How do I move a text input by user in a textbox, into a textblock in C#?

Question

menuText is the textblock and commentTextbox is the textbox. I have cleared the textbox when text is inputted into the textbox. How do I make the text input in the textbox to appear in the textblock when the commentButton is clicked?

private void commentButton_Click(object sender, RoutedEventArgs e)
        {
            if (string.IsNullOrWhiteSpace(commentTextbox.Text))
            {

            }
            else
            {
                commentTextbox.Text = string.Empty;
                menuText.Text += commentTextbox.Text;
            }
        }

Answer 1

You are clearing the text box first, so, since commentTextbox.Text is an empty string, your last line is effectively doing menuText.Text += string.Empty;

You should invert the order of those calls, like that:

private void commentButton_Click(object sender, RoutedEventArgs e)
{
    if (String.IsNullOrWhiteSpace(commentTextbox.Text) == false)
    {
        menuText.Text += commentTextbox.Text;
        commentTextbox.Text = string.Empty;
    }
}