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相信已經有很多文章來介紹ASP.Net Web API 技術，本系列文章主要介紹如何使用數據流，HTTPS，以及可擴展的Web API 方面的技術，系列文章主要有三篇內容。

主要內容如下：

I ?數據流

II 使用HTTPS

III 可擴展的Web API 文檔

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項目環境要求

• VS 2012（SP4）及以上，
• .Net 框架4.5.1
• Nuget包,可在packages.config 文件中查尋

本文涉及的知識點

ActionFilter

AuthorizationFilter

DelegateHandler

Different Web API routing 屬性

MediaTypeFormatter

OWIN

Self Hosting

Web API 文檔及可擴展功能

.Net 框架

Async/Await

.NET reflection

Serialization

ASP.NET Web API/MVC Error handling

IIS ,HTTPS 及Certificate

設計準則及技術

前言

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自從ASP.NET MVC 4之后.Net 框架開始支持ASP.NET Web API ，ASP.NET Web API 基于HTTP 協議建立的，是構建 RESTful 服務和處理數據的理想平臺，旨在使用HTTP 技術實現對多平臺的支持。

ASP.NET Web API 以request-response 的消息轉換模式為主，客戶端向服務器發送請求，服務器端響應客戶端請求。響應可同步或異步。

?個人認為使用Web API創建應用需要注意的三個關鍵點：

• 采用服務及方法滿足的目標
• 每個方法的輸入，如請求
• 每個方法的輸出，如響應

通常情況下，Asp.Net Web API 定義method語法與HTTP方法一一對應的，如自定義方法名?GetPysicians()，則與HTTP中Get 方法匹配。下圖是常用匹配表。

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但是此方法在很多情況下，并不實用，假如你想在單個API controller 類中定義多個Get 或Post 方法，在這種情況下，需要定義包含action 的路徑，將Action 作為URI 的一部分。以下是配置代碼：

1: public static void Register(HttpConfiguration config) 2: { 3: // Web API configuration and services 4: // Web API routes 5: config.MapHttpAttributeRoutes(); 6: 7: config.Routes.MapHttpRoute(name: "PhysicianApi", 8: routeTemplate: "{controller}/{action}/{id}", 9: defaults: new { id = RouteParameter.Optional }); 10: }

但是此方法不足以應對所有情況，如果想實現從中央倉庫刪除文件，并且想調用同一個方法來獲取文件，這種情況下，Web API 框架需要偽裝Get 及Delete對應的HTTP 方法屬性。如圖所示：

RemoveFile 方法可被Delete(HttpDelete) 或 Get(HttpGet)方法同時調用，從某種程度來說，HTTP 方法使開發人員命名?API“方法”變得簡單而標準。

Web API框架也提供了一些其他功能來處理路徑方面的問題，與MVC 的路徑處理方法相似。因此可定義不同類型的Action方法。?

數據流

網絡App 最常見的執行操作就是獲取數據流。ASP.NET Web API 能夠處理客戶端與服務器端傳輸的重量級的數據流，數據流可來源于目錄文件，也可是數據庫中的二進制文件。本文主要介紹兩種方法“Download”和“Upload”實現數據流相關的功能，Download是從服務器下載數據操作，而Upload則是上傳數據到服務器。

相關項目

• WebAPIDataStreaming
• WebAPIClient
• POCOLibrary

在對代碼解釋之前，首先來了解如何配置IIS（7.5）和Web API 服務Web.Config 文件。

1. 保證Downloads/Uploads 涉及的文件具有讀寫權限。

2. 保證有足夠容量的內容或因公安空間處理大文件。

3. 如果文件較大

a. 配置Web.Config 文件時，保證 maxRequestLength 時響應時間 executionTimeout 合理。具體的值主要依賴于數據大小，允許一次性上傳的最大數據為2 GB

b. 保證 maxAllowedContentLength 在requestFiltering部分配置下正確設置，默認值為30MB，最大值4GB

一旦完成預先配置，那么創建數據流服務就非常簡單了，首先 需要定義文件流“ApiController”，如下：

1: /// <summary> 2: /// File streaming API 3: /// </summary> 4: [RoutePrefix("filestreaming")] 5: [RequestModelValidator] 6: public class StreamFilesController : ApiController 7: { 8: /// <summary> 9: /// Get File meta data 10: /// </summary> 11: /// <param name="fileName">FileName value</param> 12: /// <returns>FileMeta data response.</returns> 13: [Route("getfilemetadata")] 14: public HttpResponseMessage GetFileMetaData(string fileName) 15: { 16: // ......................................... 17: // Full code available in the source control 18: // ......................................... 19: ? 20: } 21: ? 22: /// <summary> 23: /// Search file and return its meta data in all download directories 24: /// </summary> 25: /// <param name="fileName">FileName value</param> 26: /// <returns>List of file meta datas response</returns> 27: [HttpGet] 28: [Route("searchfileindownloaddirectory")] 29: public HttpResponseMessage SearchFileInDownloadDirectory(string fileName) 30: { 31: // ......................................... 32: // Full code available in the source control 33: // ......................................... 34: } 35: ? 36: /// <summary> 37: /// Asynchronous Download file 38: /// </summary> 39: /// <param name="fileName">FileName value</param> 40: /// <returns>Tasked File stream response</returns> 41: [Route("downloadasync")] 42: [HttpGet] 43: public async Task<HttpResponseMessage> DownloadFileAsync(string fileName) 44: { 45: // ......................................... 46: // Full code available in the source control 47: // ......................................... 48: } 49: ? 50: /// <summary> 51: /// Download file 52: /// </summary> 53: /// <param name="fileName">FileName value</param> 54: /// <returns>File stream response</returns> 55: [Route("download")] 56: [HttpGet] 57: public HttpResponseMessage DownloadFile(string fileName) 58: { 59: // ......................................... 60: // Full code available in the source control 61: // ......................................... 62: } 63: ? 64: /// <summary> 65: /// Upload file(s) 66: /// </summary> 67: /// <param name="overWrite">An indicator to overwrite a file if it exist in the server</param> 68: /// <returns>Message response</returns> 69: [Route("upload")] 70: [HttpPost] 71: public HttpResponseMessage UploadFile(bool overWrite) 72: { 73: // ......................................... 74: // Full code available in the source control 75: // ......................................... 76: } 77: ? 78: /// <summary> 79: /// Asynchronous Upload file 80: /// </summary> 81: /// <param name="overWrite">An indicator to overwrite a file if it exist in the server</param> 82: /// <returns>Tasked Message response</returns> 83: [Route("uploadasync")] 84: [HttpPost] 85: public async Task<HttpResponseMessage> UploadFileAsync(bool overWrite) 86: { 87: // ......................................... 88: // Full code available in the source control 89: // ......................................... 90: } 91: }

Download 服務方法首先需要確認請求的文件是否存在，如果未找到，則返回錯誤提示“file is not found”,如果找到此文件，內容則轉換為字節附加到響應對象，為“application/octet-stream” MIMI 內容類型。

1: /// <summary> 2: /// Download file 3: /// </summary> 4: /// <param name="fileName">FileName value<param> 5: /// <returns>File stream response<returns> 6: [Route("download")] 7: [HttpGet] 8: public HttpResponseMessage DownloadFile(string fileName) 9: { 10: HttpResponseMessage response = Request.CreateResponse(); 11: FileMetaData metaData = new FileMetaData(); 12: try 13: { 14: string filePath = Path.Combine(this.GetDownloadPath(), @"\", fileName); 15: FileInfo fileInfo = new FileInfo(filePath); 16: ? 17: if (!fileInfo.Exists) 18: { 19: metaData.FileResponseMessage.IsExists = false; 20: metaData.FileResponseMessage.Content = string.Format("{0} file is not found !", fileName); 21: response = Request.CreateResponse(HttpStatusCode.NotFound, metaData, new MediaTypeHeaderValue("text/json")); 22: } 23: else 24: { 25: response.Headers.AcceptRanges.Add("bytes"); 26: response.StatusCode = HttpStatusCode.OK; 27: response.Content = new StreamContent(fileInfo.ReadStream()); 28: response.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment"); 29: response.Content.Headers.ContentDisposition.FileName = fileName; 30: response.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream"); 31: response.Content.Headers.ContentLength = fileInfo.Length; 32: } 33: } 34: catch (Exception exception) 35: { 36: // Log exception and return gracefully 37: metaData = new FileMetaData(); 38: metaData.FileResponseMessage.Content = ProcessException(exception); 39: response = Request.CreateResponse(HttpStatusCode.InternalServerError, metaData, new MediaTypeHeaderValue("text/json")); 40: } 41: return response; 42: }

Upload服務方法則會在multipart/form-data MIMI 內容類型執行，首先會檢測HTTP 請求的內容類型是否是多主體，如果是，則對比內容長度是否超過最大尺寸，如果沒有超過，則開始上傳內容，當操作完成之后，則提示相應的信息。

代碼片段如下：

1: /// <summary> 2: /// Upload file(s) 3: /// </summary> 4: /// <param name="overWrite">An indicator to overwrite a file if it exist in the server.</param> 5: /// <returns>Message response</returns> 6: [Route("upload")] 7: [HttpPost] 8: public HttpResponseMessage UploadFile(bool overWrite) 9: { 10: HttpResponseMessage response = Request.CreateResponse(); 11: List<FileResponseMessage> fileResponseMessages = new List<FileResponseMessage>(); 12: FileResponseMessage fileResponseMessage = new FileResponseMessage { IsExists = false }; 13: ? 14: try 15: { 16: if (!Request.Content.IsMimeMultipartContent()) 17: { 18: fileResponseMessage.Content = "Upload data request is not valid !"; 19: fileResponseMessages.Add(fileResponseMessage); 20: response = Request.CreateResponse(HttpStatusCode.UnsupportedMediaType, fileResponseMessages, new MediaTypeHeaderValue("text/json")); 21: } 22: ? 23: else 24: { 25: response = ProcessUploadRequest(overWrite); 26: } 27: } 28: catch (Exception exception) 29: { 30: // Log exception and return gracefully 31: fileResponseMessage = new FileResponseMessage { IsExists = false }; 32: fileResponseMessage.Content = ProcessException(exception); 33: fileResponseMessages.Add(fileResponseMessage); 34: response = Request.CreateResponse(HttpStatusCode.InternalServerError, fileResponseMessages, new MediaTypeHeaderValue("text/json")); 35: ? 36: } 37: return response; 38: } 39: ? 40: /// <summary> 41: /// Asynchronous Upload file 42: /// </summary> 43: /// <param name="overWrite">An indicator to overwrite a file if it exist in the server.<param> 44: /// <returns>Tasked Message response</returns> 45: [Route("uploadasync")] 46: [HttpPost] 47: public async Task<HttpResponseMessage> UploadFileAsync(bool overWrite) 48: { 49: return await new TaskFactory().StartNew( 50: () => 51: { 52: return UploadFile(overWrite); 53: }); 54: } 55: ? 56: /// <summary> 57: /// Process upload request in the server 58: /// </summary> 59: /// <param name="overWrite">An indicator to overwrite a file if it exist in the server.</param> 60: /// </returns>List of message object</returns> 61: private HttpResponseMessage ProcessUploadRequest(bool overWrite) 62: { 63: // ......................................... 64: // Full code available in the source control 65: // ......................................... 66: }

調用download 及 upload 文件方法是控制臺應用，App 假定文件流服務通過HttpClient和相關類。基本下載文件代碼，創建下載HTTP 請求對象。

1: /// <summary> 2: /// Download file 3: /// </summary> 4: /// <returns>Awaitable Task object</returns> 5: private static async Task DownloadFile() 6: { 7: Console.ForegroundColor = ConsoleColor.Green; 8: Console.WriteLine("Please specify file name with extension and Press Enter :- "); 9: string fileName = Console.ReadLine(); 10: string localDownloadPath = string.Concat(@"c:\", fileName); // the path can be configurable 11: bool overWrite = true; 12: string actionURL = string.Concat("downloadasync?fileName=", fileName); 13: ? 14: try 15: { 16: Console.WriteLine(string.Format("Start downloading @ {0}, {1} time ", 17: DateTime.Now.ToLongDateString(), 18: DateTime.Now.ToLongTimeString())); 19: ? 20: ? 21: using (HttpClient httpClient = new HttpClient()) 22: { 23: httpClient.BaseAddress = baseStreamingURL; 24: HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Get, actionURL); 25: ? 26: await httpClient.SendAsync(request, HttpCompletionOption.ResponseHeadersRead). 27: ContinueWith((response) 28: => 29: { 30: Console.WriteLine(); 31: try 32: { 33: ProcessDownloadResponse(localDownloadPath, overWrite, response); 34: } 35: catch (AggregateException aggregateException) 36: { 37: Console.ForegroundColor = ConsoleColor.Red; 38: Console.WriteLine(string.Format("Exception : ", aggregateException)); 39: } 40: }); 41: } 42: } 43: catch (Exception ex) 44: { 45: Console.ForegroundColor = ConsoleColor.Red; 46: Console.WriteLine(ex.Message); 47: } 48: } 49: ? 50: ? 51: /// <summary> 52: /// Process download response object 53: /// </summary> 54: /// <param name="localDownloadFilePath">Local download file path</param> 55: /// <param name="overWrite">An indicator to overwrite a file if it exist in the client.</param> 56: /// <param name="response">Awaitable HttpResponseMessage task value</param> 57: private static void ProcessDownloadResponse(string localDownloadFilePath, bool overWrite, 58: Task<HttpResponseMessage> response) 59: { 60: if (response.Result.IsSuccessStatusCode) 61: { 62: response.Result.Content.DownloadFile(localDownloadFilePath, overWrite). 63: ContinueWith((downloadmessage) 64: => 65: { 66: Console.ForegroundColor = ConsoleColor.Green; 67: Console.WriteLine(downloadmessage.TryResult()); 68: }); 69: } 70: else 71: { 72: ProcessFailResponse(response); 73: } 74: }

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注意上述代碼中HttpClient 對象發送請求，并等待響應發送Header內容（HttpCompletionOption.ResponseHeadersRead ）。而不是發送全部的響應內容文件。一旦Response header 被讀，則執行驗證，一旦驗證成功，則執行下載方法。

以下代碼調用upload 文件流，與下載方法類似，創建多主體表單數據，并發送給服務器端。

1: /// <summary> 2: /// Upload file 3: /// </summary> 4: /// <returns>Awaitable task object</returns> 5: private static async Task UploadFile() 6: { 7: try 8: { 9: string uploadRequestURI = "uploadasync?overWrite=true"; 10: ? 11: MultipartFormDataContent formDataContent = new MultipartFormDataContent(); 12: ? 13: // Validate the file and add to MultipartFormDataContent object 14: formDataContent.AddUploadFile(@"c:\nophoto.png"); 15: formDataContent.AddUploadFile(@"c:\ReadMe.txt"); 16: ? 17: if (!formDataContent.HasContent()) // No files found to be uploaded 18: { 19: Console.ForegroundColor = ConsoleColor.Red; 20: Console.Write(formDataContent.GetUploadFileErrorMesage()); 21: return; 22: } 23: else 24: { 25: string uploadErrorMessage = formDataContent.GetUploadFileErrorMesage(); 26: if (!string.IsNullOrWhiteSpace(uploadErrorMessage)) // Some files couldn't be found 27: { 28: Console.ForegroundColor = ConsoleColor.Red; 29: Console.Write(uploadErrorMessage); 30: } 31: ? 32: HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Post, uploadRequestURI); 33: request.Content = formDataContent; 34: ? 35: using (HttpClient httpClient = new HttpClient()) 36: { 37: Console.ForegroundColor = ConsoleColor.Green; 38: Console.WriteLine(string.Format("Start uploading @ {0}, {1} time ", 39: DateTime.Now.ToLongDateString(), 40: DateTime.Now.ToLongTimeString())); 41: ? 42: httpClient.BaseAddress = baseStreamingURL; 43: await httpClient.SendAsync(request). 44: ContinueWith((response) 45: => 46: { 47: try 48: { 49: ProcessUploadResponse(response); 50: } 51: catch (AggregateException aggregateException) 52: { 53: Console.ForegroundColor = ConsoleColor.Red; 54: Console.WriteLine(string.Format("Exception : ", aggregateException)); 55: } 56: }); 57: } 58: } 59: } 60: catch (Exception ex) 61: { 62: Console.ForegroundColor = ConsoleColor.Red; 63: Console.WriteLine(ex.Message); 64: } 65: } 66: ? 67: /// <summary> 68: /// Process download response object 69: /// </summary> 70: /// <param name="response">Awaitable HttpResponseMessage task value</param> 71: private static void ProcessUploadResponse(Task<HttpResponseMessage> response) 72: { 73: if (response.Result.IsSuccessStatusCode) 74: { 75: string uploadMessage = string.Format("\nUpload completed @ {0}, {1} time ", 76: DateTime.Now.ToLongDateString(), 77: DateTime.Now.ToLongTimeString()); 78: Console.ForegroundColor = ConsoleColor.Green; 79: Console.WriteLine(string.Format("{0}\nUpload Message : \n{1}", uploadMessage, 80: JsonConvert.SerializeObject(response.Result.Content.ReadAsAsync<List<FileResponseMessage>>().TryResult(), Formatting.Indented))); 81: } 82: else 83: { 84: ProcessFailResponse(response); 85: } 86: }

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數據流項目由可擴展類和方法組成，本文就不再詳述。下篇文章中將介紹“使用HTTPS 開發項目”

數據流是數據傳輸中的重要部分，學習了本節內容有助于大家更好地進行ASP.NET的開發。當然，還可以借助一些開發工具來助力開發過程。ComponentOne Studio for ASP.NET?提供了一整套完備的開發工具包，用于在各種瀏覽器中創建和設計具有現代風格的Web應用程序。

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下載源代碼

原文鏈接：http://www.codeproject.com/Articles/838274/Web-API-Thoughts-of-Data-Streaming#Hist

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原文鏈接：http://www.cnblogs.com/powertoolsteam/p/5029475.html

轉載于:https://www.cnblogs.com/Percy_Lee/p/5662424.html

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