Error while using data reader..

Rajavel G

9y873Learn iOS Programming

there is already an open datareader associated with this command-error

fn1:

SQL = "query"

reader = cmd.ExecuteReader()

If reader.Read() Then

' operation

reader.close()

end if

reader.close

fn:2

SQL = "query"

reader = cmd.ExecuteReader()

If reader.Read() Then

' operation

reader.close()

end if

reader.close

6 Replies

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Nitin Sontakke9y ago
If this is not resolved, please share the code in execComDB method. Looks like something wrong there.

In general, can you just check if you are creating a new command object every time. Because that's what the error says.
Rajavel G9y ago
Form1
SQL = "select Student_image from Student_personal_schooling where Student_rollno='" & lblregno.Text & "'"
execComDB(SQL)
reader = cmd.ExecuteReader()
While (reader.Read())
Dim byteBLOBData As [Byte]() = New [Byte](-1) {}
byteBLOBData = DirectCast(DirectCast(reader("Student_image"), Byte()), [Byte]())
Dim ms As New System.IO.MemoryStream(byteBLOBData)
pictureBox1.Image = System.Drawing.Image.FromStream(ms)
' reader.Close()
End While
reader.Close()
Form2:
SQL = "SELECT Student_curntstd,Student_curntschl,Student_curntcity,Student_curnttaluk,Student_curntdistrct,Student_std1,Student_schl1,Student_city1,Student_taluk1,Student_district1,Student_std2,Student_schl2,Student_city2,Student_taluk2,Student_district2,Student_std3,Student_schl3,Student_city3,Student_taluk3,Student_district3,Student_std4,Student_schl4,Student_city4,Student_taluk4,Student_distrct4,Student_std5,Student_schl5,Student_city5,Student_taluk5,Student_distrct5,Student_std6,Student_schl6,Student_city6,Student_taluk6,Student_district6,Student_std7,Student_schl7,Student_city7,Student_taluk7,Student_distrct7,Student_std8,Student_schl8,Student_city8,Student_taluk8,Student_district8,Student_std9,Student_schl9,Student_city9,Student_taluk9,Student_district9,Student_std10,Student_schl10,Student_city10,Student_taluk10,Student_district10,Student_std11,Student_schl11,Student_city11,Student_talik11,Student_district11 FROM Student_school where Student_rollno= '" & Student_update_home.rollno & "' "
execComDB(SQL)
reader = cmd.ExecuteReader()
'cmd.CommandText = "SELECT curntstd,curntschl,curntcity,curnttaluk,curntdistrct,std1,schl1,city1,taluk1,district1,std2,schl2,city2,taluk2,district2,std3,schl3,city3,taluk3,district3,std4,schl4,city4,taluk4,distrct4,std5,schl5,city5,taluk5,distrct5,std6,schl6,city6,taluk6,district6,std7,schl7,city7,taluk7,distrct7,std8,schl8,city8,taluk8,district8,std9,schl9,city9,taluk9,district9,std10,schl10,city10,taluk10,district10,std11,schl11,city11,talik11,district11 FROM tblschlhistory where rollno='" + no + "'"
While (reader.Read())
txtcurntstd.Text = reader("Student_curntstd").ToString()

End While
reader.Close()
Rajavel G9y ago
There is already an open DataReader associated with this Command which must be closed first.
Nitin Sontakke9y ago
First, try using using clause, if possible, so that reader will be closed and discarded.

Another thing is why there is reader.Close() write twice? It should be only once.

Another thing is the ExecuteReader method has a CommandBehaviour parameter, set it to CloseConnection.

Let us know if it resolves the issue. Please post the real code and full error.
Rajavel G9y ago
i am using a reade in multiple form so below code is not working.. displaying same eroor..
Manas Mohapatra9y ago
If you want to execute multiple SQL statements then you can use NextResult() , follow below link:

http://vb.net-informations.com/ado.net-dataproviders/ado.net-multiple-result-sets.htm

OR you can try like below:
using (var myConnection = null)
{
  //myConnection.Open();

  var cmd = new MySqlCommand("SELECT * FROM table1", myConnection))
  using (var myDataReader = cmd.ExecuteReader())
  {
    while(myDataReader.Read())
    {
      //Perform work.
    }
  } // Reader will be Disposed/Closed here

  cmd.commandText = "SELECT * FROM table2";
  using (var reader = cmd.ExecuteReader())
  {
    while(reader.Read())
    {
      //Perform more work
    }
  } // Reader will be Disposed/Closed here
}