Excel-fil er beskadiget efter udlæsning fra database

Hej
Jeg vil godt kunne gemme filer i en SQL-database samt at kunne udlæse filer fra databasen med VB.Net kode (koden har jeg fundet på nettet).

Jeg kan godt gemme en Excel fil i databasen, men når jeg prøver at udlæse filen, så skriver Excel en fejlmeddelelse om, at filen er beskadiget.

Håber på, at der er en ekspert i dette forum, som kan hjælp mig med at rette koden, så jeg kan gemme og udlæse filer.

******************************************************
***              Oprettelse af tabel (SQL)            ***
******************************************************

CREATE TABLE BLOBTest
(
TestID int IDENTITY(1,1),
BLOBName varChar(50),
BLOBData varBinary(MAX)
)
******************************************************
***              Indsætter fil i tabel (SQL)            ***
******************************************************
INSERT INTO BLOBTest
    (BLOBName, BLOBData)
    SELECT 'First test file',
        BulkColumn FROM OPENROWSET(
            Bulk 'C:\test\test.xlsx', SINGLE_BLOB) AS BLOB

******************************************************
***                  Udlæsning af fil (VB.Net)        ***
******************************************************

    Public Sub fileStream()
        Dim connection As SqlConnection = New SqlConnection("Data Source=(local);Initial Catalog=Test;Integrated Security=True")

        Try
            connection.Open()
            TextBox1.Text += ("Database er åben!")
            connection.Close()
        Catch ex As Exception
            TextBox1.Text = +("Database kunne ikke åbnes!")
        End Try

        ' Assumes that connection is a valid SqlConnection object.
        Dim command As SqlCommand = New SqlCommand("SELECT * FROM BLOBTest", connection)

        ' Writes the BLOB to a file.
        Dim stream As FileStream
        ' Streams the binary data to the FileStream object.
        Dim writer As BinaryWriter
        ' The size of the BLOB buffer.
        Dim bufferSize As Integer = 100
        ' The BLOB byte() buffer to be filled by GetBytes.
        Dim outByte(bufferSize - 1) As Byte
        ' The bytes returned from GetBytes.
        Dim retval As Long
        ' The starting position in the BLOB output.
        Dim startIndex As Long = 0

        ' Open the connection and read data into the DataReader.
        connection.Open()
        Dim reader As SqlDataReader = command.ExecuteReader(CommandBehavior.SequentialAccess)

        Do While reader.Read()
            ' Get the publisher id, which must occur before getting the logo.
            'pubID = reader.GetString(0)

            ' Create a file to hold the output.
            stream = New FileStream("c:\test\" & "test" & ".xlsx", FileMode.OpenOrCreate, FileAccess.Write)
            writer = New BinaryWriter(stream)

            ' Reset the starting byte for a new BLOB.
            startIndex = 0

            ' Read bytes into outByte() and retain the number of bytes returned.
            retval = reader.GetBytes(2, startIndex, outByte, 0, bufferSize)

            ' Continue while there are bytes beyond the size of the buffer.
            Do While retval = bufferSize
                writer.Write(outByte)
                writer.Flush()

                ' Reposition start index to end of the last buffer and fill buffer.
                startIndex += bufferSize
                retval = reader.GetBytes(2, startIndex, outByte, 0, bufferSize)
            Loop

            'Write the remaining buffer.
            writer.Write(outByte, 0, retval - 1)
            writer.Flush()

            ' Close the output file.
            writer.Close()
            stream.Close()
        Loop

        ' Close the reader and the connection.
        reader.Close()
        connection.Close()
    End Sub