如何从 C# 中的控制台应用程序通过 http 发送文件？

试试这样：

using (var client = new HttpClient())
using (var formData = new MultipartFormDataContent())
using (var fileStream = File.OpenRead(localPath))
{
    HttpContent fileStreamContent = new StreamContent(fileStream);

    var filename = Path.GetFileName(localPath);

    // эмулируем <input type="file" name="upload"/>
    formData.Add(fileStreamContent, "upload");

    // эмулируем (action="{url}" method="post")
    var response = await client.PostAsync(url, formData);

    // и т. д.
}

借来这里。

如果你真的，真的不想要异步代码，你也可以进行阻塞调用（但我不推荐）：

    var response = client.PostAsync(url, formData).Result;

文件以编码方式传输multipart/form-data。因此，您需要：

1. 生成分隔符（例如，Asrf456BGe4h）

2. 提交标题

   Content-Type: multipart/form-data; boundary=Asrf456BGe4h
   

3. 发送请求正文：

   (отсутствующая преамбула)
   --Asrf456BGe4h
   Content-Disposition: form-data; name="AttachedFile1"; filename="horror-photo-1.jpg"
   Content-Type: image/jpeg
   (пустая строка)
   (двоичное содержимое первой фотографии)
   --Asrf456BGe4h--
   (отсутствующий эпилог - пустая строка)
   

   注意末尾的两个连字符。

然后我似乎为了一件事情绞尽脑汁好几个小时

1. 安装提琴手
2. 您通过浏览器发送文件，一切正常。
3. 你看看提琴手究竟发生了什么。
4. 提交您的代码。你看看提琴手发生了什么。
5. 您完成您的代码，直到第 4 步中发送的内容与第 3 步中发送的内容匹配。

它看起来像这样：
将文件写入流：

var file = File.ReadAllBytes(filename); 
var req = WebRequest.CreateHttp(url); //url - адрес сервера
req.Method = WebRequestMethods.Http.Post;
//Отправляете на сервер(думаю знаете как)

采用字节流的操作必须具有 byte[] 参数
此处描述了如何将字节流写入文件：
https ://stackoverflow.com/questions/6397235/write-bytes-to-file

有一次我用 1C 写了一篇 .Net 文章。异步 HTTP 请求，Post 多个 multipart/form-data 文件，使用 gzip、deflate 进行流量压缩，方便的站点解析等。

没错，1C 上有一个例子，但这不是特别重要

     public async Task  SendPostFile(string urlserviceapiSent)
    {
        using (var client = new System.Net.Http.HttpClient())
        using (var content = new System.Net.Http.MultipartFormDataContent())
        {
            client.BaseAddress = new System.Uri(urlserviceapiSent);
            var values = new System.Collections.Generic.Dictionary<String, String>()
                               {
                                   { "Name", "name"},
                                   { "id", "id"}
                                };

            //      content.Add(new FormUrlEncodedContent(values));
            foreach (var keyValuePair in values)
            {
                content.Add(new System.Net.Http.StringContent(keyValuePair.Value), keyValuePair.Key);
            }

            string fileName = @"C:/ТестXML";
            var fileContent = new System.Net.Http.StreamContent(System.IO.File.OpenRead(fileName));
            fileContent.Headers.ContentDisposition = new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment")
            {
                FileName = System.IO.Path.GetFileName(fileName)
            };
            content.Add(fileContent);

            // Вариант отправки двоичных данных из файла но более краткий
            var fileContent2 = new System.Net.Http.StreamContent(System.IO.File.OpenRead(fileName));
            content.Add(fileContent2, "attachment", "TestXml");



            var stringContent = new System.Net.Http.ByteArrayContent(Encoding.UTF8.GetBytes("Тестовая строка"));
            stringContent.Headers.ContentDisposition = new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment")
            {
                FileName = "Строка"
            };
            content.Add(stringContent);

            var requestUri = "api/values/SendFiles";

            var result = await client.PostAsync(requestUri, content);
            var str = await result.Content.ReadAsStringAsync();
            textBox.AppendText(str + Environment.NewLine);

        }
    }

诸如此类的问题

// 这是发送请求的样子 //POST http://localhost:40320/api/values/SendFiles HTTP/1.1 //Content-Type: multipart/form-data; boundary="9f2d525a-7383-46ab-8fc7-419d73486c02" //Host: localhost:40320 //Content-Length: 811 //Expect: 100-continue //Connection: Keep-Alive

//--9f2d525a-7383-46ab-8fc7-419d73486c02 //Content-Type: text/plain; charset=utf-8 //Content-Disposition: form-data; 名字=名字

//名称 //--9f2d525a-7383-46ab-8fc7-419d73486c02 //Content-Type: text/plain; charset=utf-8 //Content-Disposition: form-data; 名称=编号

//id //--9f2d525a-7383-46ab-8fc7-419d73486c02 //Content-Disposition: form-data; filename="=?utf-8?B?0J/RgNC+0YHRgtC+0KHRgtGA0L7QutCw?="; name=attachment //内容类型：文本/纯文本

//测试字符串 //--9f2d525a-7383-46ab-8fc7-419d73486c02 //Content-Disposition: form-data; filename="=?utf-8?B?0KLQtdGB0YJYTUw=?=" //Content-Type: application/octet-stream

//12345 //--9f2d525a-7383-46ab-8fc7-419d73486c02 //Content-Disposition: form-data; 名称=附件；文件名=TestXml；文件名*=utf-8''TestXml

//12345 //--9f2d525a-7383-46ab-8fc7-419d73486c02--

还有一个指向该服务的链接http://pastebin.com/1kyhAdai

[NonAction]
        string fileName(MultipartFileData fileData)
        {
            string fileName = fileData.Headers.ContentDisposition.FileName;

            if (string.IsNullOrEmpty(fileName))
            {
                return "";
            }

            if (fileName.StartsWith("\"") && fileName.EndsWith("\""))
            {
                fileName = fileName.Trim('"');
            }
            if (fileName.Contains(@"/") || fileName.Contains(@"\"))
            {
                fileName = Path.GetFileName(fileName);
            }

            return fileName;
        }
        [HttpPost]
        public async Task<HttpResponseMessage> SendFiles()
        {
            if (!Request.Content.IsMimeMultipartContent())
            {
                throw new HttpResponseException(HttpStatusCode.UnsupportedMediaType);
            }

            string root = HttpContext.Current.Server.MapPath("~/App_Data");
            var provider = new MultipartFormDataStreamProvider(root);

            try
            {
                StringBuilder sb = new StringBuilder(); // Holds the response body

                // Read the form data and return an async task.
                await Request.Content.ReadAsMultipartAsync(provider);

                // This illustrates how to get the form data.
                foreach (var key in provider.FormData.AllKeys)
                {
                    foreach (var val in provider.FormData.GetValues(key))
                    {
                        sb.Append(string.Format("{0}: {1}\n", key, val));
                    }
                }

                // This illustrates how to get the file names for uploaded files.
                foreach (var file in provider.FileData)
                {
                    var fileInfo = new FileInfo(file.LocalFileName);
                    sb.Append(string.Format("Uploaded file: {0} {1} ({2} bytes)\n", fileName(file), fileInfo.Name, fileInfo.Length));
                }
                return new HttpResponseMessage()
                {
                    Content = new StringContent(sb.ToString())
                };
            }
            catch (System.Exception e)
            {
                return Request.CreateErrorResponse(HttpStatusCode.InternalServerError, e);
            }


        }