Question

I have got this WebService that allows uploading/downloading any docs (mostly .docx, .doc, .pdf) and all it returns is byte[] when querying for downloading.

I have written this code

 string ContractGUID = dtContract.Rows[0]["ContractGUID"].ToString();

 //Get Bytes from WebService
 byte[] fileData = BLL.Contract.GetDocument(new Guid(ContractGUID));
 Response.Clear();
 Response.BinaryWrite(fileData);
 Response.AddHeader("Content-Disposition", "Attachment");
 Response.Flush();

The other methods that the WebService exposed are GetDocumentName and GetDocumentLen

Is it possible to determine the Mime-Type or force the browser to download it in the right format? Currently it is downloading as .htm in Chrome and when open, I see funny characters. Any better advice?

Thanks.

Answer 1

No, it’s not possible to force the browser to download in the right format without you telling it via the Content-Type header.

Response.ContentType = "application/pdf"; //or whatever appropriate

If the web service exposes a GetDocumentName() method you can probably infer the appropriate format by looking at the name, assuming the name has a file extension. This, obviously, is not bullet proof since you can change the extension of a file to anything you want.

Another alternative would be to try and guess the file format by peeking at the first bytes. For example, if the first 4 bytes of the file are 25 50 44 46 then it’s very likely that this is a PDF file. On this website, they have a pretty extensive list.

Here’s the list of possible content-type headers.