Response.Redirect not working properly...

    protected void dgStudents_RowCommand(object sender, GridViewCommandEventArgs e)
    {
        int RIndex = Convert.ToInt32(e.CommandArgument);
        GridViewRow row = dgStudents.Rows[RIndex];
 
        string _studentid = row.Cells[0].Text;
        string _assignid = row.Cells[9].Text;
        string _userid = Master.UserID;
 
        if (e.CommandName == "AssignMe")
        {
            int cntAssign = Convert.ToInt32(SQLTasks.ExecuteScalar("SELECT dbo.fncStudentTaken('" + row.Cells[9].Text + "')"));
 
            if (cntAssign > 0)
            {
                Response.Redirect("~/Admin/Default.aspx?LocKey=" + _lockey + "&AlreadyTaken=yes");
            }
 
            SQLTasks.ExecuteNonQuery("UPDATE Assignments SET StaffAssignedto = '" + _userid + "', DateAssigned = GetDate() WHERE [id] = '" + _assignid + "'");
            Response.Redirect("~/Admin/Assign.aspx?id=" + _studentid + "&AssignmentID=" + _assignid + "&LocKey=" + _lockey);
        }
 
        if (e.CommandName == "NoShow")
        {
            string ip = (string)Request.ServerVariables["REMOTE_ADDR"];
            SQLTasks.ExecuteNonQuery("UPDATE Assignments SET LastActionIP = '" + ip + "', StaffAssignedto = '" + _userid + "', isNoShow = 1, isClosed = 1, DateClosed = GetDate() WHERE [id] = '" + _assignid + "'");
            Response.Redirect("~/Admin/Default.aspx?LocKey=" + _lockey);
        }
 
        if (e.CommandName == "TextPhone")
        {
            string SMSTo = row.Cells[10].Text + row.Cells[12].Text;
            SendSMS(SMSTo, row.Cells[7].Text);
            Response.Redirect("~/Admin/Default.aspx?LocKey=" + _lockey);
        }        
    }

                                              

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try
            {
                Response.Redirect("~/Admin/Assign.aspx?id=" + _studentid + "&AssignmentID=" + _assignid + "&LocKey=" + _lockey);
            }
            catch (System.Threading.ThreadAbortException ex)
            {
                Response.Write(ex.ToString());
            }
            catch (Exception ex)
            {
                Response.Write(ex.ToString());
            }

                                              

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protected void dgStudents_RowCommand(object sender, GridViewCommandEventArgs e)
    {
        int RIndex = Convert.ToInt32(e.CommandArgument);
        GridViewRow row = dgStudents.Rows[RIndex];
 
        string _studentid = row.Cells[0].Text;
        string _assignid = row.Cells[9].Text;
        string _userid = Master.UserID;
 
        if (e.CommandName == "AssignMe")
        {
            int cntAssign = Convert.ToInt32(SQLTasks.ExecuteScalar("SELECT dbo.fncStudentTaken('" + row.Cells[9].Text + "')"));
 
            if (Session["hackbln"] == null)
            {
                Session["hackbln"] = "false";
            }
 
            if (cntAssign > 0 && !bool.Parse(Session["hackbln"].ToString()))
            {
                Session["hackbln"] = "false";
            }
            else
            {
                Session["hackbln"] = "true";
                SQLTasks.ExecuteNonQuery("UPDATE Assignments SET StaffAssignedto = '" + _userid + "', DateAssigned = GetDate() WHERE [id] = '" + _assignid + "'");
                //Response.Redirect("~/Admin/Assign.aspx?id=" + _studentid + "&AssignmentID=" + _assignid + "&LocKey=" + _lockey);
            }
 
            if (bool.Parse(Session["hackbln"].ToString()))
            {
                Response.Redirect("~/Admin/Assign.aspx?id=" + _studentid + "&AssignmentID=" + _assignid + "&LocKey=" + _lockey);
            }
            else
            {
                Response.Redirect("~/Admin/Default.aspx?LocKey=" + _lockey + "&AlreadyTaken=yes");           
            }
        }
 
        if (e.CommandName == "NoShow")
        {
            string ip = (string)Request.ServerVariables["REMOTE_ADDR"];
            SQLTasks.ExecuteNonQuery("UPDATE Assignments SET LastActionIP = '" + ip + "', StaffAssignedto = '" + _userid + "', isNoShow = 1, isClosed = 1, DateClosed = GetDate() WHERE [id] = '" + _assignid + "'");
            Response.Redirect("~/Admin/Default.aspx?LocKey=" + _lockey);
        }
 
        if (e.CommandName == "TextPhone")
        {
            string SMSTo = row.Cells[10].Text + row.Cells[12].Text;
            SendSMS(SMSTo, row.Cells[7].Text);
            Response.Redirect("~/Admin/Default.aspx?LocKey=" + _lockey);
        }        
    }

                                              

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btnSave.Attributes.Add("onClick", "return confirm('This Student will be marked complete.  No other changes can be made after you save.  Continue?')");
        btnReturn.Attributes.Add("onClick", "return confirm('This will send the Student back to the Queue so another Representative can Assign them. Do you wish to continue?')");
        Response.ClearHeaders();
        Response.Clear();
        Response.AddHeader("cache-control", "no-cache");
        Response.AddHeader("Refresh", "");
        Session["hackbln"] = null;
 
        if (!IsPostBack)
        {
            string sql = "UPDATE Assignments SET StaffAssignedto = @AssignTo, DateAssigned = GetDate() WHERE [id] = @AssignId";
 
            Guid _uid = new Guid(Master.UserID);
            Guid _aid = new Guid(Request.QueryString["AssignmentId"].ToString());
 
            using (SqlConnection sqlconn = new SqlConnection(_conn))
            {
                SqlCommand cmd = new SqlCommand(sql, sqlconn);
                cmd.CommandType = CommandType.Text;
 
                cmd.Parameters.Add("@AssignTo", SqlDbType.UniqueIdentifier).Value = _uid;
                cmd.Parameters.Add("@AssignId", SqlDbType.UniqueIdentifier).Value = _aid;
 
                sqlconn.Open();
                cmd.ExecuteNonQuery();
            }
        }

                                              

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