Parameterized SQL commands

[David Dvali]

Hello.
I'm using NET Connector and want to instal some data to my table with parameterized SQL commands.
I wrote (C#):
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MySqlCommand mySqlCommand = new MySqlCommand("INSERT INTO table1 (userid) VALUES (@userid)", mySqlConnection);
mySqlCommand.Parameters.Add("@userid", "David");
mySqlConnection.Open();
mySqlCommand.ExecuteNonQuery();
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And after this it always inserts NULL value in userid field:(.
With textual data I can go without parameterized SQL, but how can I store binary data in BLOB fields?