C sharp - seleccionar ítem de combobox y mostrar un valor en textbox

private void ComboBox1_SelectedIndexChanged (object sender, EventArgs e)

{

    string textboxValue = string.Empty;

    switch (this.ComboBox1.SelectedItem.ToString())

    {

         case "administrativo" :

             textboxValue = "50000";

             break;

         case "item 2" :

             textboxValue = "valor 2";

             break;

         case "item 3" :

             textboxValue = "valor 3";

             break;

         case "item 4" :

             textboxValue = "valor 4";

             break;

         case "item 5" :

             textboxValue = "valor 5";

             break;

    }

    this.TextBox1.Text = textboxValue;

}