

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

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.

Wednesday, July 29, 2009

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

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 ;)

Sunday, July 19, 2009

Do you know about LINQ that.. ?

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.. ?

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.

Tuesday, June 16, 2009

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

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:

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

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.

Tuesday, June 2, 2009

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

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
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" )]
[ViewEnum( "My View Value 2" )]
[ViewEnum( "My View Value 3" )]

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.

Monday, May 18, 2009

Implementing support of own child/children in WPF control.

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.
  1. 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.
  2. 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).
  3. 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.
  4. 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.
  5. 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.
  6. 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.
  7. 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.
  8. 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.
  9. 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:).
  10. 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!

Tuesday, May 12, 2009

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

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.

Thursday, May 7, 2009

101 LINQ Samples

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.

Tuesday, April 21, 2009

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

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&#x0A;Line 2" />

Monday, April 13, 2009

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

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:


A lot of code snippets you can see in sources.

Tuesday, March 3, 2009

OnTime desktop light client.

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.
  • 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:
  1. app.config
  2. Settings.Designer.cs
  3. OTData.dbml
  4. and Settings.settings in two points.
I have changed my connect string to "your_connecting_string" for more handy replace ;).

Tuesday, February 3, 2009

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

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:

<Button x:Key="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:

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


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

Saturday, January 10, 2009

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

Download source files - here
Download binary files - here

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.

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

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 ObjectType="{x:Type local:CItems}"
MethodName="GetMin" x:Key="min" >

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:

<MultiBinding Mode="OneWayToSource" Converter="{StaticResource artfull}">
<Binding Source="{StaticResource max}"
<Binding Source="{StaticResource min}"

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.