Trying to use a session variable to export a gridview to Excel

Question

I have a report that is generated by passing a few variables via a SQL string. The problem is, when I try to export the resulting gridview to Excel, the gridview blanks itself out. I'm trying to use session variables to store the dataset but I don't understand them too well. Can someone help?

This is the code that runs on page load:

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            SqlConnection sqlconnectionStatus = new SqlConnection(str);
            string DDL_Value = Convert.ToString(Request.QueryString["DDL_Val"]);
            string Val_Value = Convert.ToString(Request.QueryString["Val_Val"]);
            string Trk_Value = Convert.ToString(Request.QueryString["Trk_Val"]);
            string Acct_Value = Convert.ToString(Request.QueryString["Acct_Val"]);
            //Use the ClassTesting class to determine if the dates are real, and fill in today's date if they're blank
            string StDt_Value = ClassTesting.checkFields(Request.Form["txtStartDate"], "Date");
            string EnDt_Value = ClassTesting.checkFields(Request.Form["txtEndDate"], "Date");

            //string StDt_Value = Convert.ToString(Request.QueryString["StDt_Val"]);
            //string EnDt_Value = Convert.ToString(Request.QueryString["EnDt_Val"]);



            string BTN_Value;
            // Because the date is stored as an INT, you have to request the string and then
            //   convert it to an INT
            string StDT_Vals = Request.QueryString["StDt_Val"].ToString();
            string EnDT_Vals = Request.QueryString["EnDt_Val"].ToString();



            string sqlquery;

            if (String.IsNullOrEmpty(Acct_Value))
            {
                if (String.IsNullOrEmpty(DDL_Value))
                {
                    BTN_Value = "2";
                }
                else
                {
                    BTN_Value = "1";
                }
            }
            else
            {
                BTN_Value = "3";
            }
            // Check to see if a specific Agent is being requested
            if (BTN_Value == "1")
            {
                // int StDT_Value = Convert.ToInt32(StDT_Vals);
                // int EnDT_Value = Convert.ToInt32(EnDT_Vals);

                sqlquery = "Select DISTINCT PL.PROC_NM as Agent_Name, CCM.UNIQUE_CLAIM_ID as Issue_Number, CCM.CLAIM_ID as Claim_Number, ";
                sqlquery = sqlquery + "CCM.SOCSEC as Employee_Last_Digit, CONVERT(VARCHAR(10), CCM.DATE_IMPORTED, 101) AS Import_Date, CONVERT(VARCHAR(10), CCM.Orig_Open_Date, 101) as Original_Review_Date, ";
                sqlquery = sqlquery + "AGL.ACCT_GRP as Account_Name, AL.ACCT_NUM as Account_Number, CCM.CDBBEN as Benefit_Option, BT1.StatusText as BenType1, ";
                sqlquery = sqlquery + "BT2.StatusText as BenType2, BT3.StatusText as BenType3, CCM.Cmplt as Review_Validated, CCM.Vldtn_Cmmnts as Validation_Comments, ";
                sqlquery = sqlquery + "CCM.Gtkpr_Cmmnts as Gatekeeper_Comments, TS.StatusText as Tracking_Status ";
                sqlquery = sqlquery + "from ClosedClaims_MERGE CCM ";
                sqlquery = sqlquery + "LEFT JOIN PROC_LIST PL ON CCM.Spare = PL.LOGIN ";
                sqlquery = sqlquery + "LEFT JOIN ACCT_LIST AL ON AL.ACCT_NUM = CCM.CDBACC ";
                sqlquery = sqlquery + "LEFT JOIN ACCT_GRP_LIST AGL ON AGL.ACCT_GRP_PK = AL.ACCT_GRP_FK ";
                sqlquery = sqlquery + "LEFT JOIN TrackingStatus TS ON TS.StatusCode = CCM.TrackingStatus ";
                sqlquery = sqlquery + "LEFT JOIN BenefitType_v3 BT1 ON BT1.StatusCode = CCM.BENEFIT_TYPE1 ";
                sqlquery = sqlquery + "LEFT JOIN BenefitType_v3 BT2 ON BT2.StatusCode = CCM.BENEFIT_TYPE2 ";
                sqlquery = sqlquery + "LEFT JOIN BenefitType_v3 BT3 ON BT3.StatusCode = CCM.BENEFIT_TYPE3  ";
                sqlquery = sqlquery + "WHERE CCM.Spare " + (DDL_Value == "" ? "IS NULL" : "LIKE '" + DDL_Value + "'") + " AND CCM.Cmplt " + (Val_Value == "" ? "IS NULL" : "LIKE '" + Val_Value + "'") + " AND CCM.TrackingStatus IN (" + Trk_Value + ") AND CCM.SpareFinished >= '" + StDt_Value + "' AND CCM.SpareFinished <= '" + EnDt_Value + "'";
            }
            else
            {
                if (BTN_Value == "2")
                {
                    sqlquery = "Select DISTINCT PL.PROC_NM as Agent_Name, CCM.UNIQUE_CLAIM_ID as Issue_Number, CCM.CLAIM_ID as Claim_Number, ";
                    sqlquery = sqlquery + "CCM.SOCSEC as Employee_Last_Digit, CONVERT(VARCHAR(10), CCM.DATE_IMPORTED, 101) AS Import_Date, CONVERT(VARCHAR(10), CCM.Orig_Open_Date, 101) AS Original_Review_Date, ";
                    sqlquery = sqlquery + "AGL.ACCT_GRP as Account_Name, AL.ACCT_NUM as Account_Number, CCM.CDBBEN as Benefit_Option, BT1.StatusText as BenType1, ";
                    sqlquery = sqlquery + "BT2.StatusText as BenType2, BT3.StatusText as BenType3, CCM.Cmplt as Review_Validated, CCM.Vldtn_Cmmnts as Validation_Comments, ";
                    sqlquery = sqlquery + "CCM.Gtkpr_Cmmnts as Gatekeeper_Comments, TS.StatusText as Tracking_Status ";
                    sqlquery = sqlquery + "from ClosedClaims_MERGE CCM ";
                    sqlquery = sqlquery + "LEFT JOIN PROC_LIST PL ON CCM.Spare = PL.LOGIN ";
                    sqlquery = sqlquery + "LEFT JOIN ACCT_LIST AL ON AL.ACCT_NUM = CCM.CDBACC ";
                    sqlquery = sqlquery + "LEFT JOIN ACCT_GRP_LIST AGL ON AGL.ACCT_GRP_PK = AL.ACCT_GRP_FK ";
                    sqlquery = sqlquery + "LEFT JOIN TrackingStatus TS ON TS.StatusCode = CCM.TrackingStatus ";
                    sqlquery = sqlquery + "LEFT JOIN BenefitType_v3 BT1 ON BT1.StatusCode = CCM.BENEFIT_TYPE1 ";
                    sqlquery = sqlquery + "LEFT JOIN BenefitType_v3 BT2 ON BT2.StatusCode = CCM.BENEFIT_TYPE2 ";
                    sqlquery = sqlquery + "LEFT JOIN BenefitType_v3 BT3 ON BT3.StatusCode = CCM.BENEFIT_TYPE3  ";
                    sqlquery = sqlquery + "WHERE CCM.Cmplt " + (Val_Value == "" ? "IS NULL" : "LIKE '" + Val_Value + "'") + " AND CCM.TrackingStatus IN (" + Trk_Value + ") AND CCM.SpareFinished >= '" + StDt_Value + "' AND CCM.SpareFinished <= '" + EnDt_Value + "'";
                }
                else
                {
                    sqlquery = "Select DISTINCT PL.PROC_NM as Agent_Name, CCM.UNIQUE_CLAIM_ID as Issue_Number, CCM.CLAIM_ID as Claim_Number, ";
                    sqlquery = sqlquery + "CCM.SOCSEC as Employee_Last_Digit, CONVERT(VARCHAR(10), CCM.DATE_IMPORTED, 101) AS Import_Date, CONVERT(VARCHAR(10), CCM.Orig_Open_Date, 101) AS Original_Review_Date, ";
                    sqlquery = sqlquery + "AGL.ACCT_GRP as Account_Name, AL.ACCT_NUM as Account_Number, CCM.CDBBEN as Benefit_Option, BT1.StatusText as BenType1, ";
                    sqlquery = sqlquery + "BT2.StatusText as BenType2, BT3.StatusText as BenType3, CCM.Cmplt as Review_Validated, CCM.Vldtn_Cmmnts as Validation_Comments, ";
                    sqlquery = sqlquery + "CCM.Gtkpr_Cmmnts as Gatekeeper_Comments, TS.StatusText as Tracking_Status ";
                    sqlquery = sqlquery + "from ClosedClaims_MERGE CCM ";
                    sqlquery = sqlquery + "LEFT JOIN PROC_LIST PL ON CCM.Spare = PL.LOGIN ";
                    sqlquery = sqlquery + "LEFT JOIN ACCT_LIST AL ON AL.ACCT_NUM = CCM.CDBACC ";
                    sqlquery = sqlquery + "LEFT JOIN ACCT_GRP_LIST AGL ON AGL.ACCT_GRP_PK = AL.ACCT_GRP_FK ";
                    sqlquery = sqlquery + "LEFT JOIN TrackingStatus TS ON TS.StatusCode = CCM.TrackingStatus ";
                    sqlquery = sqlquery + "LEFT JOIN BenefitType_v3 BT1 ON BT1.StatusCode = CCM.BENEFIT_TYPE1 ";
                    sqlquery = sqlquery + "LEFT JOIN BenefitType_v3 BT2 ON BT2.StatusCode = CCM.BENEFIT_TYPE2 ";
                    sqlquery = sqlquery + "LEFT JOIN BenefitType_v3 BT3 ON BT3.StatusCode = CCM.BENEFIT_TYPE3  ";
                    sqlquery = sqlquery + "WHERE AL.ACCT_GRP_FK " + (Acct_Value == "" ? "IS NULL" : "LIKE '" + Acct_Value + "'") + " AND CCM.Cmplt " + (Val_Value == "" ? "IS NULL" : "LIKE '" + Val_Value + "'") + " AND CCM.TrackingStatus IN (" + Trk_Value + ") AND CCM.SpareFinished >= '" + StDt_Value + "' AND CCM.SpareFinished <= '" + EnDt_Value + "'";
                }
            }

            SqlConnection con = new SqlConnection(str);
            SqlCommand cmd = new SqlCommand(sqlquery, con);
            SqlDataAdapter adapter = new SqlDataAdapter(cmd);

            // Fill the DataSet.
            DataSet ds = new DataSet();
            adapter.Fill(ds, "dailyview");

            // Store the dataset in a session variable
            Session["SSQualOfSub"] = ds;

            // Perform the binding.
            GVQualOfSub.DataSource = ds;
            GVQualOfSub.DataBind();
        }

    }

And here is the code I'm using to export:

    private void ExportGridView()
    {
        // Exports the data in the GridView to Excel
        // First call the session variable to refill the gridview
        DataTable gridDataSource = (DataTable)Session["SSQualOfSub"];

        GVQualOfSub.Visible = true;
        GVQualOfSub.DataSource = gridDataSource;
        GVQualOfSub.DataBind();

        string attachment = "attachment; filename=Qual_Of_Subs.xls";
        Response.ClearContent();
        Response.AddHeader("content-disposition", attachment);
        Response.ContentType = "application/ms-excel";
        StringWriter sw = new StringWriter();
        HtmlTextWriter htw = new HtmlTextWriter(sw);
        GVQualOfSub.RenderControl(htw);
        Response.Write(sw.ToString());
        Response.End();

    }

I'm getting an error when I try to export.

Unable to cast object of type 'System.Data.DataSet' to type 'System.Data.DataTable'.

My apologies, I'm somewhat new to C#. Any help is appreciated.

Answer 1

You are storing a DataSet in Session and later you are trying to access it as DataTable.

You should do:

DataSet gridDataSource = (DataSet)Session["SSQualOfSub"];

instead of

DataTable gridDataSource = (DataTable)Session["SSQualOfSub"];

I am not sure about your particular scenario, but usually it is not a good idea to store large amount of data in Session, as it is maintained per user on the server.

Apart from the current error, you should use SqlParameter with your SqlCommand, you are concatenating queries and prone to SQL Injection