I am trying to upload files (.docx, .pptx, .pdf) to an online MySQL database and later be able to save/download it locally to my pc. I am trying to develop a software that could do this particular task using VB.NET and MySql.

I have a tbl_proposals with fields:
- id
- doc_name
- created_by
- date_uploaded
- client_name
- description
- raw_file (mediumblob)
- file_format

This is my codes for uploading to the database and so far it seems to be working fine:

Dim fs As New System.IO.FileStream(filepath, IO.FileMode.Open, IO.FileAccess.Read)
            'filepath contains actual file path e.g. c:\documents\words.docx
            Dim doc(fs.Length() - 1) As Byte

            fs.Read(doc, 0, doc.Length)

            com.CommandText = "INSERT INTO tbl_proposals (doc_name, created_by, date_uploaded, client_name, description, raw_file, file_format) VALUES(@dname, @cby, @duploaded, @cname, @desc, @rfile, @fformat)"
            com.Parameters.AddWithValue("@dname", fname)
            com.Parameters.AddWithValue("@cby", uname)
            com.Parameters.AddWithValue("@duploaded", Now.Date)
            com.Parameters.AddWithValue("@cname", txtClient.Text)
            com.Parameters.AddWithValue("@desc", txtDesc.Text)

            Dim raw_file_param As New MySqlParameter("@rfile", MySqlDbType.MediumBlob, doc.Length, ParameterDirection.Input, False, 0, 0, Nothing, DataRowVersion.Current, doc)

            com.Parameters.AddWithValue("@fformat", ext)

            MessageBox.Show("Upload complete.", "Upload Status", MessageBoxButtons.OK, MessageBoxIcon.Information)

and this is where i'm having problems - my download codes

ofd.SelectedPath = "C:\"
        ofd.Description = "Choose where to save Proposal / Quote"

        If ofd.ShowDialog() = Windows.Forms.DialogResult.OK Then
            file_path = ofd.SelectedPath
        End If

        com.CommandText = "SELECT * FROM tbl_proposals WHERE doc_name = '" & selected_file & "'"
        reader = com.ExecuteReader()

        If reader.Read Then
            file_path = file_path & "\" & reader.GetString(1) & reader.GetString(7)
            Dim fs As New System.IO.FileStream(file_path, IO.FileMode.Create, FileAccess.ReadWrite)
            Dim raw_col As Integer = 7 'column # of raw data
            Dim raw_data(reader.GetBytes(raw_col, 0, Nothing, 0, Integer.MaxValue) - 1) As Byte

            reader.GetBytes(raw_col, 0, raw_data, 0, raw_data.Length)

            fs.Write(raw_data, 0, raw_data.Length)
        End If


the line "Dim raw_data(reader.GetBytes(raw_col, 0, Nothing, 0, Integer.MaxValue) - 1) As Byte" returns an exception: GetBytes can only be called on binary or guid columns

I tried to check what's the cause of this exception and understood that the data type in my database should be in VARBINARY. I tried doing that and gave me the same result. also tried using LONGBLOB and MEDIUMBLOB and still the same.

I hope someone can help me here. Thank you.

  • Jun S.

Line 14 should be: Dim raw_col As Integer = 6 'column # of raw data

Column ordinals are zero-based so indices are as follows
- id = 0
- doc_name = 1
- created_by = 2
- date_uploaded = 3
- client_name = 4
- description = 5
- raw_file (mediumblob) = 6
- file_format = 7
Your code read the file_format column and gave the error.