从WEB API控制器返回Async方法中的Void [英] Returning Void in Async method from WEB API Controller
问题描述
我从此博客获得的ASP.NET MVC 4 WEB API控制器内部有此异步方法: http://www.strathweb.com/2012/04/html5-drag-and-drop-asynchronous-multi-file-upload-with-asp-net-webapi/
I have this async method inside ASP.NET MVC 4 WEB API Controller that I got from this blog: http://www.strathweb.com/2012/04/html5-drag-and-drop-asynchronous-multi-file-upload-with-asp-net-webapi/
public async Task<IList<RecivedFile>> Post()
{
List<RecivedFile> result = new List<RecivedFile>();
if (Request.Content.IsMimeMultipartContent())
{
try
{
MultipartFormDataStreamProvider stream = new MultipartFormDataStreamProvider(HostingEnvironment.MapPath("~/USER-UPLOADS"));
IEnumerable<HttpContent> bodyparts = await Request.Content.ReadAsMultipartAsync(stream);
IDictionary<string, string> bodyPartFiles = stream.BodyPartFileNames;
IList<string> newFiles = new List<string>();
foreach (var item in bodyPartFiles)
{
var newName = string.Empty;
var file = new FileInfo(item.Value);
if (item.Key.Contains("\""))
newName = Path.Combine(file.Directory.ToString(), item.Key.Substring(1, item.Key.Length - 2));
else
newName = Path.Combine(file.Directory.ToString(), item.Key);
File.Move(file.FullName, newName);
newFiles.Add(newName);
}
var uploadedFiles = newFiles.Select(i =>
{
var fi = new FileInfo(i);
return new RecivedFile(fi.Name, fi.FullName, fi.Length);
}).ToList();
result.AddRange(uploadedFiles);
}
catch (Exception e)
{
}
}
return result;
}
我的问题是，为什么此方法确切地具有Task的返回类型?尚不清楚它返回此任务的在哪里"或向谁"?就像没有人在等待/接收返回的对象一样.
My question is why exactly does this method have a return type of Task? It is not clear "where to" or "to whom" it returns this task? It's like there is no one that waits for/receives the returned object.
我想知道如果我这样返回void会带来什么影响:
I wonder what will be the implications if I return void like this:
我已经尝试过下面的代码，但它完全破坏了程序.就像运行时失去了对代码的引用，代码本身并没有完成运行.
public async void Post()
{
List<RecivedFile> result = new List<RecivedFile>();
if (Request.Content.IsMimeMultipartContent())
{
try
{
MultipartFormDataStreamProvider stream = new MultipartFormDataStreamProvider(HostingEnvironment.MapPath("~/USER-UPLOADS"));
IEnumerable<HttpContent> bodyparts = await Request.Content.ReadAsMultipartAsync(stream);
IDictionary<string, string> bodyPartFiles = stream.BodyPartFileNames;
IList<string> newFiles = new List<string>();
foreach (var item in bodyPartFiles)
{
var newName = string.Empty;
var file = new FileInfo(item.Value);
if (item.Key.Contains("\""))
newName = Path.Combine(file.Directory.ToString(), item.Key.Substring(1, item.Key.Length - 2));
else
newName = Path.Combine(file.Directory.ToString(), item.Key);
File.Move(file.FullName, newName);
newFiles.Add(newName);
}
}
catch (Exception e)
{
}
}
}
推荐答案
ASP.NET运行时正在等待它.您可能会发现此视频很有用.
The ASP.NET runtime waits for it. You may find this video useful.
async的大多数示例均假定UI上下文. ASP.NET 也提供了上下文，但这是请求"上下文-每个HTTP请求一个.我的 async/await帖子概述了此上下文"，以及 async/
Most examples for async assume a UI context. ASP.NET also provides a context, but it's a "request" context - one for each HTTP request. My async/await post gives an overview of this "context", and the async/await FAQ goes into much more detail.
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