Remove text after clicking in the textbox

Question

When you activate an application, a textbox with text \"hello\" will appear.

My question is:
When you click on the textbox in order to make input data, I want to rem

Answer 1

To expound upon Donut's answer so that your textbox will keep the text a user inputs unless it's purely whitespace, here's a solution that I use:

XAML

C#

void TextBox_GotFocus( object sender, RoutedEventArgs e )
{
    TextBox box = sender as TextBox;
    box.Text = string.Empty;
    box.Foreground = Brushes.Black;
    box.GotFocus -= TextBox_GotFocus;
}

void TextBox.LostFocus( object sender, RoutedEventArgs e )
{
    TextBox box = sender as TextBox;
    if( box.Text.Trim().Equals( string.Empty ) )
    {
        box.Text = "Search...";
        box.Foreground = Brushes.LightGray;
        box.GotFocus += TextBox_GotFocus;
    }
}