Decouple file-access logic

[ghost]

Hello there,
I wanted to implement a simple progress-tracking and noticed that the logic to read the file, and write it to the request-stream is implemented several times, slightly differently, violating e.g. DRY or SoC.

1. In the MultiPartStreamer class (here)
2. In the HttpRequest class (here).

If you agree that this is a problem, how would you solve it?
My proposals:

• A) Defining an interface like IFileDataProvider with a simple signature like WriteFileToStream(string path, Stream requestStream)
• B) A parameter like Action<string, Stream, long> streamWriter

I see the following advantages of this approach:

• Removes redundancy
• Ensures SoC
• Great flexibility: You don`t care if the file to upload is on your local computer, or a remote http resource