vb.net - How to access into a private repository's .diff of GitHub in vb .net with WebRequest credentials -

i want access .diff file of private repository of github. have following code, doesn't work.

dim myreq httpwebrequest = webrequest.create(url) dim netcred networkcredential = new networkcredential("usr", "pass") dim credentials icredentials = netcred.getcredential(url, "basic") myreq.credentials = credentials myreq.preauthenticate = true try     dim response httpwebresponse = ctype(myreq.getresponse(), httpwebresponse) catch ex system.net.webexception     messagebox.show(ex.message) end try 

there wrong? message webexception contains "error in remote server. (404) not found"