Write data in database

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C#

PostgreSQL

I have written this function to write the data in database after reading the data from a file.
It stops working after " copyIn.Start ". I don't know whats the problem.
Any help will be great.

private void SaveAllByCopy(DateTime datetaken, string Weight, string lineno)
        {
           using (var connection = new NpgsqlConnection("Server=localhost ; port=5432; Database=testdb;Userid=postgres; Password=admin "))
                {
                    connection.Open();
                    using (var command = connection.CreateCommand())
                    { 
  command.CommandText = "COPY finaltest(datetaken,Weight,lineip) FROM STDIN";
  NpgsqlCopySerializer serializer = new NpgsqlCopySerializer(connection);
  NpgsqlCopyIn copyIn = new NpgsqlCopyIn(command, connection, serializer.ToStream);
                        try
                        {
                            copyIn.Start();
                                    foreach (var value in conairdata)
                                     {
                                        serializer.AddString(conairdata.datetaken);
                                         serializer.AddString(conairdata.Weight);
                                         serializer.AddDateTime(conairdata.lineno);
                                         serializer.EndRow();
                                         serializer.Flush();
                                     }
					 copyIn.End();
                                      serializer.Close();
                       }