Silverlight中TextBox禁止输入和粘贴非数值字符

说明:Silverlight程序中有一个文本框控件TextBox名为textBox1，TextChanged事件处理函数如下，利用正则表达式禁止输入和粘贴非数值字符。

private string originStr = "";//存放符合要求的数值字符串
        private Regex regex = new Regex(@"^[+-]?(?!0\d)\d+(\.[0-9]+)?$");//数值字面量正则表达式
        private void textBox1_TextChanged(object sender,TextChangedEventArgs e)
        {
            string txtStr = textBox1.Text;
            if (string.IsNullOrEmpty(txtStr))
            {
                originStr = "";
                return;
            }
            if (txtStr.IndexOf('.') > 0 && txtStr.LastIndexOf('.') == txtStr.Length - 1 && txtStr.IndexOf('.') == txtStr.LastIndexOf('.'))
            {
                if (txtStr.IndexOf('-') == 0 && txtStr.IndexOf('.') == 1)
                {
                }
                else
                {
                    originStr = txtStr;
                    return;
                }
            }
            else if (txtStr.IndexOf('-') == 0 && txtStr.LastIndexOf('-') == 0 && txtStr.LastIndexOf('-') == txtStr.Length - 1)
            {
                originStr = txtStr;
                return;
            }
            else if (regex.IsMatch(txtStr))
                originStr = txtStr;
            else
            {
                textBox1.Text = originStr;
                if (!string.IsNullOrEmpty(txtStr))
                    textBox1.Select(originStr.Length,1);
            }
        }