WebRequest是HttpWebRequest的抽象基类 – 您不能直接使用它。它是其他*请求类的基类(用于FTP，文件和其他类型的Web请求)。这些类都用于从Web获取资源(文件)。

还有一个WebClient类 – 可能是使用所有用于从Internet检索资源的BCL类最简单的类。

另一方面，HttpRequest表示ASP.NET应用程序中资源的请求 – 这是请求的服务器端。

主要的区别是HttpWebRequest是HTTP客户端，HttpRequest是在ASP.NET Web应用程序中使用的服务器端。

public static string Post(string Url,string postDataStr,string cookies)
        {
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Url);
            request.Method = "POST";
            if (cookies != null)
                request.Headers.Add("Cookie",cookies);
            request.ContentType = "application/x-www-form-urlencoded";
            request.ContentLength = postDataStr.Length;
            StreamWriter writer = new StreamWriter(request.GetRequestStream(),Encoding.ASCII);
            writer.Write(postDataStr);
            writer.Close();
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            string encoding = response.ContentEncoding;
            if (encoding == null || encoding.Length < 1)
            {
                encoding = "UTF-8"; //默认编码  
            }
            StreamReader reader = new StreamReader(response.GetResponseStream(),Encoding.GetEncoding(encoding));
            string retString = reader.ReadToEnd();
            return retString;
        }

        public static string Get(string Url,string cookies)
        {
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Url);
            request.Method = "GET";
            if (cookies != null)
                request.Headers.Add("Cookie",cookies);
            request.ContentType = "application/x-www-form-urlencoded";
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            string encoding = response.ContentEncoding;
            if (encoding == null || encoding.Length < 1)
            {
                encoding = "UTF-8"; //默认编码  
            }
            StreamReader reader = new StreamReader(response.GetResponseStream(),Encoding.GetEncoding(encoding));
            string retString = reader.ReadToEnd();
            return retString;
        }

public HttpResponseMessage Post([FromUri]string machineName)
    {
        HttpResponseMessage result = null;
        var httpRequest = HttpContext.Current.Request;

        if (httpRequest.Files.Count > 0 && !String.IsNullOrEmpty(machineName))
        ...

客户端：

public static void PostFile(string url,string filePath)
    {
        if (String.IsNullOrWhiteSpace(url) || String.IsNullOrWhiteSpace(filePath))
            throw new ArgumentNullException();

        if (!File.Exists(filePath))
            throw new FileNotFoundException();

        using (var handler = new httpclienthandler { Credentials=  new NetworkCredential(AppData.UserName,AppData.Password,AppCore.Domain) })
        using (var client = new HttpClient(handler))
        using (var content = new MultipartFormDataContent())
        using (var ms = new MemoryStream(File.ReadAllBytes(filePath)))
        {
            var fileContent = new StreamContent(ms);
            fileContent.Headers.Contentdisposition = new ContentdispositionHeaderValue("attachment")
            {
                FileName = Path.GetFileName(filePath)
            };
            content.Add(fileContent);
            content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");

            var result = client.PostAsync(url,content).Result;
            result.EnsureSuccessstatusCode();
        }
    }

在服务器端,httpRequest.Files集合始终为空.但标题(内容长度等)是正确的.

public class UploadController : ApiController 
{ 
    public async Task<HttpResponseMessage> PostFile() 
    { 
        // Check if the request contains multipart/form-data. 
        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) 
            { 
                FileInfo fileInfo = new FileInfo(file.LocalFileName); 
                sb.Append(string.Format("Uploaded file: {0} ({1} bytes)\n",fileInfo.Name,fileInfo.Length)); 
            } 
            return new HttpResponseMessage() 
            { 
                Content = new StringContent(sb.ToString()) 
            }; 
        } 
        catch (System.Exception e) 
        { 
            return Request.CreateErrorResponse(HttpStatusCode.InternalServerError,e); 
        } 
    } 

}