咨询区
Hooch：
我会用 GET Request，但如何使用 Post Request 还得请教大家。
回答区
Evan Mulawski：
有多种方式可以使用 Http 的 GET 和 Post 请求。
A方法：HttpClient (推荐)
HttpClient 可用于 .NET Framework 4.5+, .NET Standard 1.1+,.NET Core 1.0+，当前是最值得推荐的方式，它支持异步并且高性能，如果你是非常老的平台，还得需要从 Nuget 上安装一下 System.Net.Http。
HttpClient 推荐的做法就是在应用程序生命周期内初始化一次，除非你有特殊的理由不这么做，使用方法如下：
private static readonly HttpClient client = new HttpClient();POST 方式
var values = new Dictionary<string, string>
{{ "thing1", "hello" },{ "thing2", "world" }
};var content = new FormUrlEncodedContent(values);var response = await client.PostAsync("http://www.example.com/recepticle.aspx", content);var responseString = await response.Content.ReadAsStringAsync();GET
var responseString = await client.GetStringAsync("http://www.example.com/recepticle.aspx");B方法：第三方包
RestSharp
POST
var client = new RestClient("http://example.com");// client.Authenticator = new HttpBasicAuthenticator(username, password);var request = new RestRequest("resource/{id}");request.AddParameter("thing1", "Hello");request.AddParameter("thing2", "world");request.AddHeader("header", "value");request.AddFile("file", path);var response = client.Post(request);var content = response.Content; // Raw content as stringvar response2 = client.Post<Person>(request);var name = response2.Data.Name;Flurl.Http
这是一个比较新的工具包，拥有便捷易用的 API 接口，底层使用的是 HttpClient，而且支持移植，可以在 Nuget 上获取。
POST
var responseString = await "http://www.example.com/recepticle.aspx".PostUrlEncodedAsync(new { thing1 = "hello", thing2 = "world" }).ReceiveString();GET
var responseString = await "http://www.example.com/recepticle.aspx".GetStringAsync();C方法：HttpWebRequest (不推荐)
它可用于 .NET Framework 1.1+, .NET Standard 2.0+,.NET Core 1.0+，在 .netcore 中仅仅是为了兼容而存在的，它封装了 HttpClient，性能较差，也没有提供什么新功能。
POST
var request = (HttpWebRequest)WebRequest.Create("http://www.example.com/recepticle.aspx");var postData = "thing1=" + Uri.EscapeDataString("hello");postData += "&thing2=" + Uri.EscapeDataString("world");
var data = Encoding.ASCII.GetBytes(postData);request.Method = "POST";
request.ContentType = "application/x-www-form-urlencoded";
request.ContentLength = data.Length;using (var stream = request.GetRequestStream())
{stream.Write(data, 0, data.Length);
}var response = (HttpWebResponse)request.GetResponse();var responseString = new StreamReader(response.GetResponseStream()).ReadToEnd();GET
var request = (HttpWebRequest)WebRequest.Create("http://www.example.com/recepticle.aspx");var response = (HttpWebResponse)request.GetResponse();var responseString = new StreamReader(response.GetResponseStream()).ReadToEnd();D方法：WebClient (不推荐)
WebClient 封装了 HttpWebRequest，在 .NET Framework 1.1+,NET Standard 2.0+,.NET Core 2.0+ 中可用。
POST
using (var client = new WebClient())
{var values = new NameValueCollection();values["thing1"] = "hello";values["thing2"] = "world";var response = client.UploadValues("http://www.example.com/recepticle.aspx", values);var responseString = Encoding.Default.GetString(response);
}GET
using (var client = new WebClient())
{var responseString = client.DownloadString("http://www.example.com/recepticle.aspx");
}点评区
Evan Mulawski 大佬提到了 5 种方式，非常全面，值得学习了解，有一点要注意，在 .net core 2.1 种提供了一个新的 HttpClientFacotry 类，就就是用来解决 HttpClient 的各种不足，有兴趣可以看下 MSDN：https://docs.microsoft.com/en-us/dotnet/architecture/microservices/implement-resilient-applications/use-httpclientfactory-to-implement-resilient-http-requests#what-is-httpclientfactory
原文链接：https://stackoverflow.com/questions/4015324/how-to-make-an-http-post-web-request
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