Question

I have a gridview which is fed by a stored proc via standard n-tier structure that should trigger the emplty row object but it doesn’t. Instead I get an exception “The IListSource does not contain any data source”. If I run the query in SQL server Management Studion it returns an empty row.

I suspect the issue is with the transact-sql, I’m using a PIVOR consrtuct and since I’m not that familiar how it works, I think that causes the issue. It was borrowed it from this blog and was modified by my predecesor.

Does anyone has an idea what causes the issue? Here the code.

<asp:GridView ID="gvSystemRMRiskRpt" runat="server" AutoGenerateColumns="true"
   CellPadding="3" PageSize="25" BackColor="White" BorderColor="MidnightBlue"
   BorderStyle="Groove" BorderWidth="1px" CssClass="TextCompact" GridLines="Vertical"
   OnRowDataBound="gvSystemRMRiskRpt_OnDataBound" EmptyDataText="Your request has returned zero records" >                
    <RowStyle BackColor="#EEEEEE" ForeColor="Black" />
    <SelectedRowStyle BackColor="#008A8C" Font-Bold="True" ForeColor="White" />
    <PagerStyle BackColor="#999999" ForeColor="Black" HorizontalAlign="Center" />
    <HeaderStyle BackColor="#000084" Font-Bold="True" ForeColor="White" />
    <AlternatingRowStyle BackColor="Gainsboro" />
    <FooterStyle BackColor="#CCCCCC" ForeColor="Black" VerticalAlign="Top" />
</asp:GridView>

Code file:

    protected void btnSearch_Click(object sender, EventArgs e)
    {
        Guid site = new Guid(ddlSites.SelectedValue);
        int interval = Convert.ToInt16(ddlIntervals.SelectedValue);
        string[] startDate = tbStartDate.Text.Split('/');  // 01-2001
        string[] stopDate = tbEndDate.Text.Split('/');     // 12/2002

        gvSystemRMRiskRpt.DataSource = Data.ByMonthYear(connectionManager,site,startDate[1],stopDate[1],interval);
        gvSystemRMRiskRpt.DataBind();
     }

Data Layer:

 public static DataSet ByMonthYear(ConnectionManager connectionManager, Guid site, string startDate, string stopDate, int interval)
    {
        SqlCommand cmd = new SqlCommand();
        cmd.CommandText = "[dbo].[ByMonthYear_StoredProc]";
        cmd.CommandType = CommandType.StoredProcedure;
        cmd.Connection = connectionManager.GetSqlConnectionContext();
        cmd.Transaction = connectionManager.GetSqlTransactionContext();

        SqlParameter paramSiteGUID = new SqlParameter("@SiteGUID", SqlDbType.UniqueIdentifier);
        paramSiteGUID.Value = site;
        cmd.Parameters.Add(paramSiteGUID);

        SqlParameter paramStartDate = new SqlParameter("@StartDate", SqlDbType.VarChar);
        paramStartDate.Value = startDate;
        cmd.Parameters.Add(paramStartDate);

        SqlParameter paramStopDate = new SqlParameter("@StopDate", SqlDbType.VarChar);
        paramStopDate.Value = stopDate;
        cmd.Parameters.Add(paramStopDate);

        SqlParameter paramProcedureAction = new SqlParameter("@ProcedureAction", SqlDbType.Int);
        paramProcedureAction.Value = 0; // From Primary Key
        cmd.Parameters.Add(paramProcedureAction);

        SqlParameter paramInterval = new SqlParameter("@Interval", SqlDbType.Int);
        paramInterval.Value = interval;
        cmd.Parameters.Add(paramInterval);

        SqlDataAdapter sqlDA = new SqlDataAdapter(cmd);
        DataSet ds = new DataSet();
        sqlDA.Fill(ds);

        cmd.Dispose();
        cmd = null;

        return ds;
    }

and the actual stored proc:

alter PROCEDURE [dbo].[ByMonthYear_StoredProc]
@ProcedureAction int,
@SiteGUID uniqueidentifier = null,
@StartDate varchar(4),
@StopDate varchar(4),
@Interval int
AS

DECLARE @cols NVARCHAR(2000)
DECLARE @query NVARCHAR(4000)

IF (@ProcedureAction = 0) -- From 
BEGIN

    SET NOCOUNT ON
    SET TRANSACTION ISOLATION LEVEL READ COMMITTED

    IF (@Interval = 1) -- Montly
    BEGIN
        SELECT @cols = STUFF(( SELECT DISTINCT TOP 100 PERCENT '],[' + cast(MonthYear as varchar(10)) FROM vByMonthYear where SiteGUID = @SiteGuid 
        and [Year] BETWEEN '2005' AND '2010' ORDER BY '],[' + cast(MonthYear as varchar(10)) FOR XML PATH('') ), 1, 2, '')
         + ']' SET @query = N'SELECT EventType, ' + @cols +' FROM (SELECT MonthYear,EventType,Value,OrderBy FROM vRByMonthYear 
         where SiteGUID = ' + CHAR(39) + CONVERT(nvarchar(36), @SiteGuid) + CHAR(39) + ' and Year BETWEEN 2005 AND 2010) p 
         PIVOT ( Sum ([Value] ) FOR MonthYear IN ( '+ @cols +' ) ) AS pvt order by OrderBy' 
        execute(@query)
    END
END

Just to reiterate, if I run SELECT DISTINCT TOP 100 PERCENT ‘],[‘ + cast(MonthYear as varchar(10)) FROM vByMonthYear where SiteGUID = @SiteGuid and [Year] BETWEEN ‘2005’ AND ‘2010’ in the query window and I substitute the @SiteGuid with an actual value that I know has no record I get an empty row but in my app I get the exception.

Answer 1

I suspect this is what happened but am not 100% certain. The adapter

  SqlDataAdapter sqlDA = new SqlDataAdapter(cmd);
  DataSet ds = new DataSet();
  sqlDA.Fill(ds);

was being filled with a row of no data and so the dataset that was returned was not treated as empty – not sure why. I suspect the weird SQL Pivot was returning some reference or white space.

Anyway, I had changed the method to return a DataTable instead of DataSet and droped the entire SqlDataAdapter and instead used a SqlReader which worked. Probably saved some 1 milisecond of overhead in the process.

using (SqlDataReader _reader = cmd.ExecuteReader())
{
     DataTable dt = new DataTable();
     dt.Load(_reader);
     cmd.Dispose();
     return dt;
}