private bool IsNumeric(string str)
{
if (str == null || str.Length == 0) return false;

System.Text.ASCIIEncoding ascii = new System.Text.ASCIIEncoding();

byte[] bytestr = ascii.GetBytes(str);

foreach (byte c in bytestr)
{

if (c < 48 || c > 57)

{ return false; }

}

return true;

}

直接在客戶端用javascript不就可以了嗎
if (document.getElementById("ctl00_ContentPlaceHolder1_TextBox3").value.length <=0)
{
alert ('Basescore Is Null')
return false;
}
else
{
var snumber = Number(document.getElementById("ctl00_ContentPlaceHolder1_TextBox3").value);
if(isNaN(snumber))
{
alert("basescore must be number");
return false;
}
}

前面有 好多方 法。