.NET Core第32天_Controller Action的各種不同回傳(FileContentResult,FileStreamResult,VirtualFileResult,PhysicalFileResult,JsonResult,EmptyResult,NoContentResult)_part2

 

FileContentResult

和FileResult不同點在於傳入參數要是binary型態

且結果不會下載而是直接呈現在網頁上

這裡準備預設./wwwroot/css/site.css和./Data/Products.xml兩種檔案

測試的action

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public FileContentResult DownloadContent_css() { var testFile = System.IO.File.ReadAllBytes("./wwwroot/css/site.css"); return new FileContentResult(testFile,"text/plain"); } public FileContentResult DownloadContent_xml() { var testFile = System.IO.File.ReadAllBytes("./Data/Products.xml"); return new FileContentResult(testFile, "text/xml"); }

效果

FileStreamResult

把文本內容透過stream形式寫入來做檔案下載

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public FileStreamResult CreateFile() { var stream = new System.IO.MemoryStream(System.Text.Encoding.ASCII.GetBytes("Hello FileStreamResult")); return new FileStreamResult(stream, new Microsoft.Net.Http.Headers.MediaTypeHeaderValue("text/plain")) { FileDownloadName = "test.txt" }; }

效果

VirtualFileResult 跟PhysicalFileResult

虛擬檔案路徑(相對路徑一定要存放wwwroot下的目錄)

跟

實際硬碟檔案路徑(要指定實際硬碟絕對路徑)

這裡我們注入IWebHostEnvironment 間接取得站台根目錄

測試程式

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using Microsoft.AspNetCore.Hosting; using Microsoft.AspNetCore.Mvc; using Microsoft.Extensions.Logging; using Net5AppDiffAction.Models; using System; using System.Collections.Generic; using System.Diagnostics; using System.Linq; using System.Threading.Tasks; namespace Net5AppDiffAction.Controllers { public class HomeController : Controller { private readonly ILogger<HomeController> _logger; private readonly IWebHostEnvironment _environment; public HomeController(ILogger<HomeController> logger, IWebHostEnvironment enviroment) { _logger = logger; _environment = enviroment; } public VirtualFileResult VirtualFileResultDemo() { return new VirtualFileResult("/css/site.css", "text/plain"); } public PhysicalFileResult ShowProducts() { return new PhysicalFileResult(_environment.ContentRootPath + "/Data/Products.xml", "text/xml"); } public PhysicalFileResult PhysicalFileResultDemo() { return new PhysicalFileResult(_environment.ContentRootPath + "/wwwroot/css/site.css", "text/plain"); } } }

效果

JsonResult

這裡準備創建好一個 model class Products

寫回傳Json result的 action

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public JsonResult ShowNewProducts() { Products prod = new Products() { ProductCode = 101, ProductName = "Printer", Cost = 1500 }; return Json(prod); }

藉由JsonResult序列化物件至JSON格式字串

運行效果

EmptyResult 和 NoContentResult

測試action

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public EmptyResult EmptyResultDemo() { return new EmptyResult(); } public NoContentResult NoContentResultDemo() { return NoContent(); }

各自差異在於

NoContentResult status code返回204

EmptyResult  status code則是預設的200返回

使用時機

當你不想有任何response顯示在網頁上的時候

而同時也不想throw 出error直接給client端的時候

就會看你是傾向告知user你查詢結果為空(NoContentResult)

或者執行過程有錯(EmptyResult)

若想驗證回傳的status code可以下載Fiddler來自行測試

Ref:

FileResult In ASP.NET Core MVC

https://www.c-sharpcorner.com/article/fileresult-in-asp-net-core-mvc2/

認識 ASP․NET Core 檔案提供者與透過 Web API 下載實體檔案

https://blog.miniasp.com/post/2019/12/08/Understanding-File-Providers-in-ASP-NET-Core-and-Download-Physical-File

File Providers in ASP.NET Core

https://docs.microsoft.com/en-us/aspnet/core/fundamentals/file-providers?view=aspnetcore-3.1&WT.mc_id=DT-MVP-4015686

ASP.NET Core MVC returning file using FileResult

https://geeksarray.com/blog/aspnet-core-mvc-returning-file-using-fileresult