KeyDown事件:

private void TextBox_KeyDown(object sender, System.Windows.Input.KeyEventArgs e)
        {
            TextBox txt = sender as TextBox;

             //遮蔽非法按鍵
            if ((e.Key >= Key.NumPad0 && e.Key <= Key.NumPad9) || e.Key == Key.Decimal)
            {
                if (txt.Text.Contains(".") && e.Key == Key.Decimal)
                {
                    e.Handled = true;
                    return;
                }
                e.Handled = false;
            }
            else if (((e.Key >= Key.D0 && e.Key <= Key.D9) || e.Key == Key.OemPeriod) && e.KeyboardDevice.Modifiers != ModifierKeys.Shift)
            {
                if (txt.Text.Contains(".") && e.Key == Key.OemPeriod)
                {
                    e.Handled = true;
                    return;
                }
                e.Handled = false;
            }
            else
            {
                e.Handled = true;
            }
        }

TextChanged事件:

private void TextBox_TextChanged(object sender, TextChangedEventArgs e)
        {
            //遮蔽中文輸入和非法字元貼上輸入
            TextBox textBox = sender as TextBox;
            TextChange[] change = new TextChange[e.Changes.Count];
            e.Changes.CopyTo(change, 0);

            int offset = change[0].Offset;
            if (change[0].AddedLength > 0)
            {
                double num = 0;
                if (!Double.TryParse(textBox.Text, out num))
                {
                    textBox.Text = textBox.Text.Remove(offset, change[0].AddedLength);
                    textBox.Select(offset, 0);
                }
            }
        }