实现效果:

知识运用:

实现代码:
private void button1_Click(object sender, EventArgs e)
{
if (IsValidate(textBox1.Text.ToString()))
label1.Text = "输入正确";
else
label1.Text = "请输入数字";
}
public bool IsValidate(string str_number) {
return System.Text.RegularExpressions.
Regex.IsMatch(str_number,@"^[0-9]*$");
}