Custom Post function to upload a file in Self Hosted REST API - vb.net

Question

I have written a VB.Net Visual basic console application for Self hosting a custom file upload service to be consumed by an application. Concept being the end user uses the application to generate data, when completed the file is uploaded to our server without user intervention. I have complete control over both applications. The problem is I can't figure out the POST Upload signature that can accept several params, including the file or how to actually receive the file. The User application is in beta now, testing all other functionality excluding the "Send File" sub's. I've never seen a file larger then 180 KB; I plan on accepting files sizes up to 1 MB. This lets me place some limitations (and filters) to help avoid abuse of the service.
I'm using NuGet packages webapi.client (4.0.30506), webapi.selfhost (4.0.3056) (and their associated required packages) and newtonsoft.json (4.5.11) and PostMan to test/debug the process. I'm using Visual Studio 2019 (Fully patched and up to date). All of the examples and google research point only to C# (not my language of choice), or are for hosted solutions like IIS.
In Postman, the only place where filenames are accepted are in the body, form-data. So, there is where I set up my key/value pairs with matching (including case and order) the params as defined in the FileULRequest class.
Everything that I've tried returns either
'500 internal server error'
or
"Message": "No HTTP resource was found that matches the request URI 'http://10.0.1.102:21212/file/upload/'."
The class object of the request looks like this:
Public Class FileULRequest
Public Property EncToken As String 'Holds an encrypted token for authorization
Public Property Filename As String 'Holds a recommended file name
Public Property AppID As String 'Holds the client/app ID for simpler server actions
Public Property File As Byte() 'Not sure if this is the right type/ should be the encrypted file contents.
End Class
The POST function signature currently looks like this:
Imports System.Web.Http
Namespace Controllers
Public Class FileController
Inherits ApiController
Public Function PostUpload(<FromBody()> ByVal ObjRequest As FileULRequest) As String
Return ""
End Function
End Class
End Namespace
In the Sub Main I have: (note, this is cleaned out)
Sub Main()
API_URL = Dns.GetHostByName(Dns.GetHostName()).AddressList(0).ToString()
Dim ThisConfig As New HttpSelfHostConfiguration("HTTP://" & API_URL & ":" & API_PORT)
ThisConfig.Routes.MapHttpRoute(name:="FileUpload", routeTemplate:="{controller}/{ObjRequest}", defaults:=New With {.id = RouteParameter.Optional})
ThisConfig.MaxConcurrentRequests = API_MaxCon
Dim Config As HttpSelfHostConfiguration = ThisConfig
Using Webserver As New HttpSelfHostServer(Config)
Try
Webserver.OpenAsync().Wait() 'Start the web server
Console.WriteLine("Listening at: " & API_URL & ":" & API_PORT) 'use the URL & port defined
Console.WriteLine("Enter to end")
Catch ex As Exception
Console.WriteLine("Error:{0}", ex.Message.ToString)
Console.WriteLine("Enter to end")
Console.ReadLine()
End
End Try
Dim Cmd As String = UCase(Console.ReadLine())
End
End Using
End Sub
API_Port and API_MaxCon are properties stored in the Appsettings.
What I'm trying to do is set the FileULRequest object params, post this to the service, confirm & validate the data and, if successful, save the file onto a network share. I've tried a large number of different combinations and nothing seems to get close; I cant get inside the Post event in the debugger to figure out or test anything.