Styjun

I have called a Blackboard Learn APIs to download a file. The Url is

https://blackboard.ddns.net/learn/api/public/v1/courses/uuid:d23e128e62f8483699c26836e06cab32/contents/_27_1/attachments/_13_1/download

When I click on the link on the browser I saw that there are 2 more 302 Found before getting content rendered on the browser.

https://blackboard.ddns.net/learn/api/public/v1/courses/uuid:d23e128e62f8483699c26836e06cab32/contents/_27_1/attachments/_13_1/download
Status code: 302

https://blackboard.ddns.net/bbcswebdav/xid-1407_1?VxJw3wfC56=1553768183&Kq3cZcYS15=6716bb2d5bc740c29eb11e01d75bc913&3cCnGYSz89=LhqjIQu9ReJ6IaoXzfPALpMer7momaz%2BwYxyWPG3YFY%3D
Status code: 302

https://blackboard.ddns.net/bbcswebdav/courses/1001/Blackboard%20code.txt?VxJw3wfC56=1553767343&Kq3cZcYS15=6716bb2d5bc740c29eb11e01d75bc913&3cCnGYSz89=uSziSDgibsV8PoWygH4spxpX7lOdDGwAvtlIHvrbPxM%3D
Status code: 200

I tried on the Postman by sending Bearer token and request a GET request to call the method and it also received the content.

I have to write C# code to receive the content of the file but I don't receive file but receive 500 InternalServerError. I have been trying to fix the issue but no luck. Do you have any thoughts on this? Please help.

My code in C# console application is as below:

static void Main(string[] args)

 //GET /learn/api/public/v1/courses/courseId/contents/contentId/attachments/attachmentId/download 
 string fileUrl = "/learn/api/public/v1/courses/uuid:d23e128e62f8483699c26836e06cab32/contents/_27_1/attachments/_13_1/download";

 using (HttpClient client = new HttpClient())
 
 client.BaseAddress = new Uri("https://blackboard.ddns.net/");
 client.DefaultRequestHeaders.Authorization =
 new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", "avnPkfmWSnf2Y5aKf1497LahLD3eKuwn");

 byte[] result = null;
 HttpResponseMessage response = client.GetAsync(fileUrl).Result;

 if (response.IsSuccessStatusCode)
 
 result = response.Content.ReadAsByteArrayAsync().Result;
 
 

After reading a post How can I get System.Net.Http.HttpClient to not follow 302 redirects?, I tried to follow the 302 redirections and change the code as below but got the same 500 InternalServerError at the end.

static void Main(string[] args)
 
 //GET /learn/api/public/v1/courses/courseId/contents/contentId/attachments/attachmentId/download 

 string fileUrl = "/learn/api/public/v1/courses/uuid:d23e128e62f8483699c26836e06cab32/contents/_27_1/attachments/_13_1/download";

 HttpClientHandler clientHander = new HttpClientHandler();
 clientHander.AllowAutoRedirect = false;

 using (HttpClient client = new HttpClient(clientHander))
 
 client.BaseAddress = new Uri("https://blackboard.ddns.net/");

 client.DefaultRequestHeaders.Authorization =
 new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", "avnPkfmWSnf2Y5aKf1497LahLD3eKuwn"); 

 byte[] result = null;

 HttpResponseMessage response = client.GetAsync(fileUrl).Result;

 if (response.StatusCode == System.Net.HttpStatusCode.Found)
 
 var locaton = response.Headers.Location.AbsoluteUri;
 HttpResponseMessage secondResponse = client.GetAsync(locaton).Result;
 if (secondResponse.StatusCode == System.Net.HttpStatusCode.Found)
 
 string finalUrl = secondResponse.Headers.Location.OriginalString;
 HttpResponseMessage thirdResponse = client.GetAsync(finalUrl).Result;
 result = thirdResponse.Content.ReadAsByteArrayAsync().Result;
 Console.Write(Encoding.UTF8.GetString(result));
 
 
 
 

I have tried with different HTTP clients available in .NET (HttpWebRequest/Response, WebClient, HttpClient), but always received 500 Internal Server Error. So, I decided to test with a third-party HTTP client and luckily RestSharp worked for me.

public ActionResult Index()

var client = new RestClient("https://blackboard.ddns.net/");

var request = new RestRequest("/learn/api/public/v1/courses/uuid:d23e128e62f8483699c26836e06cab32/contents/_27_1/attachments/_13_1/download", Method.GET); 

client.AddDefaultHeader("Authorization", "Bearer ZVAFzAuZ1ujYRENLrjNv3b8UWWvgRic4");

var response = client.Execute(request); 

return File(response.RawBytes, "text/plain", "MyTest.txt");