How to do a validation for empty grid view?

Hi,

I am working on VB.Net Framework 1.1.
I have a page with file upload, button upload and gridview.
When "Upload" button is clicked, i need to show the attachments in grid view.
If file is not attached, i need to show a error message.

In my code behind i wrote this code:
If dgTeam.Items.Count = 0 Then
DisplayPrompt("Please upload attachments")
End If

If ddlEvaluate.SelectedIndex = 0 Then
DisplayPrompt("Please select an evaluator")
End If

My issue is: if i didnt select evaluator and click submit button, the error message of file upload is display properly.
but if i select my evaluator and click submit button, i am not getting error message and my grid view is not validating as per my command.

Can u guys help me to resolve this issue. Either the above code or please suggest me to write validation in javascript.

Thanks.