Making a TextBox values all upper-case or lower-case characters in WPF

public enum CharacterCasing
{  
  Normal = 0,
  Upper = 1,
  Lower = 2,
}

//For Upper case letter:- 
textBox1.CharacterCasing = CharacterCasing.Upper;  

//For Lower case letter:- 
textBox2.CharacterCasing = CharacterCasing.Lower;