C#, Login Screen Problem;

Question

I want to make a Login Screen, and by using DevExpress I added a "TextBox" and a "PasswordBox" 

then I wrote this;

private void Button_Click_1(object sender, RoutedEventArgs e)

        {

            string ka1 = "John";

            string ka2 = "Roll";

            string ka3 = "Funs";

            string ka4 = "Clark";

            string pw1 = "wert";

            string pw2 = "tuna";

            string pw3 = "rasta";

            string pw4 = "packed";

            if ((TextBox1.Text == ka1) && (Password.PasswordBox == pw1))

         

            return;

        }

------------------------------------------------------------------------

But VS2012 says "TextBox1 does not exist in the current context"

How can i create a login WPF?

Thanks in advance