How to detect broken WPF Data binding?

Question

While trying to answer a question in the vicinity 'Unit Testing WPF Bindings' I had the following niggling question..
What's the best way to find if you have WPF Data Binding wiring setup incorrectly (or you just broke something that was wired up correctly) ?

Although the unit-testing approach seems to be like Joel's 'ripping off your arm to remove a splinter'.. I am looking around for easier less Overhead ways to detect this.

Everyone seems to have committed themselves to data binding in a big way with WPF.. and it does have its merits.

Answer 1

Best I could find...

How can I debug WPF Bindings? by Beatriz Stollnitz

Since everyone can't always keep one eye on the Output Window looking for Binding errors, I loved Option#2. Which is add this to your App.Config

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <system.diagnostics>
    <sources>
      <source name="System.Windows.Data" switchName="SourceSwitch" >
        <listeners>
          <add name="textListener" />
        </listeners>
      </source>

    </sources>
      <switches>
        <add name="SourceSwitch" value="All" />
      </switches>

      <sharedListeners>
        <add name="textListener"
        type="System.Diagnostics.TextWriterTraceListener"
        initializeData="GraveOfBindErrors.txt" />
      </sharedListeners>

      <trace autoflush="true" indentsize="4"></trace>

  </system.diagnostics>
</configuration>

Pair that up with a good regex scan script to extract out relevant info, that you can run occasionally on the GraveOfBindErrors.txt in your output folder

System.Windows.Data Error: 35 : BindingExpression path error: 'MyProperty' property not found on 'object' ''MyWindow' (Name='')'. BindingExpression:Path=MyProperty; DataItem='MyWindow' (Name=''); target element is 'TextBox' (Name='txtValue2'); target property is 'Text' (type 'String')

Answer 2

In .NET 3.5 it was introduced a new way to specifically output tracing information about specific data bindings.

This is done through the new System.Diagnostics.PresentationTraceSources.TraceLevel attached property that you can apply to any binding or data provider. Here is an example:

<Window x:Class="WpfApplication1.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:diag="clr-namespace:System.Diagnostics;assembly=WindowsBase"
    Title="Debug Binding Sample"
    Height="300"
    Width="300">
    <StackPanel>
        <TextBox Name="txtInput" />
        <Label>
            <Label.Content>
                <Binding ElementName="txtInput"
                         Path="Text"
                         diag:PresentationTraceSources.TraceLevel="High" />
            </Label.Content>
        </Label>
    </StackPanel>
</Window>

This will put trace information for just that particular binding in Visual Studio's Output Window, without any tracing configuration required.

Answer 3

Here's a useful technique for debugging/tracing triggers effectively. It allows you to log all trigger actions along with the element being acted upon:

http://www.wpfmentor.com/2009/01/how-to-debug-triggers-using-trigger.html