How to suppress the System.Windows.Data Error warning message

Hi,

When we use FindAncesstor in custom control template for binding internal elements property into its ancestor element, visual studio displays data warning messages in output window when binding engine meets unmatched target type during visual tree traversal though it does the proper binding when it receives expected target type during visual tree traversal. To suppress this data error warning messages, you should mention level of warning message trace in your library class.

Here is the simple data error that I am getting when I bind some commands in rich text box.

System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='System.Windows.Controls.RichTextBox', AncestorLevel='1''. BindingExpression:Path=Content; DataItem=null; target element is 'Button' (Name=''); target property is 'CommandTarget' (type 'IInputElement')
System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='System.Windows.Controls.RichTextBox', AncestorLevel='1''. BindingExpression:Path=Content; DataItem=null; target element is 'Button' (Name=''); target property is 'CommandTarget' (type 'IInputElement')
System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='System.Windows.Controls.RichTextBox', AncestorLevel='1''. BindingExpression:Path=Content; DataItem=null; target element is 'Button' (Name=''); target property is 'CommandTarget' (type 'IInputElement')
System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='System.Windows.Controls.RichTextBox', AncestorLevel='1''. BindingExpression:Path=Content; DataItem=null; target element is 'Button' (Name=''); target property is 'CommandTarget' (type 'IInputElement')
System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='System.Windows.Controls.RichTextBox', AncestorLevel='1''. BindingExpression:Path=Content; DataItem=null; target element is 'Button' (Name=''); target property is 'CommandTarget' (type 'IInputElement')
System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='System.Windows.Controls.RichTextBox', AncestorLevel='1''. BindingExpression:Path=Content; DataItem=null; target element is 'Button' (Name=''); target property is 'CommandTarget' (type 'IInputElement')

Solution, set data binding source switch level as critical in constructor of the class.

System.Diagnostics.PresentationTraceSources.DataBindingSource.Switch.Level = System.Diagnostics.SourceLevels.Critical;

Thanks,
Venugopal.

DataBinding In WPF

Today I will discuss about DataBinding that I have faced in my experience. please leave a comment and I'll cover them in my next post.

DataBinding is the technique of connecting controls and elements to the data. In the past, a programmer would write code both to initialize control from the variable and to set the variable into controls . In modern programing environments , the programmer defines a binding the control and variable , the binding automatically performs both the jobs.

Very often a data binding can replace an event handler, and simplifying the code. DataBinding are considered to have Source and Target. Here source is Data and Target is the Control and may be two controls will participate.

The bound property of the source need not be a Dependency property , but target property must be derived from the dependency object.

How can we bind data using {Binding} concept?

we can bind data between two elements or from resource collection. The following format is for bind with resource collections.

<!-- Resource Area-->
<Window.Resources>
<system:String x:Key="myvar">Hi , This is Binding </system:String>
</Window.Resources>

<!-- Bind With resource -->
//Method 1 (this method will bind whole object)
<TextBlock TextContent="{StaticResource myvar}" />

//Method 2 (this will bind particular property of object). it will display lenth property value of string .
<TextBlock Content="{Binding Source={StaticResource myvar}, Path=Length}" />

For Bind With Another Elements

<TextBlock Content="{StaticBinding Path=Length, ElementName=MyBox}" />
<TextBox Name="MyBox" />

Here textblock getting changes its content while typing the content on textbox.

Binding Modes

You can specify the mode property is separated from the path using comma.

Type of Mode

1. OneWay -From the picture label get the value from source textbox. But it wont affect textbox value while the change happens in the label.


2. TwoWay - From the picture Label get the from the Source textbox and also textbox will get the reflection while the change happens in the label.


3. OneTime - From the picture Label initialized from the source textbox but does not track changes .


4. OneWayToSource -if target property is not packed by a dependency property while source is . In that case we can use this mode.

DataContext

DataContext is inherited through the element tree , so if you set it for one element it is also applies to all the children of that element. For example if we set the binding in stackpanel. We can bound properties of all the control under stackpanel.

Example

<StackPanel DataContext=”{Binding ElementName=scroll}”>

<Label Content=”{Binding Path=Value, Mode=OneWay}”/>

<Button FontSize=”{Binding Path=Value, Mode=OneWay}”/>

</StackPanel>

Source Binding

Source binding is used to bind the class properties instead of element name . The ElementName Binding can bind Element to Element Binding like Label into TextBox like that .

For example .
MyClass is a class , it contain Property Named MyProperty. If you want bind this property into your control we can use like this .

“{Binding Source={x:Static g:MyClass}, Path=MyProprty}";
or
“{Binding Source={x:Static g:MyClass.MyProprty}}”;

Here path may be like this Path=””.

RelativeSource

This is other alternative way to binding markup using ElementName and Source .
Which lets you reference an ancestor element in the element tree or element itself.

For Example

"{Binding RelativeSource={RelativeSource AncestorType={x:Type StackPanel}}, Path=Orientation}"

Here ancestor type is StackPanel and its property is Orientation .

Enjoy !!!! I will cover in my next post regarding converter concept!.