XAML Binding with Delay and KeyBinding

Question

I have this XAML code that works like a charm:

<TextBox Text="{Binding MyTextProperty, UpdateSourceTrigger=PropertyChanged}">
    <TextBox.InputBindings>
        <KeyBinding Command="{Binding MyOwnCommand}" CommandParameter="{Binding MyTextProperty}" Key="Enter" />
    </TextBox.InputBindings>
</TextBox>

There I have MyTextProperty that is passed as parameter to MyOwnCommand when I press enter key.

I do not want MyTextProperty updates every time I type a letter (because it has some logic asociated), but I do want it executes once I finish typing (without pressing enter key or losing the focus). The ideal solution would be this:

<TextBox Text="{Binding MyTextProperty, UpdateSourceTrigger=PropertyChanged, Delay=400}">
    <TextBox.InputBindings>
        <KeyBinding Command="{Binding MyOwnCommand}" CommandParameter="{Binding MyTextProperty}" Key="Enter" />
    </TextBox.InputBindings>
</TextBox>

The point here is the "Delay=400" parameter. It waits until I finish typing and then updates MyTextProperty.

But the problem I found at this point is that if I type something and immediately press enter, MyOwnCommand is called but MyTextProperty is not updated yet (it will be updated 400ms later).

I have tried to add the same delay in CommandParameter="{Binding MyTextProperty, Delay=400}", but it does not work.

What is the right approach to pass the CommandParameter once MyTextProperty has been updated?

Answer 1

TextBox.Text changes immediately after user types symbol from keyboard, even if there is a delay to send value to bound property. So you can bind CommandParameter to TextBox.Text directly:

<TextBox Name="MyTextBox" 
         Text="{Binding MyTextProperty, UpdateSourceTrigger=PropertyChanged, Delay=400}">
    <TextBox.InputBindings>
        <KeyBinding Command="{Binding MyOwnCommand}" 
                    CommandParameter="{Binding Text, ElementName=MyTextBox}" 
                    Key="Enter" />
    </TextBox.InputBindings>
</TextBox>