WPF how to manage ENTER hit on TextBox for messaging purpose

Question

Take a simple messaging program, such as Steam friend conversation.

When you hit ENTER, the message is sent, and the message field is emptied.

When you enter CTRL/SHIFT + ENTER a newline is created. If your cursor is not at the end of the input text, then all the text appearing after your cursor will be sent to a newline.

Well, how do you accomplish such a feat ?

Furthermore, I'd like to know how to have the aforementioned features and also how to still be able to paste a multiline text into the message field.

For now, this is my code. It's something but does not get all the job done :

private bool ctrlOrShift = false;
private void MessageField_KeyDown( object sender, KeyEventArgs e )
{
    if( e.Key == Key.LeftCtrl || e.Key == Key.LeftShift )
    {
        ctrlOrShift = true;
    }

    else if( e.Key == Key.Enter && ctrlOrShift != true && !MessageField.AcceptsReturn )
    {  
         AsyncSendMessage();
    }
    else if( e.Key == Key.Enter && ctrlOrShift != true && MessageField.AcceptsReturn )
    {
         MessageField.AcceptsReturn = false;
    }
    else if( e.Key == Key.Enter && ctrlOrShift == true )
    {
         ctrlOrShift = false;
         MessageField.AcceptsReturn = true;
         MessageField.Text += System.Environment.NewLine;
         MessageField.Select( MessageField.Text.Length, 0 );
         MessageField.AcceptsReturn = false;
    }
    else
    {
         ctrlOrShift = false; // Canceled because follow-up key wat not ENTER !
    }
}

The following scenarios occur :

1. Using CTR or SHIFT, I can create a new line in my TextBox :) ;
2. I cannot paste a multiline text from the Clipboard: only the first line will be pasted, nothing else :( ;
3. If I use CTRL + V to paste content, the MessageField_KeyDown event takes the CTRL hit is taken into account, therefore, if I press ENTER, message is not sent but a newline is created instead :/ (in a case where you would paste a content and send it right away) ;
4. If my cursor position is before the end of the input text, CTR/SHIT + ENTER will create a newline at the end of the text regardless of the cursor position :/

So, how can I tweak this code ? Thanks for the help !

Answer 1

The Result of the Solution is this:

Normal

After one SHIFT + ENTER

When you push ENTER it looks like in Normal only without text in the box

As mentioned in the comments you could use the AcceptsReturn and TextWrapping properties for a multiline textbox (like in steam). Use Height = Auto for a better looking one (otherwise you only have one line and all other lines disappear)
XAML
for Textbox:

<TextBox HorizontalAlignment="Left" Height="Auto" Margin="10,10,0,0" 
     TextWrapping="Wrap" Text="TextBox" VerticalAlignment="Top" 
     Width="497" AcceptsReturn="True" 
     KeyDown="TextBoxKeyDown" PreviewKeyDown="TextBoxPreviewKeyDown"/>

Event Handler:
This is not that easy as i thought first :'D But i figured it out.
When you use the AcceptsReturn Property the Enter Key is Handeled by the AcceptsReturn. So if you push enter you will see a new line instead of a Send() if you programm is like this:

private void TextBoxKeyDown(object sender, KeyEventArgs e)
{
    var textbox = sender as TextBox;
    // This will never happen because the Enter Key is handeled before
    // That means TextBoxKeyDown is not triggered for the Enter key
    if (e.Key == Key.Enter &&
        !(Keyboard.IsKeyDown(Key.LeftCtrl) || Keyboard.IsKeyDown(Key.RightCtrl)) &&
        !(Keyboard.IsKeyDown(Key.LeftShift) || Keyboard.IsKeyDown(Key.LeftShift)))
    {
        // Send(textBox.Text)
        textbox.Text = "";
    }
}

So you need to implement the PreviewKeyDown eventhandler. Because in the PreviewKeyDown event handler the Event is routed through the (Parent)Elements. Look at this Answer

Also note the e.Handled = true line. Otherwise the Enter is routed through the method to the AcceptsReturn and you will have 2 lines after the enter, but the Textbox is empty. With this method the KeyDown Method is no longer needed!

private void TextBoxPreviewKeyDown(object sender, KeyEventArgs e)
{
    // Enter key is routed and the PreviewKeyDown is also fired with the 
    // Enter key
    var textbox = sender as TextBox;
    // You don't want to clear the box when CTRL and/or SHIFT is down
    if (e.Key == Key.Enter && 
        !(Keyboard.IsKeyDown(Key.LeftCtrl) || Keyboard.IsKeyDown(Key.RightCtrl)) &&
        !(Keyboard.IsKeyDown(Key.LeftShift) || Keyboard.IsKeyDown(Key.RightShift)))
    {
        textbox.Text = "";
        e.Handled = true;
    }
}

The pros of the Multiline Textbox is that you can copy and paste + you have no problems with CTRL pushed or not.

What do you think about it?

Hope it helps