Cannot upload a file to a webservice and get the response in Json format

Question

I have a simple webservice that I would like to upload a file to. The problem is that I need the response in json.

Form my experience in order to get a response in Json my request has to have a content-type of 'application/json'. But ofcourse this cannot be the case with a file upload since the content type will have to be 'multipart/form-data'.

In my Json i want to return a value showing whether successful and a filename.

[WebMethod(EnableSession = true)]
[ScriptMethod(ResponseFormat = ResponseFormat.Json)]
public TyoeOfSomeObject UploadFile()
{
    // Get the file from the context and do something with it
    HttpPostedFile httpPostedFile = HttpContext.Current.Request.Files[0];

    // Return either a string or an object to serialise with the required values
    return SomeObject;
}

Answer 1

You could set the return type of your function to a string and then use some JSON serializer to serialize your object to JSON and return it as a JSON string. For JSON serialization I use Jayrock I believe ASP .NET has its own JSON libraries now as well.

Answer 2

You can declare your web method with byte[] as an output parameter. Then you can set ContentType and return any data you want.

If you use WCF instead of ASMX web service you can return Stream or Message in such cases (see http://stackoverflow.com/questions/3078397/returning-raw-json-string-in-wcf/3079326#3079326. You can try also return Stream instead of byte[] in the web service if your file is very large. Probably it will also works with ASMX web service.

http://stackoverflow.com/questions/3156279/asp-net-webservice-serialization/3156369#3156369

Answer 3

I was unable to find a way to return a response in json. I don't think its possible without tinkering with the inner workings. The solution I used was to create an aspx that could handle the file, you could ofcourse use .ashx or WCF as described by OLEG.