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POHow to handle exception in Value converter so that custom error message can be displayed
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copied!<p>I have a textbox that is bound to a class with a property of type Timespan, and have written a value converter to convert a string into TimeSpan.</p> <p>If a non number is entered into the textbox, I would like a custom error message to be displayed (rather than the default 'input string is in the wrong format').</p> <p>The converter code is:</p> <pre><code> public object ConvertBack( object value, Type targetType, object parameter, CultureInfo culture) { try { int minutes = System.Convert.ToInt32(value); return new TimeSpan(0, minutes, 0); } catch { throw new FormatException("Please enter a number"); } } </code></pre> <p>I have set 'ValidatesOnExceptions=True' in the XAML binding.</p> <p>However, I have come across the following MSDN article, which explains why the above will not work:</p> <p>"The data binding engine does not catch exceptions that are thrown by a user-supplied converter. Any exception that is thrown by the Convert method, or any uncaught exceptions that are thrown by methods that the Convert method calls, are treated as run-time errors"</p> <p>I have read that 'ValidatesOnExceptions does catch exceptions in TypeConverters, so my specific questions are:</p> <ul> <li>When would you use a TypeConverter over a ValueConverter</li> <li>Assuming a TypeConverter isn't the answer to the issue above, how can I display my custom error message in the UI</li> </ul>

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