Forcing binding update in TextBox

A typical usage of TextBox control in Silverlight is to bind it to a property and set the bind as two way. When the property changes, the TextBox is updated with the change and if the user changes the text in the TextBox, it is saved back to the property. Something like this:


<TextBox Text="{Binding Path=State, Mode=TwoWay}" />

A common problem developers face is when you have a TextBox control and a Submit button, which is enabled only when the data in TextBox is modified. The Submit button is not enabled until the LostFocus event of text box is fired. And LostFocus won’t be fired unless you click on something else. In this case, we can force the text to be updated. Register for TextChanged event and in this event handler, get the binding object and force an update.

 


<TextBox Text="{Binding Path=State, Mode=TwoWay}" TextChanged="textBox_TextChanged"/>

void textBox_TextChanged(object sender, TextChangedEventArgs e)
{

if(sender is TextBox)
{
TextBox tb = sender as TextBox;
BindingExpression binding = tb.GetBindingExpression(TextBox.TextProperty);
if (binding != null)
{
binding.UpdateSource();
}
}

}

Ta-da!

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