c# - 如何正确写入从 Web API 接收的文件

Question

我尝试制作一个简单的 Web API 来从服务器接收文件。

这是服务器部分:

var result = new HttpResponseMessage(HttpStatusCode.OK);
var stream = new FileStream(itemPath, FileMode.Open, FileAccess.Read);
result.Content = new StreamContent(stream);
result.Content.Headers.ContentType = 
      new MediaTypeHeaderValue("application/octet-stream");
result.Content.Headers.ContentDisposition = 
      new ContentDispositionHeaderValue("attachment") { FileName = itemPath };
return result;

客户端部分:

var client = new HttpClient();
var responce = Task.Run(() => client.GetAsync(@"https://localhost:...")).Result;
var bytes = Task.Run(() => responce.Content.ReadAsByteArrayAsync()).Result;
var writer = 
  new BinaryWriter(new FileStream(fileName, FileMode.CreateNew, FileAccess.Write));
writer.Write(bytes);
writer.Close();

以及写入的文件内容:

{"version":{"major":1,"minor":1,"build":-1,"revision":-1,"majorRevision":-1,
"minorRevision":-1},"content":{"headers":[{"key":"Content-Type","value":["application/octet-stream"]},{"key":"Content-Disposition",
"value":["attachment; filename=\"=?utf-8?B?ZDpcTGlicmFyeVBhdGhc0J/QsNGH0LXQutC+XEV4YW1wbGUgR
DVcQ2QxN1xDTElQQlJEXE1haW5Gcm0ucGFz?=\""]}]},"statusCode":200,
"reasonPhrase":"OK","headers":[],"requestMessage":null,"isSuccessStatusCode":true}

我预计此文件将包含来自服务器本身的文件，但不包含描述它的 JSON。

我错过了什么？

Answer 1

响应的内容不应是 HttpResponseMessage 的 JSON 表示形式。

Asp.net Core Web API 像普通模型对象一样读取 HttpResponseMessage 类并将其序列化为 JSON。

重构服务器端代码以在 Controller 中使用建议的语法

public IActionResult MyAction(...) {
    //...
    var stream = new FileStream(itemPath, FileMode.Open, FileAccess.Read);
    return File(stream, "application/octet-stream", "desired file name here");
}

它返回一个IActionResult派生的FileStreamResult

在客户端，尝试避免阻塞调用，例如.Result。还不清楚为什么异步调用在已经可以等待的情况下被包装在 Task.Run 中。

始终保持代码异步

var client = new HttpClient();
var response = await client.GetAsync(@"https://localhost:..."); ;
var bytes = await response.Content.ReadAsByteArrayAsync();
var fileName = response.Content.Headers.ContentDisposition.FileName;
using (var stream = new FileStream(fileName, FileMode.CreateNew, FileAccess.Write)) {
    await stream.WriteAsync(bytes, 0, bytes.Length);
}

响应内容可以作为流读取并直接复制到文件流

var client = new HttpClient();
var response = await client.GetAsync(@"https://localhost:..."); ;
var stream = await response.Content.ReadAsStreamAsync();
var fileName = response.Content.Headers.ContentDisposition.FileName;
using (var fileStream = new FileStream(fileName, FileMode.CreateNew, FileAccess.Write)) {
    await stream.CopyToAsync(fileStream);
}