For iLoop = 2 to iSqrt
　　If iPrime mod iLoop = 0 then
　　args.IsValid = False
　　Exit Sub
　　End If
　　Next

　　args.IsValid = True
　　End Sub
　　</script>

　　<form method="post" runat="server">
　　Enter your favorite prime number:
　　<asp:textbox id="txtPrimeNumber" runat="server" />

　　<%-- Create the CustomValidator control --%>
　　<asp:CustomValidator runat="server" id="custPrimeCheck"
　　ControlToValidate="txtPrimeNumber"
　　OnServerValidate="PrimeNumberCheck"
　　ErrorMessage="Invalid Prime Number" />

　　<%-- Create two CompareValidator controls: the first ensures that
　　the number entered by the user is an Integer; the second
　　makes sure it is positive. --%>
　　<asp:CompareValidator runat="server" id="compPrimeNumber"
　　Operator="DataTypeCheck" Type="Integer"
　　Display="Dynamic" ControlToValidate="txtPrimeNumber"
　　ErrorMessage = "You must enter an integer value." />
　　<asp:CompareValidator runat="server" id="compPrimeNumberPositive"
　　Operator="GreaterThan" Type="Integer"
　　Display="Dynamic" ValueToCompare="0"
　　ControlToValidate="txtPrimeNumber"
　　ErrorMessage = "You must enter a value greater than zero." />

　　<p><asp:button id="btnSubmit" runat="server"
　　OnClick="btnSubmit_Click" Text="Submit" />
　　</form>