C# WPF how to use value of object sender to clear value in the input-box which has evoked the code

Question

I'm creating a WPF application with a few input-text-fields and input should be checked if it contains only numbers and comma ( = convert to double must be possible) and so I have written the following code

private void txtBarauslagen_PreviewKeyDown(object sender, KeyEventArgs e)
{
    if (e.Key == Key.Return || e.Key == Key.Tab)
    {
        string text = txtBarauslagen.Text;

        if (text != "") // nur wenn Feld nicht leer
        {
            try
            {
                double convtext = double.Parse(text);
                MessageBox.Show(convtext.ToString());
                // txtNotiz_int.Focus();
            }
            catch
            {
                MessageBox.Show("FALSCH - nicht nur Zahlen!");
                txtBarauslagen.Text = ""; 
                e.Handled = e.Key == Key.Tab;
            }
        }
    }
}

The line "e.Handled = e.Key == Key.Tab;" is necessary because I have code in "LostFocus" which should only be executed if "convert to double" is possible.

I'd like to know if it is possible to change the line "txtBarauslagen.Text = "";" so that it is possible to refactor the code so that I can use the same code for another input-text-field. I have tried already to change it to "text.Text" in the catch-statement but that is not possible (I do not really know why).

To put it in a nutshell: I'd like to know if it is possible to retrieve the value for instance "txtBarauslagen.Text" or the object "txtBarauslagen" ( = my input-text-field) from "object sender).

Answer 1

Since the sender is supposed to be the TextBox which raised that event, just cast it to TextBox and you can access its Text property.

TextBox tb = (TextBox)sender;

BTW, if I were you, I will use double.TryParse method instead.