Download file from sharepoint rest service - sharepoint

Question

When im trying to use following code to download file from sharepoint site using rest services
I was getting Remote server returned 403 forbidden - Please help
String fileurl = "exact sharepoint file url";
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(fileurl);
NetworkCredential credential = new NetworkCredential("username", "password","domain");
//request.Credentials = credential;
//request.ContinueTimeout = 10000;
request.Credentials = credential;
request.Headers["UserAgent"] = "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US) AppleWebKit/533.4 (KHTML, like Gecko) Chrome/5.0.375.99 Safari/533.4";
request.Accept = "/";
// request.Headers["Accept"] = "/";
WebResponse resp = await request.GetResponseAsync();

Answer 1

To be able to download file from SharePoint Online/Office 365 using CSOM or REST the authentication has to be performed.
About SharePoint Online authentication
Since SharePoint Online (SPO) uses claims based authentication, you could consider the following options:
SharePointOnlineCredentials class as part of SharePoint Online
Client Components SDK provides credentials to access SharePoint
Online resources.
utilize a custom implementation, for example as explained in this great
article. The article contains code sample with class MsOnlineClaimsHelper class that implements claim-based authentication for SharePoint Online.
Consume SharePoint REST service using .NET
In order to consume SharePoint REST service using .NET you could consider the following approaches:
HttpClient - Provides a base class for sending HTTP requests and receiving HTTP responses from a resource identified by a URI. (.NET Framework 4.5)
WebClient - provides common methods for sending data to and receiving data from a resource identified by a URI. (.NET Framework 1.1)
HttpWebRequest - provides an HTTP-specific implementation of the WebRequest class, more low-level then the previous ones (.NET Framework 1.1)
All of them allows to download a file from SharePoint Online.
Examples
Example 1. How to specify SPO credentials using SharePointOnlineCredentials class
var request = (HttpWebRequest)WebRequest.Create(endpointUri);
request.Credentials = new SharePointOnlineCredentials(username, securedPassword);
//...
Example 2. How to specify SPO authentication cookies using MsOnlineClaimsHelper class:
var claimshelper = new MsOnlineClaimsHelper(webUri, userName, password);
var endpointUri = new Uri(webUri,string.Format("/_api/web/getfilebyserverrelativeurl('{0}')/$value", fileUrl));
var request = (HttpWebRequest)WebRequest.Create(endpointUri);
request.Headers.Add("X-FORMS_BASED_AUTH_ACCEPTED", "f");
request.Method = "GET";
request.CookieContainer = claimshelper.CookieContainer;
//...
Key points:
SharePoint Auth cookies are passed via CookieContainer property
According to Files and folders REST API reference the following
endpoint is used to retrieve file content: <app web
url>/_api//web/getfilebyserverrelativeurl('<file url>')/$value

Answer 2

try this one :
using System.Net;
using (WebClient webClient = new WebClient ())
{
webClient.DownloadFile(fileurl , filename);
}

Answer 3

try this one. let me know it will work or not?
HttpResponseMessage response = Request.CreateResponse(HttpStatusCode.OK);
response.Content = new StreamContent(new FileStream(HttpContext.Current.Server.MapPath("~/Documents/" + documentFileName.Name), FileMode.Open, FileAccess.Read));
response.Content.Headers.ContentDisposition = new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment");
response.Content.Headers.ContentDisposition.FileName = documentFileName.Name;
response;