BindingExpression.UpdateSource swallows exception

Question

The following code snippet is a simplified version of my issue. Basically I'm trying to catch the error that occurs in my setter when updatesource is called and propagate it up to my the catch block shown below. The problem is if an exception occurs in the call stack below updatesource, BindingExpression.UpdateSource() seems to catch that error and handle it. I can't get the exception to make it back out to my catch statement. Can this behavior be disabled?

  BindingExpression be = textBox.GetBindingExpression(TextBox.TextProperty);

   try
   {
     be.UpdateSource();
   }
   catch (Exception ex)
   {
     MessageBox.Show("ex.Message");
   }

//////////////////////////////////////////////////////////////////

public string MyValue
{ get {return _value;}
  set {
        if(value > 10)
           throw new Exception("Out of Range"); 
      }
}

Is `ValidatesOnExceptions` set to `True` in your binding of the `Text` property? — Donut, Aug 10 '11 at 21:09
This setting seems to not have a bearing on whether an exception thrown in the call to `UpdateSource` gets propagated out to the surrounding try-catch block. — Seabass__, Aug 10 '11 at 21:52

Adam Jones · Accepted Answer · 2011-08-11T20:05:07.457

2

Binding in WPF and Silverlight can be configured to use exceptions thrown in the setter for validation. I believe Donut's comment about ValidatesOnExceptions is at the heart of the issue. The other related attribute (at least in Silverlight) is NotifyOnValidationError. If you aren't using this feature for validation you should be able to turn it off. If you are, you might be able to get it from from the validation system.

EDIT: I made a sample project to check out the situation, and while stepping through I found that UpdateSource() catches the exception for the purpose of the validation system, and it appears that it doesn't rethrow. You could create your own UpdateSource method (perhaps as an extension method with a different name) that updates the value of the property in the binding, but doesn't catch the exception (or catches and rethrows).

edited Aug 11 '11 at 20:05

answered Aug 10 '11 at 21:18

Adam Jones

711
3
9

As a side note, if you are trying to catch the error for the purpose of validation, you might consider just using the validation system since a lot of work is already done for you, and there is a consistent visual look & feel for validation errors in several of the built in controls. – Adam Jones Aug 10 '11 at 21:22
I agree when considering the code snippet given above. However I have a unique situation in the real code in which I would like to simply catch the exception that was thrown during the `UpdateSource()` call. For various reasons I'm trying an alternative to the built in validation [I'm not] using `IDataErrorInfo` and `ValidatesOnExceptions`. – Seabass__ Aug 10 '11 at 21:53
1

Updated my answer. I think for what you are trying to do you will need your own UpdateSource method. – Adam Jones Aug 12 '11 at 06:10

giryhepai · Answer 2 · 2019-05-23T10:52:39.327

I know this is a really old topic, but just stumbled upon it.

This article provides a really nice way of catching errors that occur inside the setters: https://wpf.2000things.com/2017/06/18/1211-catching-exceptions-originating-in-property-accessors/

How it works is extremely simple and effective: it creates an override of TraceListener and re-throws the exception inside the overriden WriteLine() method. Then, App.OnStartup() it adds the new Listener to PresentationTraceSources.DataBindingSource.Listeners and all of a sudden, the exception being thrown inside the setter can be caught.

The drawback is that if you have any binding errors throughout your application, these will be caught immediately and you'll start seeing them.

BindingExpression.UpdateSource swallows exception

2 Answers2