ASP. NET asynchronous Web API + jQuery Ajax File upload Code small analysis

The example actually applies the jquery Ajax (Web Client) + Async Web API to double-async.

jquery Ajax Post

1 $.ajax ({2Type: "POST",3URL: "/api/fileupload",4ContentType:false,5ProcessData:false,6 Data:data,7Successfunction(results) {8 showuploadcontrols ();9$ ("#uploadResults"). empty ();Ten          for(i = 0; i < results.length; i++) { One$ ("#uploadResults"). Append ($ ("<li/>")). Text (results[i])); A         } -     }, -Errorfunction(XHR, ajaxoptions, thrownerror) { the showuploadcontrols (); - alert (xhr.responsetext); -     } -});

The client sends the data as a post. The callback script is defined at success where the upload succeeds.

Async Web API

The controller action return value is task<tresult> In this case, it is defined as follows:

1  Public task<ienumerable<string>> Post ()2{3     ...        4 }

and the specific asynchronous effect is embodied in "file content read" and "Follow-up processing".

1 stringFullPath = HttpContext.Current.Server.MapPath ("~/uploads");2Custommultipartformdatastreamprovider Streamprovider =NewCustommultipartformdatastreamprovider (fullPath);3 varTask = Request.Content.ReadAsMultipartAsync (Streamprovider). ContinueWith (t =4 {5     if(t.isfaulted | |t.iscanceled)6         Throw Newhttpresponseexception (httpstatuscode.internalservererror);7 8     varFileInfo = StreamProvider.FileData.Select (i =9     {Ten         varinfo =NewFileInfo (i.localfilename); One         return "File saved as"+ info. FullName +" ("+ info. Length +")"; A     }); -     returnFileInfo; -  the});

Readasmultipartasync

(from MSDN) reads all the body parts of a MIME multipart message and generates a set of httpcontent instances as a result by using the Streamprovider instance to determine where each body part of the content is written.

Task.continuewith<tresult>

Creates a continuation task that executes asynchronously when the target Task completes. Specifically, in this example, when the Readasmultipartasync (read) task finishes, the behavior defined in ContinueWith is executed asynchronously as a continuation.

Multipartformdatastreamprovider Object

A imultipartstreamprovider that is suitable for use with HTML file uploads to write file contents to FileStream. The stream provider will view the <b>Content-Disposition</b> header field and determine the output stream based on whether the <b>filename</b> parameter exists. If the <b>filename</b> parameter is present in the <b>Content-Disposition</b> header field, the body part is written to FileStream, otherwise the body part is written The MemoryStream. This makes it easier to handle MIME multipart HTML form data as a combination of form data and file content.

tips: lambda expression inversion, from filedata to ienumerable<string>

1 var fileInfo = streamProvider.FileData.Select (i =2{3     var ) New  FileInfo (i.localfilename); 4     return " "" ("")"; 5 });

Sample code

ASP. NET asynchronous Web API + jQuery Ajax File upload Code small analysis