wpf TextBox TexPreviewTextInput无法与绑定一起使用

Question

I'm trying to catch TexPreviewTextInput event from TextBox on binding change and it doesn't work. I want to be able to get the current value and the new value, I'm not changing some of the charterers, but the whole string with binding.

<TextBox x:Name="TB" Text="{Binding TBText}" PreviewTextInput="Sender_TexPreviewTextInput"/>

and the code behind is:

    public MainWindow()
    {
        InitializeComponent();
        TB.Text = "First Value";
        Loaded+=MainWindow_Loaded;
    }

    public string  TBText { get; set; }

    void MainWindow_Loaded(object sender, RoutedEventArgs e)
    {
        TB.Text = "Changed Value";
    }

    void Sender_TexPreviewTextInput(object sender, TextCompositionEventArgs e)
    {
        //Do Somthing
    }

Answer 1

PreviewTextInput event is raised whenever user input text via device (keyboard mostly).

If you are interested in whenever text changed from code behind or via binding or via device input, hook to TextChanged event.