ASP.NET Core 使用 FileStream 将 FileResult 文件发送到浏览器后删除该文件

        FileStream 在向浏览器发送文件时节省了服务器内存和资源，但如果需要删除文件怎么办？本文介绍如何在发送文件后删除文件；用 C# 编写。

另请参阅：位图创建和下载

        使用FileStream向浏览器发送数据效率更高，因为文件是从驱动器复制到浏览器，而不是将其加载到服务器的内存中，然后复制到客户端。但如果文件下载到浏览器后需要删除怎么办？关键是“重写”类Dispose()的方法FileStream。

此代码与.NET Core 3.1、.NET 5、.NET 6、.NET 7 和.NET 8兼容。

以下是从基本 Web 应用程序修改后的 HomeController.cs 文件：

// HomeController.cs
using Microsoft.AspNetCore.Mvc;

namespace WebApplication1.Controllers
{
    internal class FileStreamDelete : FileStream
    {
        readonly string path;

        public FileStreamDelete(string path, FileMode mode) : base(path, mode) // NOTE: must create all the constructors needed first
        {
            this.path = path;
        }

        protected override void Dispose(bool disposing) // NOTE: override the Dispose() method to delete the file after all is said and done
        {
            base.Dispose(disposing);
            if (disposing)
            {
                if (System.IO.File.Exists(path))
                    System.IO.File.Delete(path);
            }
        }
    }

    public class HomeController : Controller
    {
        public async Task<IActionResult> Index(CancellationToken cancel)
        {
            // NOTE: the file that will be created, sent to the browser and then permanently deleted
            string filename = "temp.txt"; // NOTE: use System.Guid.NewGuid() to generate a unique file name

            // NOTE: create the text file
            await System.IO.File.AppendAllTextAsync(filename, "THIS IS A TEST. THIS IS A TEST. THIS IS A TEST. THIS IS A TEST. THIS IS A TEST. THIS IS A TEST. THIS IS A TEST. THIS IS A TEST. THIS IS A TEST. THIS IS A TEST. THIS IS A TEST. THIS IS A TEST. THIS IS A TEST. THIS IS A TEST.", cancel);

            // NOTE: send the text file to the browser and watch it be deleted upon completion of the copy operation

            return File(new FileStreamDelete(filename, FileMode.Open), System.Net.Mime.MediaTypeNames.Text.Plain, "downloaded-file.txt");
        }
    }
}

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