function return the DbDataReader with passing database connection and sql query

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Hi ,
I have written function for getting the datareader using connection and query but some time is gives error , "{System.InvalidOperationException: There is already an open DataReader associated with this Command which must be closed first."
Please help for this
Thanks
vilas

C#

public static DbDataReader GetDataReader(DbConnection myConnection, string strQry)
        {
            DbDataReader ObjmyReader0 = null;
            DbDataReader ObjmyReader = null;


            string RetVal = string.Empty;
            DbCommand myCommand = null;
             myCommand = (DbCommand)myConnection.CreateCommand();
            // myCommand.CommandText = "SELECT * FROM Dept";
            myCommand.CommandText = strQry;
            if (myConnection.State == ConnectionState.Closed || myConnection.State == ConnectionState.Broken) {
                myConnection.Open();
            }

            try
            {
                if (ObjmyReader != null)
                {
                    ObjmyReader.Close();
                }

                ObjmyReader = myCommand.ExecuteReader(System.Data.CommandBehavior.CloseConnection);
            }
            catch (Exception rdExc)
            {
                if ((ObjmyReader != null) && (ObjmyReader.IsClosed == false))
                {
                    ObjmyReader.Close();
                    ObjmyReader = myCommand.ExecuteReader();
                }
            }
            finally
            {
                myCommand.Dispose();
                ObjmyReader0 = ObjmyReader;
               
               // ObjmyReader.Close();
            }

            return ObjmyReader0;
           
        }

Posted 7-Dec-12 0:01am

Mogya

Updated 7-Dec-12 23:22pm

v3

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Comments

choudhary.sumit 7-Dec-12 6:10am

close your reader at the very top line in GetDataReader(..) method.

Mogya 7-Dec-12 7:30am

ok thanks ,
i have tried to close reader first before calling getdatareader method ,
But at the time of dynamic calling i.e in while loop it is fail

Jibesh 7-Dec-12 20:13pm

The above code close the connection only when ObjmyReader != null which never gets executed because its always null and gets assigned after this line.

do check the ConnectionState.Opened means close the connection opened by the reader. or close the Reader itself with last readerObject not with the newly created one.

Tadit Dash (ତଡିତ୍ କୁମାର ଦାଶ) 8-Dec-12 1:07am

You have not closed the connection myConnection.
In finally block, write like myConnection.Close();.

thursunamy 8-Dec-12 5:34am

Hi,
Write to your connection string MultipleActiveResultSets=true

Menon Santosh 8-Dec-12 5:37am

write the following code in finally block
if (ObjmyReader0 != null)
{
if (!ObjmyReader0.IsClosed)
{
ObjmyReader0.Close();
}
}

Mogya 10-Dec-12 1:53am

thanks this is ok.

2 solutions

Solution 2

I have use dataTable and load the Idatareader and after this create the datareader ,

there after i am easily used this function with multiple loop.

C#

public static IDataReader GetDataReader(DbConnection myConnection, string strQry)
        {
            IDataReader ObjmyReader0 = null;
            IDataReader ObjmyReader = null;

            var dt = new DataTable();

            string RetVal = string.Empty;
            DbCommand myCommand = null;
             myCommand = (DbCommand)myConnection.CreateCommand();
            // myCommand.CommandText = "SELECT * FROM Dept";
            myCommand.CommandText = strQry;
            if (myConnection.State == ConnectionState.Closed || myConnection.State == ConnectionState.Broken) {
                myConnection.Open();
            }

            try
            {
                if (ObjmyReader != null)
                {
                    if (ObjmyReader.IsClosed == false) 
                    {
                        ObjmyReader.Close();
                    }
                }

                ObjmyReader = (IDataReader)myCommand.ExecuteReader(System.Data.CommandBehavior.CloseConnection);
                //var dt = new DataTable();
                dt.Load(ObjmyReader);
               // dt.CreateDataReader();
               // return dt.CreateDataReader();

              
            }
            catch (Exception rdExc)
            {
                if ((ObjmyReader != null) && (ObjmyReader.IsClosed == false))
                {
                    ObjmyReader.Close();
                    ObjmyReader = (IDataReader)myCommand.ExecuteReader();
                }
            }
            finally
            {
                myCommand.Dispose();
                ObjmyReader0 = ObjmyReader;
               
               // ObjmyReader.Close();
            }

            //return ObjmyReader0;
            return dt.CreateDataReader();
            //return (IDataReader)Convert.ChangeType(ObjmyReader0, typeof(IDataReader));
            ObjmyReader0.Dispose();
        }

Posted 17-Jan-13 1:16am

Mogya

Updated 17-Jan-13 17:44pm

v2

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D Waller · Accepted Answer · 2012-12-08T01:01:00

Try the following implementation (I have not tested this):

C#

public void TestGetDataReader()
        {
            string strDbConn = "Database connection string";
            string strQry = "Database Query";

            using (DbConnection dbConn = new SqlConnection(strDbConn))
            {
                dbConn.Open();
                using (DbDataReader dr = GetDataReader(dbConn, strQry))
                {
                    // Use results from data reader here
                    // using will automatically close the data reader once you have finished with the results
                }
            }
        }

        public static DbDataReader GetDataReader(DbConnection myConnection, string strQry)
        {
            using (DbCommand cmd = (DbCommand)myConnection.CreateCommand())
            {
                cmd.CommandText = strQry;

                if (myConnection.State == ConnectionState.Closed || myConnection.State == ConnectionState.Broken)
                {
                    myConnection.Open();
                }

                return cmd.ExecuteReader();
            }
        }