Question

Some days ago I realized that in Silverlight, in order to always update the bindings on any texbox (in order to validate for error in each KeyPress) I needed this code on TextChanged Event event in every TextBox I had in the system:

TextBox txCtl = (TextBox)sender; if (txCtl != null)
{
    var be = txCtl.GetBindingExpression(TextBox.TextProperty);

    if (be != null)
    {
        be.UpdateSource();
    }
}

This code works pretty well (source: http://forums.silverlight.net/t/51100.aspx/1). The problem is: I don’t want to repeat it in every view CodeBehind I have, so I decided to make a custom ViewBase where I would leave this code on it. What I did was simply:

public class ViewBase : ChildWindow
{
    protected void tboxTextChanged(object sender, TextChangedEventArgs e)
    {
        TextBox txCtl = (TextBox)sender; if (txCtl != null)
        {
            var be = txCtl.GetBindingExpression(TextBox.TextProperty);

            if (be != null)
            {
                be.UpdateSource();
            }
        }
    }
}

And then my view now is a ViewBase, instead of a UserControl, so I also changed the XAML to:

<src:ViewBase x:Class="Oi.SCPOBU.Silverlight.Pages.CadastroClassificacao"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"    
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:src="clr-namespace:Oi.SCPOBU.Silverlight.Pages" [...]

Finally, in my textbox I left the event referencing the same method as usual, but now the method is in ViewBase, istead of being in the CodeBehind:

<TextBox
   x:Name="tbxNome"
   Width="300"
   MaxLength="50"
   HorizontalAlignment="Left"
   TextChanged="tboxTextChanged"
   Text="{Binding DTOClassificacao.Nome, Mode=TwoWay, NotifyOnValidationError=True>

Seems pretty straightforward to me, but this doesn’t work. The code compiles, but in runtime I get the error: “Message=Failed to assign to property ‘System.Windows.Controls.TextBox.TextChanged’. [Line: 43 Position: 37]”, on the InitializeComponent() Method.

Anybody knows how can I assign a method from my base class to an event? Or will I really have to repeat this code in every single View I have?

Answer 1

in order to always update the bindings on any texbox (in order to
validate for error in each KeyPress) I needed this code on TextChanged
Event event in every TextBox I had in the system

Have you tried UpdateSourceTrigger.PropertyChanged?

<TextBox Text="{Binding Text, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>