Execute code if file count in Database is greter than zero based on parameter value using C# in ASP.Net

Hi I want to place a server side validation on my file upload control.

I want user should not be able to submit the form unless a supporting document is uploaded on the database.

I have place this code on my from button submit before calling the save function.

I am checking count from the database table where i am storing documents and want to check if count is 0 then give java script alert.

Is this way is ok or is there any other way of validating this.

string ACount = GetDesc("select COUNT(Sno) as DocFound from test where RequestID ="+ RID +" and RequestStatus ='", "AAA");

if ACount = 0)
{
    ScriptManager.RegisterStartupScript(this.Page, this.GetType(), "tmp", "<script type='text/javascript'>alert(\"Please upload your supporting document.\");</script>", false);
    return;
}

Thanks