Vb.net webapi file download troubles - vb.net

Question

We've been using an IIS filehandler to download files that are stored in a database such as PowerPoint. Now we're trying to switch to webapi. File uploads are working fine but downloads are not.
Using the filehandler the url is like: http://localhost:57851/docmgr?id=6202 which returns a valid file with the following info from Fiddler:
Using the same code in a webapi controller having a url of: http://localhost:57851/webapi/file/GetFile?id=6202 returns a file with additional bytes added. Fiddler data:
Note the change in content-type as well even though the content-type is expressly set to "application/vnd.ms-powerpoint".
I must be missing something....
Here is the controller code:
<HttpGet>
Public Function GetFile()
Dim dbConn As New SqlConnection(DigsConnStr)
Dim dbCmd As New SqlCommand
Dim dbRdr As SqlDataReader
Dim id As String = HttpContext.Current.Request.QueryString("id")
Dim bytes As Byte()
Dim contentType As String
Dim fileName As String
Dim fileExt As String
Try
dbConn.Open()
dbCmd.Connection = dbConn
dbCmd.CommandText = "GET_FileForDownload"
dbCmd.CommandType = CommandType.StoredProcedure
dbCmd.Parameters.AddWithValue("#VirtualFileRecID", id)
dbRdr = dbCmd.ExecuteReader
dbRdr.Read()
contentType = dbRdr("ContentType")
bytes = dbRdr("FileBytes")
fileExt = dbRdr("FileExtension")
If contentType <> "" Then
fileName = dbRdr("Title") & fileExt
HttpContext.Current.Response.ContentType = contentType
HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment; filename=" & fileName)
HttpContext.Current.Response.BinaryWrite(bytes)
'HttpContext.Current.Response.Flush()
End If
dbConn.Close()
Catch ex As Exception
dbConn.Close()
Finally
If Not (dbConn Is Nothing) Then dbConn.Close()
End Try
End Function

Answer 1

WebAPI is going to wrap your response in XML (or whatever formatter you have in your webapiconfig class)
You really shouldn't access the response stream directly with WebAPI but you can return a HttpResponseMessage object with the file stream
Check this out
<HTTPGET>
Public Function GetFile(FileID as Integer) As HttpResponseMessage
Dim path = "C:\Temp\test.exe"
Dim result As New HttpResponseMessage(HttpStatusCode.OK)
Dim stream = New FileStream(path, FileMode.Open)
result.Content = New StreamContent(stream)
result.Content.Headers.ContentType = New MediaTypeHeaderValue("application/octet-stream")
Return result
End Function
Then you should really access it like this: http://localhost:57851/docmgr/6202