Using statement in Task
asp.net-web-api, c#, task-parallel-library, using
Solution
- `MemoryStream` is one of the classes that implement `IDisposable`, because their base class does. `MemoryStream` doesn't hold any resources (apart from managed memory), so disposing it is actually unnecessary.
- `HttpResponseMessage` is disposable. This means that when the whole response it sent, that object is disposed. Doing that disposes the contained `HttpContent`, which in the case of `StreamContent` disposes the underlying `Stream`. So even if you had a `Stream` that should be disposed, you don't have to worry about it in this case.
Problem
In an ASP.NET Web API controller I want to return an image. For streaming the image I need a `MemoryStream`. Normally I would wrap it in a `using` statement in order to make sure it gets properly disposed afterwards. However, as this executes asynchronously in a `Task` this doesn't work: ``` public class ImagesController : ApiController { private HttpContent GetPngBitmap(Stream stream) { var pngBitmapEncoder = new PngBitmapEncoder(); pngBitmapEncoder.Save(stream); stream.Seek(0, SeekOrigin.Begin); return new StreamContent(stream); } // GET api/images public Task<HttpResponseMessage> Get(string id, string path) { //do stuff return Task.Factory.StartNew(() => { var stream = new MemoryStream(); //as it's asynchronous we can't use a using statement here! { var response = new HttpResponseMessage(HttpStatusCode.OK) { Content = GetPngBitmap(stream) }; response.Content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue("image/png"); return response; } //how can I dispose stream??? }); } } ```