I have a working app that reads in a studentsID and the class that they recently finished. The app simply is an evaluation of the class. After they hit submit I take them to a different webpage. I do not want to allow them to go back to the previous (evaluation) page and resubmit. I also want to prevent that same student/class combo from being entered into the system.

I would appreciate any help on this subject.

Thanks

I think I have the logic to make it work. My problem is that the if statement is NEVER returning a null even when it should. Is my syntax wrong?

void Page_Load(object sender, EventArgs e) {

    if (!Page.IsPostBack) {


       string HeldKey = Request.QueryString["HeldKey"];
       string StudentID = Request.QueryString["StudentID"];
       Set_Name = Request.QueryString["Set_Name"];

       string SelectTest = "SELECT Smile_results.student_ID, smile_results.Held_Key FROM smile_results WHERE (smile_results.Student_ID = '"+StudentID+"' and smile_results.Held_Key = '"+HeldKey+"')";


         if (SelectTest == null)
            {
              SqlConnection myConnection = new SqlConnection(ConnectionString);
              SqlDataAdapter myCommand = new SqlDataAdapter(SelectCommand, myConnevtion);

              DataSet ds = new DataSet();
              myCommand.Fill(ds);

              DataGrid2.DataSource = ds;
              DataGrid2.DataBind();
                            }
           else Response.Redirect("http://elearning.diebold.com/testb/Sorry.htm");

                         }

I figured out that I was comparing the wrong things. You can't compare the strings you have to compare the dataAdapters. Unfortunatly I'm still getting thame results.
Here is my new code. I am comparing myTestcom and myTestcom2. Any ideas why they aren't being seen as equal by the if statement?

string SelectTest = "SELECT Smile_results.student_ID, smile_results.Held_Key FROM smile_results WHERE ((smile_results.Student_ID = '"+StudentID+"') and (smile_results.Held_Key = '"+HeldKey+"'))";

string SelectTest2 = "SELECT Smile_results.student_ID, smile_results.Held_Key FROM smile_results WHERE ((smile_results.Student_ID = null) and (smile_results.Held_Key = null))";

SqlConnection myConnection2 = new SqlConnection(ConnectionString);
SqlDataAdapter myCommand2 = new SqlDataAdapter(SelectCommand, myConnection2);
SqlDataAdapter myTestcom = new SqlDataAdapter(SelectTest, myConnection2);
SqlDataAdapter myTestcom2 = new SqlDataAdapter(SelectTest2, myConnection2);

if (myTestcom==myTestcom2)
 {

    DataSet ds = new DataSet();
    myCommand2.Fill(ds);

    DataGrid2.DataSource = ds;
    DataGrid2.DataBind();
 }