如何限置“textbox”控件只能输入特定的数字与字符？
求教：现在限定了textbox控件只能输入0-9数字，如何增加还能输入一个字符“.”？

比如能输入“9.5”、“10.22”

代码如下：

C# code

private void textBox4_KeyDown(object sender, KeyEventArgs e)        {            nonNumberEntered = false;            if (e.KeyCode < Keys.D0 || e.KeyCode > Keys.D9 )            {                if (e.KeyCode < Keys.NumPad0 || e.KeyCode > Keys.NumPad9 )                {                    if (e.KeyCode != Keys.Back)                    {                        nonNumberEntered = true;                    }                }            }        }        private void textBox4_KeyPress(object sender, KeyPressEventArgs e)        {            if (nonNumberEntered == true)            {                e.Handled = true;            }        }

[解决办法]
try
{
double x = Convert.ToDouble(TextBox1.Text);
}
catch
{
MessageBox.Show("非法的数字！");
}
[解决办法]
增加等于 '.'的判断，或者用正则

C# code

private void textBox1_Validating(object sender, CancelEventArgs e) { const string pattern = @"^\d+\.?\d+$"; string content = ((TextBox)sender).Text; if (!(Regex.IsMatch(content, pattern))) { MessageBox.Show( "只能输入数字!"); e.Cancel = true; } else xxxxxxx}