在 ASP.Net Core Web API 中返回文件 [英] Return file in ASP.Net Core Web API

问题描述

我想在我的 ASP.Net Web API 控制器中返回一个文件，但我所有的方法都将 HttpResponseMessage 作为 JSON 返回.

I want to return a file in my ASP.Net Web API Controller, but all my approaches return the HttpResponseMessage as JSON.

public async Task<HttpResponseMessage> DownloadAsync(string id)
{
    var response = new HttpResponseMessage(HttpStatusCode.OK);
    response.Content = new StreamContent({{__insert_stream_here__}});
    response.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
    return response;
}

当我在浏览器中调用此端点时，Web API 将 HttpResponseMessage 作为 JSON 返回，并将 HTTP 内容标头设置为 application/json.

When I call this endpoint in my browser, the Web API returns the HttpResponseMessage as JSON with the HTTP Content Header set to application/json.

推荐答案

如果这是 ASP.net-Core，那么您正在混合 Web API 版本.让操作返回派生的 IActionResult，因为在您当前的代码中，框架将 HttpResponseMessage 视为模型.

If this is ASP.net-Core then you are mixing web API versions. Have the action return a derived IActionResult because in your current code the framework is treating HttpResponseMessage as a model.

[Route("api/[controller]")]
public class DownloadController : Controller {
    //GET api/download/12345abc
    [HttpGet("{id}")]
    public async Task<IActionResult> Download(string id) {
        Stream stream = await {{__get_stream_based_on_id_here__}}

        if(stream == null)
            return NotFound(); // returns a NotFoundResult with Status404NotFound response.

        return File(stream, "application/octet-stream"); // returns a FileStreamResult
    }    
}

注意:

当响应完成时，框架将处理在这种情况下使用的流.如果使用 using 语句，流将在响应发送之前被释放，并导致异常或损坏响应.

The framework will dispose of the stream used in this case when the response is completed. If a using statement is used, the stream will be disposed before the response has been sent and result in an exception or corrupt response.

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