Question

I have a service which continuously writes data in a separate thread into SQL database.Now from the same service if i am trying to read from the same table, since i already am writing into it,I get this exception : There is already an open DataReader associated with this Command which must be closed first.
So can anyone help me how to do this simultaneously?

Here s my code for reading data:

public Collection ReadData(string query)
{

        {

            _result = new Collection<string[]>();
            string[] tempResult;
            SqlDataReader _readerRead;
            using (_command = new SqlCommand(query, _readConnection))
            {
                _readerRead = _command.ExecuteReader();
                while (_readerRead.Read())
                {
                    tempResult = new string[4];
                    tempResult[0] = _reader[0].ToString();
                    tempResult[1] = _reader[1].ToString();
                    tempResult[2] = _reader[2].ToString();
                    tempResult[3] = _reader[3].ToString();
                    _result.Add(tempResult);
                    //Console.WriteLine("Name : {0} Type : {1} Value : {2} timestamp : {3}", _reader[0], _reader[1], _reader[2], _reader[3]);

                }
                if (_readerRead != null)
                {
                    _readerRead.Close();
                }
                _readConnection.Close();
                return _result;

            }
        }
    }

and here it is for writing to it :

public void WriteData(Collection<TagInfo> tagInfoList)
    {

        int i = 0;
        for (i = 0; i < tagInfoList.Count; i++)
        {
           using( _command = new SqlCommand(insert statement here)
            {
                _command.Parameters.AddWithValue("Name", tagInfoList[i].Name);
                _command.Parameters.AddWithValue("Type", tagInfoList[i].TagType);
                _command.Parameters.AddWithValue("Value", tagInfoList[i].Value);
                _reader = _command.ExecuteReader();
                if (_reader != null)
                {
                    _reader.Close();
                }
            }
        }

    }

Answer 1

Although its possible to do, using a separate connection I would question why you need to do this.

If you are reading and writing data to one table in the same service you will be placing unnecessary load on one SQL table, and depending on the number of queries you intend to make this could cause you problems. If you already have this data (in a different thread) why not Marshall the data from the background thread to where you need it as you write it into the database, and you don’t need to read the data anymore.

However…. it is difficult to give an fair answer without seeing the code/what you are looking to achieve.