Retrieve MySQL Blob - Save The File To Disk

I have a mySQL table(IMP_SCANS) holding the file, it's name and size for every document:

scan_1 blob
description varchar
filesize int
doc_no varchar
doc_date date

I managed to insert a file to the table. Now I need to save the file to disk.

So I have the code:

Dim conn As New MySqlConnection
Dim cmd As New MySqlCommand
Dim myData As MySqlDataReader
Dim SQL As String
Dim FileSize As UInt32
Dim fs As FileStream

[CODE]............

I all works fine up to the line: myData.GetBytes(myData.GetOrdinal("scan_1"), 0, rawData, 0, filesize) Where it says "Object reference not set to an instance of an object". I cannot figure out why I receive this error.