Develop Reference

WebAPI - File download checksum?

I'm currently downloading a file from my Web API using a C# RestClient.
This is my current code for returning a file from the Web API part:
[HttpGet]
public HttpResponseMessage Generate()
{
var stream = new MemoryStream();
// processing the stream.
var result = new HttpResponseMessage(HttpStatusCode.OK)
{
Content = new ByteArrayContent(stream.GetBuffer())
};
result.Content.Headers.ContentDisposition =
new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment")
{
FileName = "CertificationCard.pdf"
};
result.Content.Headers.ContentType =
new MediaTypeHeaderValue("application/octet-stream");
return result;
}
Taken from this: How to return a file (FileContentResult) in ASP.NET WebAPI
My question is then, how can i validate that the file is downloaded correctly - can i somehow provide an MD5 checksum on the ByteArray and check this in the RestClient, or is this complete unnecessary?

You would generate a hash of the file, add it as a response header and verify when the download completes within the client.
This would only make sense if you think there is a chance of corruption of the data within your stream or network issues outside the ability of TCP error correction to handle.
How necessary this is is a judgement call, see Why is it good practice to compare checksums when downloading a file? for a discussion. (Considering the hash & data originate from the same place in the same response, the security considerations don't really apply)

Downloading xml file from URL

I am trying to store data from a xml file located in this link : Link to xml file
The xml file basically contains questions as well as options relating to English grammar. The main reason for saving these file is that I can parse these information later
From the browser (Chrome or IE), the xml file is loaded normally yet saving it programmatically did not work. The issue is that the data retrieved from that URL appeared to be something else.
This is my code for getting data from the URL
using (WebClient client = new WebClient())
{
client.Encoding = Encoding.UTF8;
// the data retrieved is something meaning : "Link does not exist"
string data = client.DownloadString("http://farm04.gox.vn/edu/IOE_Exam/IOE/l5/v1/g1/exam1.xml?v=");
}
The above approach gives nothing but a string which indicates there isnt such a link (though I still think the server itself sends it rather than a 404 error).
My second attempt is using WebRequest and WebResponse but no luck. I have read that WebClient is a wrapper class for the latter method so both give the same result
WebRequest request = WebRequest.Create(Url);
WebResponse response = request.GetResponse();
using (Stream stream = response.GetResponseStream())
{
return new StreamReader(stream).ReadToEnd();
}
I suppose the server has a mechanism to prevent client from downloading it. However Chrome would do the job successfully by loading the page then "Ctrl + S" (Save as ..) to save the xml file without any problems.
What the differences between browser and WebClient API ? Is there additional action which the browser implements ?
Any suggestion would be much appreciated.

How to stream data from another resource in c# WebApi

I'm working on an MVC webapplication that streams data from many resources.
My problem is when want to get data (music file) from a stream resource and then stream it to my web page, I don't know how not to download completely and then stream it to my web page.
Here is my webapi code:
[HttpGet]
public HttpResponseMessage Downlaod(int Data)
{
WebClient myWebClient = new WebClient();
Uri u =new Uri("https://api.soundcloud.com/tracks/" + Data + "/stream?client_id=*******************");
byte[] myDataBuffer = myWebClient.DownloadData(u);
MemoryStream st = new MemoryStream(myDataBuffer);
/*heres when i download data and convert it to memory stream*/
HttpResponseMessage result = new HttpResponseMessage(HttpStatusCode.OK);
result.Headers.AcceptRanges.Add("bytes");
result.StatusCode = HttpStatusCode.OK;
result.Content = new StreamContent(st);
result.Content.Headers.ContentLength = st.Length;
result.Content.Headers.ContentType =
new MediaTypeHeaderValue("application/octet-stream");
return result;
}
I want to stream immediately when I receive bytes from my resource.
note: I'm not asking about how to stream data to the client it's about streaming from server to server.
I want to get file from another server and stream it to my clients without downloading the full content before start streaming.
note2: I also don't want to download the full content in once because the full content is very big, I want to get a byte from my content and then send that byte to the client not downloading the full content.
I think I'm doing it in wrong way and it is not possible with an MVC application if anyone can introduce an application that can proxy bytes from destination to client it would be the answer. the main reason that I want this,is to proxy a music file from my content server to a javascript music player and not to expose the main file.

Downloading a file from server and save it in client

I am currently developing an ASP.net application, where I generate a word document in server and I want to save it in client machine who access that feature with out user interactions. How can I download it and save it in client machine, using Javascript?

you cann't save it in clients machine with out knowledge of client.
You can give a link of the word document,user need to click on the link and save it in his machine.
<a href="serverLink.doc" >Click to Save Word document</a>
Note: you cant do any manipulation on client PC by using Javascript or any scripting language

You can do either of this :
CASE 1 :
private static string GetWebTest1(string url)
{
System.Net.WebClient Client = new WebClient();
return Client.DownloadString(url);
}
CASE 2 :
private static string GetWebTest2(string url)
{
HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(url);
WebResponse response = request.GetResponse();
Stream stream = response.GetResponseStream();
StreamReader reader = new StreamReader(stream);
return reader.ReadToEnd();
}

Use System.Net.WebClient.DownloadFile and you are doing bulk downloads then do use WebClient.DownloadProgressChanged Event. Sometimes we do bulk download but user get the impression that system stuck or fail somewhere and start hitting refresh. Avoid that!

How to read a file from a URI using StreamReader?

I have a file at a URI that I would like to read using StreamReader. Obviously, this causes a problem since File.OpenText does not support URI paths. The file is a txt file with a bunch of html in it. I have multiple web pages that use this same piece of html, so I have put it in a txt file, and am reading it into the page when the page loads (I can get it to work when I put the file on the file system, but need to put it in a document repository online so that a business user can get to it). I am trying to avoid using an iframe. Is there a way to use StreamReader with URI formats? If not, what other options are there using C# to read in the txt file of html? If this is not optimal, can someone suggest a better approach?

Is there a specific requirement to use StreamReader? Unless there is, you can use the WebClient class:
var webClient = new WebClient();
string readHtml = webClient.DownloadString("your_file_path_url");

You could try using the HttpWebRequestClass, or WebClient. Here's the slightly complicated web request example. It's advantage over WebClient is it gives you more control over how the request is made:
HttpWebRequest httpRequest = (HttpWebRequest) WebRequest.Create(lcUrl);
httpRequest.Timeout = 10000; // 10 secs
httpRequest.UserAgent = "Code Sample Web Client";
HttpWebResponse webResponse = (HttpWebResponse) httpRequest.GetResponse();
StreamReader responseStream = new StreamReader(webResponse.GetResponseStream());
string content = responseStream.ReadToEnd();

If you are behind a proxy don't forget to set your credentials:
WebRequest request=WebRequest.Create(url);
request.Timeout=30*60*1000;
request.UseDefaultCredentials=true;
request.Proxy.Credentials=request.Credentials;
WebResponse response=(WebResponse)request.GetResponse();
using (Stream s=response.GetResponseStream())
...