如何创建使用C＃和HttpClient的以下POST请求：

我需要为我的Web API服务这样的要求：

[ActionName("exist")]
[System.Web.Mvc.HttpPost]
public bool CheckIfUserExist([FromBody] string login)
{           
    bool result = _membershipProvider.CheckIfExist(login);
    return result;
}

Answer 1:

using System;
using System.Collections.Generic;
using System.Net.Http;

class Program
{
    static void Main(string[] args)
    {
        Task.Run(() => MainAsync());
        Console.ReadLine();
    }

    static async Task MainAsync()
    {
        using (var client = new HttpClient())
        {
            client.BaseAddress = new Uri("http://localhost:6740");
            var content = new FormUrlEncodedContent(new[]
            {
                new KeyValuePair<string, string>("", "login")
            });
            var result = await client.PostAsync("/api/Membership/exists", content);
            string resultContent = await result.Content.ReadAsStringAsync();
            Console.WriteLine(resultContent);
        }
    }
}

Answer 2:

下面是例如同步调用，但你可以很容易地通过使用的await同步更改为异步：

var pairs = new List<KeyValuePair<string, string>>
            {
                new KeyValuePair<string, string>("login", "abc")
            };

var content = new FormUrlEncodedContent(pairs);

var client = new HttpClient {BaseAddress = new Uri("http://localhost:6740")};

    // call sync
var response = client.PostAsync("/api/membership/exist", content).Result; 
if (response.IsSuccessStatusCode)
{
}

Answer 3:

有许多关于asp.net网站你的问题的文章。我希望它可以帮助你。

如何调用与ASP网的API

http://www.asp.net/web-api/overview/advanced/calling-a-web-api-from-a-net-client

这是一小部分从文章后段

下面的代码发送一个包含一个JSON格式的产品实例的POST请求：

// HTTP POST
var gizmo = new Product() { Name = "Gizmo", Price = 100, Category = "Widget" };
response = await client.PostAsJsonAsync("api/products", gizmo);
if (response.IsSuccessStatusCode)
{
    // Get the URI of the created resource.
    Uri gizmoUrl = response.Headers.Location;
}

Answer 4:

你可以做这样的事情

HttpWebRequest req = (HttpWebRequest)WebRequest.Create("http://localhost:6740/api/Membership/exist");

req.Method = "POST";
req.ContentType = "application/x-www-form-urlencoded";         
req.ContentLength = 6;

StreamWriter streamOut = new StreamWriter(req.GetRequestStream(), System.Text.Encoding.ASCII);
streamOut.Write(strRequest);
streamOut.Close();
StreamReader streamIn = new StreamReader(req.GetResponse().GetResponseStream());
string strResponse = streamIn.ReadToEnd();
streamIn.Close();

然后strReponse应该包含你的web服务返回的值

文章来源: .NET HttpClient. How to POST string value?