public ActionResult Download()
{
    var document = ...
    var cd = new System.Net.Mime.ContentDisposition
    {
        // for example foo.bak
        FileName = document.FileName, 

        // always prompt the user for downloading, set to true if you want 
        // the browser to try to show the file inline
        Inline = false, 
    };
    Response.AppendHeader("Content-Disposition", cd.ToString());
    return File(document.Data, document.ContentType);
}

注意:上面的示例代码不能正确地说明文件名中的国际字符。相关标准化参见RFC6266。我相信ASP的最新版本。Net MVC的File()方法和ContentDispositionHeaderValue类很好地解释了这一点。——奥斯卡2016-02-25

我相信这个答案更清晰，(基于…… https://stackoverflow.com/a/3007668/550975)

    public ActionResult GetAttachment(long id)
    {
        FileAttachment attachment;
        using (var db = new TheContext())
        {
            attachment = db.FileAttachments.FirstOrDefault(x => x.Id == id);
        }

        return File(attachment.FileData, "application/force-download", Path.GetFileName(attachment.FileName));
    }

FileVirtualPath—> Research\Global Office Review.pdf

public virtual ActionResult GetFile()
{
    return File(FileVirtualPath, "application/force-download", Path.GetFileName(FileVirtualPath));
}

由于“文档”变量上没有类型提示，我在接受的答案上遇到了麻烦:var document =…所以我把对我有用的作为替代，以防其他人遇到麻烦。

public ActionResult DownloadFile()
{
    string filename = "File.pdf";
    string filepath = AppDomain.CurrentDomain.BaseDirectory + "/Path/To/File/" + filename;
    byte[] filedata = System.IO.File.ReadAllBytes(filepath);
    string contentType = MimeMapping.GetMimeMapping(filepath);

    var cd = new System.Net.Mime.ContentDisposition
    {
        FileName = filename,
        Inline = true,
    };

    Response.AppendHeader("Content-Disposition", cd.ToString());

    return File(filedata, contentType);
}

Darin Dimitrov的答案是正确的。补充一点:

响应。AppendHeader(“附加”,cd.ToString ());可能会导致浏览器无法呈现文件，如果你的响应已经包含一个“Content-Disposition”头。在这种情况下，你可能想使用:

Response.Headers.Add("Content-Disposition", cd.ToString());

查看文件(例如txt):

return File("~/TextFileInRootDir.txt", MediaTypeNames.Text.Plain);

下载文件(例如txt):

return File("~/TextFileInRootDir.txt", MediaTypeNames.Text.Plain, "TextFile.txt");

注意:要下载文件，我们应该传递fileDownloadName参数

下面的代码为我从API服务中获取pdf文件并将其响应到浏览器-希望它有帮助;

public async Task<FileResult> PrintPdfStatements(string fileName)
    {
         var fileContent = await GetFileStreamAsync(fileName);
         var fileContentBytes = ((MemoryStream)fileContent).ToArray();
         return File(fileContentBytes, System.Net.Mime.MediaTypeNames.Application.Pdf);
    }

Action方法需要用流、字节[]或文件的虚拟路径返回FileResult。您还需要知道正在下载的文件的内容类型。下面是一个示例(快速/肮脏)实用方法。视频链接示例 如何使用asp.net core下载文件

[Route("api/[controller]")]
public class DownloadController : Controller
{
    [HttpGet]
    public async Task<IActionResult> Download()
    {
        var path = @"C:\Vetrivel\winforms.png";
        var memory = new MemoryStream();
        using (var stream = new FileStream(path, FileMode.Open))
        {
            await stream.CopyToAsync(memory);
        }
        memory.Position = 0;
        var ext = Path.GetExtension(path).ToLowerInvariant();
        return File(memory, GetMimeTypes()[ext], Path.GetFileName(path));
    }

    private Dictionary<string, string> GetMimeTypes()
    {
        return new Dictionary<string, string>
        {
            {".txt", "text/plain"},
            {".pdf", "application/pdf"},
            {".doc", "application/vnd.ms-word"},
            {".docx", "application/vnd.ms-word"},
            {".png", "image/png"},
            {".jpg", "image/jpeg"},
            ...
        };
    }
}

如果你像我一样，在学习Blazor时通过Razor组件来了解这个主题，那么你会发现你需要更多地跳出框框来解决这个问题。如果(也像我一样)Blazor是你第一次尝试mvc类型的世界，那么它就有点雷区，因为它的文档对于这种“卑微”的任务并没有多大帮助。

因此，在撰写本文时，如果不嵌入MVC控制器来处理文件下载部分，您就无法使用vanilla Blazor/Razor实现这一点，示例如下:

using Microsoft.AspNetCore.Mvc;
using Microsoft.Net.Http.Headers;

[Route("api/[controller]")]
[ApiController]
public class FileHandlingController : ControllerBase
{
    [HttpGet]
    public FileContentResult Download(int attachmentId)
    {
        TaskAttachment taskFile = null;

        if (attachmentId > 0)
        {
            // taskFile = <your code to get the file>
            // which assumes it's an object with relevant properties as required below

            if (taskFile != null)
            {
                var cd = new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment")
                {
                    FileNameStar = taskFile.Filename
                };

                Response.Headers.Add(HeaderNames.ContentDisposition, cd.ToString());
            }
        }

        return new FileContentResult(taskFile?.FileData, taskFile?.FileContentType);
    }
}

接下来，确保您的应用程序启动(startup .cs)配置为正确使用MVC，并有以下行(如果没有，则添加它):

        services.AddMvc();

. .然后最后修改你的组件以链接到控制器，例如(使用自定义类的迭代示例):

    <tbody>
        @foreach (var attachment in yourAttachments)
        {
        <tr>
            <td><a href="api/FileHandling?attachmentId=@attachment.TaskAttachmentId" target="_blank">@attachment.Filename</a> </td>
            <td>@attachment.CreatedUser</td>
            <td>@attachment.Created?.ToString("dd MMM yyyy")</td>
            <td><ul><li class="oi oi-circle-x delete-attachment"></li></ul></td>
        </tr>
        }
        </tbody>

希望这能帮助那些挣扎的人(像我一样!)，在Blazor的领域里得到这个看似简单的问题的适当答案…!