垃圾,给你们一个比较全的.
private bool panduan(string a)
{
return Regex.IsMatch(a, @"^\d*[.]?\d*$");

}
private void textBox4_Validating(object sender, CancelEventArgs e)
{
button1.Enabled = true;
bool a = panduan(textBox4.Text.Trim());
if (a == false || textBox4.Text==string.Empty)
{
e.Cancel = true;
errorProvider1.SetError(textBox4, "价格只能为数字,且不能为空，请正确输入");
}
else
{
e.Cancel = false;
errorProvider1.SetError(textBox4, "");

}
}