Question

I need to validate a DropDownList in an ASP.NET project and am trying to use JavaScript even though I have never used it before.

I’m using the following ASP declaration and code JavaScript:

ASP declaration:

<asp:DropDownList ID="ddl1" runat="server" onprerender="ddl1_PreRender" ValidationGroup="AddNewCollection">
</asp:DropDownList>
<asp:CustomValidator ID="CustomValidator1" runat="server" ErrorMessage="Choose Type!"
ControlToValidate="ddl1"  ForeColor="Red" ValidationGroup="AddNewCollection" ClientValidationFunction="clientSideCheckValue"></asp:CustomValidator>>

JavaScript code:

 <script type="text/javascript">
    function clientSideCheckValue(source, args) 
     {
       var result1 = args.Value;   
       var rsult2 = document.getElementById("ddl1").value;
       if (result2 == null) {
          args.IsValid = false;
          return true;
       }
      args.IsValid = true;
    }
</script>

I have two questions about code mentioned above:

1.Why when I’m printing this row’s code var result1 = args.Value; intelisense dosen’t give me option to choose “Value” extension.

2.At this line of JavaScript code var rsult2 = document.getElementById(“ddl1”).value;

I get this error message Microsoft JScript runtime error: Object required.Have you got any idea why i meet this problem and how can i fix it?

Thank you in advance.

Answer 1

@Paul: “intelisense has no way of knowing what properties/methods args has, so it can’t give you the option.” Absolutely correct.

@Michael:

Assuming your JavaScript is in the .aspx markup, change your line to var rsult2 = document.getElementById(“<%=ddl1.ClientID” %>).value;. That will render the actual client ID of your DropDownList inside the script block.

Also, you appear to be just making sure an option has been picked. It’s a lot easier to add an <asp:RequiredFieldValidator /> and set the ControlToValidate property to “ddl1” if that’s all you want to do.

Hope this helps.