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Invalid attempt to call MetaData when reader is closed?

开发者 https://www.devze.com 2023-03-09 02:12 出处:网络
I\'m running an if else statement off of a datareader to query table d开发者_如何学编程ata and activate/de-activate some controls on a page. I implemented a using statement to automatically close the

I'm running an if else statement off of a datareader to query table d开发者_如何学编程ata and activate/de-activate some controls on a page. I implemented a using statement to automatically close the connection and the reader when I close the block, but I still get the reader is closed error on each of my if else statements. What's missing? Code below:

string comnt = "SELECT StatusId FROM Submission WHERE SubmissionId =" + x;


    using (SqlConnection editConn = new SqlConnection(connectionString))
    {
        editConn.Open();

        using (SqlCommand statCmd = new SqlCommand(comnt, editConn))
        {
            SqlDataReader dr = statCmd.ExecuteReader();
            dr.Read();
            if (dr.GetInt32(0) > 0)
            {
                PanelComment.Visible = true;
                PanelQuote.Visible = false;
                LnbFid.Visible = false;
                LnbCrim.Visible = false;
                LnbEo.Visible = false;
                LnbEpl.Visible = false;
                LnbNot.Visible = false;
                LnbPriv.Visible = false;
                LnbPub.Visible = false;

            }
            else
            {
                PanelComment.Visible = false;
            }

        } 


Try this way:

if (dr.HasRows)
{
     while (dr.Read())
     {
         if (dr.GetInt32(0) > 0)
         {
             ...
         }
     }
}

For more info, check this page:

Retrieving Data Using a DataReader


Your query is not getting any results back. Get used to the following construct if you are not sure if your query will return any data:

while (dr.Read()) //will return true while there is data to be read.
{
    ...
}


I faced this problem due to mismatch of reader name. i.e.

SqlCommand sqlmd = new SqlCommand();
SqlDataReader sqldr = sqlmd.ExecuteReader();
while (sqldr.Read())
{

    idd = (int)rdr["Id"];
}

later I replaced the code

 idd = (int)sqldr["Id"];

and the error was solved.


It seems the select statement returns no row and when you call dr.Read() for first time datareader will be closed imidiately for using data reader we always shows use if or while like what leniel said

   using (SqlCommand statCmd = new SqlCommand(comnt, editConn))
    {
        SqlDataReader dr = statCmd.ExecuteReader();
       if( dr.Read())
        if (dr.GetInt32(0) > 0)
        {
            PanelComment.Visible = true;
            PanelQuote.Visible = false;
            LnbFid.Visible = false;
            LnbCrim.Visible = false;
            LnbEo.Visible = false;
            LnbEpl.Visible = false;
            LnbNot.Visible = false;
            LnbPriv.Visible = false;
            LnbPub.Visible = false;

        }
        else
        {
            PanelComment.Visible = false;
        }

    }


if (conn.State == ConnectionState.Closed)
    conn.Open();

    SqlCommand qr1 = new SqlCommand("select TransID, FType, FldName, LTrans, 
        OnCCBeforeLoad, LTop, LLeft, LWidth, LHeight, LFColor 
        from jwOndropExecButtonS where active = 'T' and MyType = ''  
        and LTrans = '" + TmpRajTransID + "' order by dbo.val(TransID) ", conn);
    SqlDataReader d1 = qr1.ExecuteReader();
    while (d1.Read())
    {
        if (d1.HasRows)
        {
            string MrFldName = d1["FldName"].ToString().Trim();

            if (d1["OnCCBeforeLoad"].ToString().Trim() == "Clr")
                ClearValueandToolTipforFieldName(MrFldName);
            if (d1["LTop"].ToString().Trim() != "")
                DisplaySetTopValue(MrFldName, d1["LTop"].ToString().Trim());
            if (d1["LLeft"].ToString().Trim() != "")
                DisplaySetLeftValue(MrFldName, d1["LLeft"].ToString().Trim());
            if (d1["LWidth"].ToString().Trim() != "")
                DisplaySetWidthValue(MrFldName, d1["LWidth"].ToString().Trim());
            if (d1["LHeight"].ToString().Trim() != "")
                DisplaySetHeightValue(MrFldName, d1["LHeight"].ToString().Trim());
            if (d1["FType"].ToString().Trim() == "Visible")
                ShowTextBoxWithFldName(MrFldName);
            if (d1["FType"].ToString().Trim() == "InVisible")
                HideandClearTextBoxWithFldName(MrFldName);
            if (d1["FType"].ToString().Trim() == "InNVisible")
                HideOnlyTextBoxWithFldName(MrFldName);
            if (d1["FType"].ToString().Trim() == "Enable")
                SetEnableforFieldName(MrFldName);
            if (d1["FType"].ToString().Trim() == "Disable")
                SetDisableforFieldName(MrFldName);
        }
    }
    d1.Close();
    if (conn.State == ConnectionState.Open)
        conn.Close();

I got the same error once in a while at

if (d1["FType"].ToString().Trim() == "Visible") 

saying metadata not found. Later I found that the reader was not closed, but the ASP.NET program using too much memory closed the reader automatically. It mainly depends on the SQL server stage. If it is a regular error then please check your connection.

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