Coerce a WPF TextBox not working anymore in .NET 4.0

Question

In my WPF application I have a TextBox where the user can enter a percentage (as int, between 1 and 100). The Text property is databound to a property in a ViewModel, where

Answer 1

Try using in xaml Explicit instead of PropertyChanged:

<TextBox Text="{Binding Percentage, Mode=TwoWay, UpdateSourceTrigger=Explicit, TargetNullValue={x:Static System:String.Empty}}"
             TextChanged="TextBox_TextChanged" />

and in code behind UpdateSource instead of UpdateTarget

private void TextBox_TextChanged(object sender, TextChangedEventArgs e)
    {
        // Removed safe casts and null checks
        ((TextBox)sender).GetBindingExpression(TextBox.TextProperty).UpdateSource();
    }

Tested it and it works. Btw this problem will probably be resolved in a later version of .NET.

Answer 2

You can use PropertyChanged. However, try binding to the EditValueProperty dependency instead of the TextProperty dependency (or events). It will work as desired.