(C# UWP/WinRT) Building a multipart/form-data Request for HTTP Upload

Uploading files to a web server typically requires building a multipart/form-data request where the files are contained in the sub-parts of the MIME request.

Note: HTTP uploads require code on the server-side to receive the upload. For example, see Complete C# ASP.NET HTTP Upload Example

This example produces the following HTTP multipart/form-data request:

POST /something HTTP/1.1
Content-Type: multipart/form-data; boundary=------------070002080409050901090203
Host: domain
Content-Length: 546

--------------070002080409050901090203
Content-Disposition: form-data; name="fileA"; filename="fileA.txt"
Content-Type: text/plain

This is the contents of file A
--------------070002080409050901090203
Content-Disposition: form-data; name="fileB"; filename="fileB.txt"
Content-Type: text/plain

This is the contents of file B
--------------070002080409050901090203
Content-Disposition: form-data; name="fileC"; filename="fileC.txt"
Content-Type: text/plain

This is the contents of file C
--------------070002080409050901090203--

Chilkat Universal Windows Platform (UWP) / WinRT Downloads Chilkat for the Universal Windows Platform (UWP)

// This example demonstrates building a multipart/form-data request.

Chilkat.HttpRequest req = new Chilkat.HttpRequest();

// The ContentType, HttpVerb, and Path properties should
// always be explicitly set.
req.HttpVerb = "POST";
req.Path = "/something";
req.ContentType = "multipart/form-data";

// The contents and name of each file to be uploaded is provided
// by calling any of the following methods:
// AddBytesForUpload
// AddBytesForUpload2
// AddFileForUpload
// AddFileForUpload2
// AddStringForUpload
// AddStringForUpload2

// For this example, we'll provide the contents of the files to be uploaded
// directly as in-memory strings.
req.AddStringForUpload("fileA","fileA.txt","This is the contents of file A","utf-8");
req.AddStringForUpload("fileB","fileB.txt","This is the contents of file B","utf-8");
req.AddStringForUpload("fileC","fileC.txt","This is the contents of file C","utf-8");

// View the request that would be sent if SynchronousRequest was called:
string requestMime = req.GenerateRequestText();
Debug.WriteLine(requestMime);

// A few important comments about the HTTP request that is generated:
// 
// 1) Chilkat automatically generates a random boundary string.   In 99.999% of cases, this should 
//    be sufficient.
// 2) The Content-Length header is automatically generated based on the actual length of the MIME message
//    that follows the intial (topmost) MIME header.
// 3) The HOST header will automatically get filled in with the actual domain when SynchronousRequest
//    is called