Telerik RadNumericUpDown for Silverlight does not update binding when value is blanked out

Note: This may be fixed in a later version of Telerik controls; this issue was discovered in the Telerik.Windows.Controls library; version 2011.1.315.1040

Working on a Silverlight application, we found ourselves with some dialogs that utilize the Telerik RadNumericUpDown control.  We discovered a defect when binding the Value property of the control to a ViewModel behind the scenes.

The original binding works as expected, and if the spinner controls are used to change the value, the ViewModel updates as we expect.  If a user types a new value into the control it also updated the binding on the ViewModel correctly.

The problem arises when we blank out the value by clicking into the textbox portion of the control, highlighting it and hitting the Backspace or Delete key.  Removing focus from the control or not, the ViewModel property bound to that control does not get updated.

To work around this, we created this Event Handler:

void RadNumericUpDown_ValueChanged(object sender, 
                                   RadRangeBaseValueChangedEventArgs e)
{
    if (sender is RadNumericUpDown)
    {
        RadNumericUpDown upDownControl = sender as RadNumericUpDown;
        if (!upDownControl.Value.HasValue)
            upDownControl.Value = upDownControl.Minimum;
    }
}

Now we apply this event handler to our XAML:

<telerik:RadNumericUpDown ValueChanged="RadNumericUpDown_ValueChanged" ... />

This makes the behavior act the same as if the user had used the down spinner on the control to modify the value down to the minimum.

This may not be the ideal solution for you, but understanding this will give you direction on how you can create your own workaround.  We started down the path of handling the KeyUp event, but ValueChanged seems much more appropriate.

Telerik makes fantastic controls; and I'm not mad by any means.  Being a developer myself, I realize these things happen; but I do hope they have handled this better in a later release.  And as far as I know this is the only control in the 2011.1.315.1040 version that has this issue.