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To write a file to a database, we need to convert the file to a byte array, then use the byte array as a parameter to an INSERT query.

The following code opens a file using a FileStream object, reads it into a byte array, and inserts it into the file table:

Visual Basic Example
Dim conn As New MySqlConnection
Dim cmd As New MySqlCommand
Dim SQL As String
Dim FileSize As UInt32
Dim rawData() As Byte
Dim fs As FileStream
conn.ConnectionString = "server=;" _
    & "uid=root;" _
    & "pwd=12345;" _
    & "database=test"
    fs = New FileStream("c:\image.png", FileMode.Open, FileAccess.Read)
    FileSize = fs.Length
    rawData = New Byte(FileSize) {}
    fs.Read(rawData, 0, FileSize)
    SQL = "INSERT INTO file VALUES(NULL, @FileName, @FileSize, @File)"
    cmd.Connection = conn
    cmd.CommandText = SQL
    cmd.Parameters.AddWithValue("@FileName", strFileName)
    cmd.Parameters.AddWithValue("@FileSize", FileSize)
    cmd.Parameters.AddWithValue("@File", rawData)
    MessageBox.Show("File Inserted into database successfully!", _
    "Success!", MessageBoxButtons.OK, MessageBoxIcon.Asterisk)
Catch ex As Exception
    MessageBox.Show("There was an error: " & ex.Message, "Error", _
        MessageBoxButtons.OK, MessageBoxIcon.Error)
End Try
C# Example
MySql.Data.MySqlClient.MySqlConnection conn;
MySql.Data.MySqlClient.MySqlCommand cmd;
conn = new MySql.Data.MySqlClient.MySqlConnection();
cmd = new MySql.Data.MySqlClient.MySqlCommand();
string SQL;
UInt32 FileSize;
byte[] rawData;
FileStream fs;
conn.ConnectionString = "server=;uid=root;" +
    fs = new FileStream(@"c:\image.png", FileMode.Open, FileAccess.Read);
    FileSize = fs.Length;
    rawData = new byte[FileSize];
    fs.Read(rawData, 0, FileSize);
    SQL = "INSERT INTO file VALUES(NULL, @FileName, @FileSize, @File)";
    cmd.Connection = conn;
    cmd.CommandText = SQL;
    cmd.Parameters.AddWithValue("@FileName", strFileName);
    cmd.Parameters.AddWithValue("@FileSize", FileSize);
    cmd.Parameters.AddWithValue("@File", rawData);
    MessageBox.Show("File Inserted into database successfully!",
        "Success!", MessageBoxButtons.OK, MessageBoxIcon.Asterisk);
catch (MySql.Data.MySqlClient.MySqlException ex)
    MessageBox.Show("Error " + ex.Number + " has occurred: " + ex.Message,
        "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);

The Read method of the FileStream object is used to load the file into a byte array which is sized according to the Length property of the FileStream object.

After assigning the byte array as a parameter of the MySqlCommand object, the ExecuteNonQuery method is called and the BLOB is inserted into the file table.