限制TextBox输入，只能输入整数

     public class TextBoxInt : TextBox
     {
         public TextBoxInt()
         {
             KeyDown += TextBoxInt_KeyDown;
             TextChanged += TextBoxInt_TextChanged;
         }

         private void TextBoxInt_TextChanged(object sender, TextChangedEventArgs e)
         {
             //屏蔽非法字符粘贴
             var textBox = sender as TextBox;
             if (textBox != null)
             {
                 var change = new TextChange[e.Changes.Count];
                 e.Changes.CopyTo(change, );

                 int offset = change[].Offset;
                 if (change[].AddedLength > )
                 {
                     int num;
                     if (!int.TryParse(textBox.Text, out num))
                     {
                         textBox.Text = textBox.Text.Remove(offset, change[].AddedLength);
                         textBox.Select(offset, );
                     }
                 }
             }
         }

         private void TextBoxInt_KeyDown(object sender, KeyEventArgs e)
         {
             if (e.Key >= Key.NumPad0 && e.Key <= Key.NumPad9)
             {
                 // 允许输入数字小键盘上的数字0-9
                 e.Handled = false;
             }
             else if ((e.Key >= Key.D0 && e.Key <= Key.D9) && e.KeyboardDevice.Modifiers != ModifierKeys.Shift)
             {
                 // 允许输入数字0-9，并且不能同时按着Shift键
                 e.Handled = false;
             }
             else if (e.Key == Key.Enter)
             {
                 // 允许输入回车
                 e.Handled = false;
             }
             else
             {
                 e.Handled = true;
             }
         }
     }