ADO.NET 2.0 driver throws exception on CreateCommand()

Question

I'm using ADO.NET 2.0 driver from Embracadero and trying to connect to remote Interbase base (http://cc.embarcadero.com/item/25497). I'm trying to do insert query to my database, but when I do insert query it throws "Object reference not set to an instance of an object." Does anybody have the same problem?

I have:

    public DbConnection GetConnection()
    {
        DbConnection con = new TAdoDbxConnection();
        con.ConnectionString = _connectionString;

        return con;
    }

and then I do:

        using (var conn = GetConnection())
        {
            using (var cmd = conn.CreateCommand())
            { 
                cmd.CommandText = query;

                var param = cmd.CreateParameter();// <---- here exception is thrown
                NazwaChannel.ParameterName = "@param";
                NazwaChannel.Value = 1000;
                NazwaChannel.DbType = DbType.Int32;

                cmd.Parameters.Add(param);

                conn.Open();
                cmd.ExecuteNonQuery();
                conn.Close();

            }
        }

query is like "Insert into Table (tableID, columnname) values (GEN_ID(GenaratorName, 1), @param)".

Well first of all, we need some code to be able to help you. Also, if you have a nullpointerexception, read [this](http://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it). — , Dec 27 '16 at 08:28
Just one suggestion. Grab the value of the query variable and try to insert in the DB directly to see if the problem is in the query. Otherwise I don't see anything wrong with your code. — st_stefanov, Dec 27 '16 at 08:48
And one more suggestion - try to open the connection for test just before the cmd.CreateParameter(); and see if you get the same or similar error on the conn.Open() line. Then we will know that it is related to establishing the connection with the remote DB. — st_stefanov, Dec 27 '16 at 08:53
When I do query like "Insert into tablename(id, param) values (uniqueId, 1)" everething is ok — Ant, Dec 27 '16 at 10:09
finally, it could be solved by adding conn.Open() before using cmd.CreateCommand() xD But now it throws exception unknown token "@". — Ant, Dec 27 '16 at 10:48

score 1 · Answer 1 · answered Dec 28 '16 at 22:34

1

The answer is:

using conn.Open() before parameter creation
instead of 'INSERT INTO TABLENAME (column1, column2, ...) VALUES (@value1, @value2, ...)' use 'INSERT INTO TABLENAME (column1, column2, ...) VALUES (? , ?, ...)'.

answered Dec 28 '16 at 22:34

Ant

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ADO.NET 2.0 driver throws exception on CreateCommand()

1 Answers1