<script language="vb" runat="server">
Sub btnSubmit_Click(sender as Object, e as EventArgs)
If Page.IsValid then
Response.Write("<font color=""red""><i>" & txtPrimeNumber.Text & _
" is, indeed, a good prime number.</i></font>")
Else
Response.Write("<font color=""red""><i>" & txtPrimeNumber.Text & _
" is <b>not</b> a prime number.</i></font>")
End If
End Sub
Sub PrimeNumberCheck(sender as Object, args as ServerValidateEventArgs)
Dim iPrime as Integer = Cint(args.Value), iLoop as Integer, _
iSqrt as Integer = CInt(Math.Sqrt(iPrime)) 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>
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