TextBox限制只能输入整数或小数

1. 在KeyDown事件中屏蔽非法按键。

private void TextBox_KeyDown(object sender, KeyEventArgs e)
{
    TextBox txt = sender as TextBox;
    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;
    }
}

2. 在TextChanged事件中利用TextChange类屏蔽非法输入和粘贴输入。　

private void TextBox_TextChanged(object sender, TextChangedEventArgs e)
{
    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);
        }
    }
}

TextChange类，是Framework 3.0SP1和3.5中新增的，3.0本身是没有的。

3. 在TextChanged事件中利用正则表达式屏蔽非法按键输入和粘贴输入。

private const string pattern_integer = @"^[0-9]*$";
private const string pattern_decimal = @"^[0-9]*[.]?[0-9]*$";

string strDoublebak; //记录TextBox原来的内容

private void txtDouble_TextChanged(object sender, TextChangedEventArgs e)
{
    Match m = Regex.Match(this.txtDouble.Text, pattern_decimal);   // 匹配正则表达式

    if (!m.Success) // 输入的不是小数
    {
        this.txtDouble.Text = strDoublebak;  // textBox内容不变

        // 将光标定位到文本框的最后
        this.txtDouble.SelectionStart = this.txtDouble.Text.Length;
    }
    else   // 输入的是小数
    {
        strDoublebak = this.txtDouble.Text;   // 将现在textBox的值保存下来
    }
}