Datatype mismatch issue in a Parametrized insert query

Question

I have this code to transfer records from one-table to the other

cmd2.CommandText = "select * from " + TableName;
                    reader = cmd2.ExecuteReader();
                    if (reader != null)
                    {

                        String s = "".PadLeft(reader.FieldCount - 1, 'X').Replace("X", "?,") + "?";
                        cmd.CommandText = String.Format("{0} into {1} values ({2})", insertorreplace, TableName, s);

                        StringBuilder sb = new StringBuilder();
                        while (reader.Read())
                        {
                            int i = 0;

                            for (i = 0; i < reader.FieldCount; ++i)
                            {
                                cmd.Parameters.AddWithValue(null,reader[i].ToString()); // data type issue
                            }
                            cmd.ExecuteNonQuery();
                        }
                        reader.Close();
                    }

Probably because of the commented line I get data type issue. I want all things to be passed by string.

Still looking for answers

Answer 1

If you're copying from one table to another, the best thing is to do it all in one query with INSERT INTO ... SELECT FROM.

To fix your code, just remove .ToString() from reader[i].