Binding a C# property to a WPF validated Control

By Jerome at August 29, 2007 05:48 Tags: , ,

The DataBinding in WPF allows the binding of control properties to many things, like other control properties, arrays, data providers, ... But it can also bind a control property to a property defined by code on the C# side.

It is interesting to bind to C# property to be able to have the integrated WPF validation and still use a simple property from the code. In that case, I wanted to have the validation of a TextBox displaying a DateTime object.

Here's how to do this.

On the C# side :


public partial class Window1 : Window

  public Window1() 
  {   
    MyDate = DateTime.Now;
    InitializeComponent();
  }
  public DateTime MyDate { get; set; }
}
 

Note that I'm using the latest C# 3.0 syntax to declare variable-less properties. This is compiler trick, the variable is still declared at compile time, but since I don't need to have a specific code in the get or set accessor, it can stay in this short form.

Now on the XAML side :


<Window ... >

  <TextBox Width="100" Height="20">

    <Binding Path="MyDate" RelativeSource="{RelativeSource Mode=FindAncestor,AncestorType={x:Type Window}}" UpdateSourceTrigger="PropertyChanged">

      <Binding.ValidationRules>

        <ExceptionValidationRule />

      </Binding.ValidationRules>

    </Binding>

  </TextBox>

</Window>

The interesting part here is the use of RelativeSource and the FindAncestor mode. Here, we're looking for the property MyDate from the nearest ancestor instance of the Window type, from the current instance.

This way, you'll have a validated date time in your property value. Just make sure you're checking that the value is really valid using the System.Windows.Controls.Validation class.

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About me

My name is Jerome Laban, I am a Software Architect, C# MVP and .NET enthustiast from Montréal, QC. You will find my blog on this site, where I'm adding my thoughts on current events, or the things I'm working on, such as the Remote Control for Windows Phone.