<%@ Page Language="C#" %>

<script runat="server">

    protected void Button1_Click(Object sender, EventArgs e) {
         if (Page.IsValid) {
            Label1.Text = "PRAWIDŁOWY WPIS!";
         }
    }

    void ValidateNumber(object source, ServerValidateEventArgs args)
    {
       try 
       {
          int num = int.Parse(args.Value);
          args.IsValid = ((num%5) == 0);
       }
       catch(Exception ex)
       {
          args.IsValid = false;
       }
    }

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>CustomValidator</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <p>
            Number: 
            <asp:TextBox ID="TextBox1" 
             Runat="server"></asp:TextBox>
             &nbsp;
            <asp:CustomValidator ID="CustomValidator1" 
             Runat="server" ControlToValidate="TextBox1" 
             Text="Liczba musi być podzielna przez 5" 
             OnServerValidate="ValidateNumber"></asp:CustomValidator>
        </p>
        <p>
            <asp:Button ID="Button1" OnClick="Button1_Click" 
             Runat="server" Text="Przycisk"></asp:Button>
        </p>
        <p>
            <asp:Label ID="Label1" Runat="server"></asp:Label>
        </p>
    </div>
    </form>
</body>
</html>
