XAML - How can I use a KeyBinding command to go to a new line in the textbox?-CodePudding

I am simply trying to move to a new line when Return Shift are pressed.

I got this much from a previous post on here:

<TextBox.InputBindings>
                <KeyBinding Key="Return" Modifiers="Shift" Command=" " />
</TextBox.InputBindings>

But I cannot find anywhere that explains how to accomplish the move to a new line within the textbox.

I cannot use the: AcceptsReturn="True" as I want return to trigger a button.

CodePudding user response：

If you don't have an ICommand defined, you can attach a handler for the UIElement.PreviewKeyUp event to the TextBox. Otherwise you will have to define an ICommand implementation and assign it to the KeyBinding.Command so that the KeyBinding can actually execute. Either solution finally executes the same logic to add the linebreak.

You then use the TextBox.AppendText method to append a linebreak and the TextBox.CaretIndex property to move the caret to the end of the new line.

MainWindow.xaml

<Window>
  <TextBox PreviewKeyUp="TextBox_PreviewKeyUp" />
</Window>

MainWindow.xaml.cs

partial class MainWindow : Window
{
  private void TextBox_PreviewKeyUp(object sender, KeyEventArgs e)    
  {
    if (!e.Key.Equals(Key.Enter) 
      || !e.KeyboardDevice.Modifiers.HasFlag(ModifierKeys.Shift))
    {
      return;
    }

    var textBox = sender as TextBox;
    textBox.AppendText(Environment.NewLine);
    textBox.CaretIndex = textBox.Text.Length;
  }
}