OleDbCommand in Using block: COM object that has been separated from its underlying RCW cannot be used

Question

I got error "System.Runtime.InteropServices.InvalidComObjectException: 'COM object that has been separated from its underlying RCW cannot be used.'" ONLY when i execute OleDbCommand object in using block with parameters

using (OleDbCommand comm = new OleDbCommand())
        {
            comm.Connection = conn;
            comm.CommandType = CommandType.Text;
            string txt = "SELECT* FROM [ListForGroup] WHERE [email] = @email";
            comm.Parameters.Add("@email", OleDbType.VarWChar).Value = userEmail;
            comm.CommandText = txt;
            conn.Open();
            OleDbDataReader reader = comm.ExecuteReader();
            List<ListForGroups> list = returnLists(reader);
            conn.Close();
            cmbSelectList.DataSource = list;
            cmbSelectList.DisplayMember = "listName";
            cmbSelectList.ValueMember = "listForGroupsID";
        }

Does anyone know reason for that. I can resolve it to use OleDbCommand object with CommandText without parameters but i read that's bad idea. And i want to do it in using block to be sure that all reasources will be released.

Answer 1

I resolved this problem

using (OleDbConnection conn = new OleDbConnection(connString))
    {
        OleDbCommand comm = new OleDbCommand();
        comm.Connection = conn;
        comm.CommandType = CommandType.Text;
        string txt = "SELECT* FROM [ListForGroup] WHERE [email] = @email";
        comm.Parameters.Add("@email", OleDbType.VarWChar).Value = userEmail;
        comm.CommandText = txt;
        conn.Open();
        OleDbDataReader reader = comm.ExecuteReader();
        List<ListForGroups> list = returnLists(reader);

        cmbSelectList.DataSource = list;
        cmbSelectList.DisplayMember = "listName";
        cmbSelectList.ValueMember = "listForGroupsID";
    }

I don't know why I didn't create OleDbConnection in brackets next to using. Another when to resolve it is to close connection after using block.