Im looking for solution how can I upload some file using http request. I got the idea that I'll transfer my files by post and on PHP side I'll put files on the server.
How doin this?
var client = new System.Net.WebClient();
client.UploadFile(address, filename);
See UploadFile on MSDN.
Well I'd try the simplest possible thing that might work to start with - WebClient.UploadFile:
WebClient client = new WebClient();
client.UploadFile(url, file);
Of course, you'll have to write appropriate PHP code to handle the upload...