.NET Framework 4.5中的System.Net.Http.HttpClient和System.Net.Http.HttpClientHandler实现了IDisposable(通过System.Net.Http.HttpMessageInvoker).

该using声明文件说:

通常,当您使用IDisposable对象时,您应该在using语句中声明并实例化它.

这个答案使用了这种模式:

var baseAddress = new Uri("http://example.com");
var cookieContainer = new CookieContainer();
using (var handler = new HttpClientHandler() { CookieContainer = cookieContainer })
using (var client = new HttpClient(handler) { BaseAddress = baseAddress })
{
    var content = new FormUrlEncodedContent(new[]
    {
        new KeyValuePair<string, string>("foo", "bar"),
        new KeyValuePair<string, string>("baz", "bazinga"),
    });
    cookieContainer.Add(baseAddress, new Cookie("CookieName", "cookie_value"));
    var result = client.PostAsync("/test", content).Result;
    result.EnsureSuccessStatusCode();
}

但是微软最明显的例子并没有Dispose()明确地或隐含地调用.例如:

• 在原来的博客文章中宣布的HttpClient的RELASE. …

编辑: 这个问题看起来可能是同一个问题,但没有回复......

编辑:在测试用例5中,任务似乎陷入WaitingForActivation状态.

我在.NET 4.5中使用System.Net.Http.HttpClient遇到了一些奇怪的行为 - 其中"等待"调用(例如)的结果httpClient.GetAsync(...)将永远不会返回.

只有在使用新的async/await语言功能和Tasks API时才会出现这种情况 - 在仅使用continuation时,代码似乎始终有效.

下面是一些重现问题的代码 - 将其放入Visual Studio 11中新的"MVC 4 WebApi项目"中,以显示以下GET端点:

/api/test1
/api/test2
/api/test3
/api/test4
/api/test5 <--- never completes
/api/test6

这里的每个端点都返回相同的数据(来自stackoverflow.com的响应头),除非/api/test5从未完成.

我在HttpClient类中遇到过错误,还是以某种方式滥用了API？

代码重现:

public class BaseApiController : ApiController
{
    /// <summary>
    /// Retrieves data using continuations
    /// </summary>
    protected Task<string> Continuations_GetSomeDataAsync()
    {
        var httpClient = new HttpClient();

        var t = httpClient.GetAsync("http://stackoverflow.com", HttpCompletionOption.ResponseHeadersRead);

        return t.ContinueWith(t1 => t1.Result.Content.Headers.ToString());
    }

    /// <summary>
    /// Retrieves data using async/await
    /// …

请考虑以下代码,其中BaseAddress定义了部分URI路径.

using (var handler = new HttpClientHandler())
using (var client = new HttpClient(handler))
{
    client.BaseAddress = new Uri("http://something.com/api");
    var response = await client.GetAsync("/resource/7");
}

我希望这可以执行GET请求http://something.com/api/resource/7.但事实并非如此.

经过一番搜索,我发现这个问题和答案:HttpClient with BaseAddress.建议是/放在最后BaseAddress.

using (var handler = new HttpClientHandler())
using (var client = new HttpClient(handler))
{
    client.BaseAddress = new Uri("http://something.com/api/");
    var response = await client.GetAsync("/resource/7");
}

它仍然无法正常工作.这是文档:HttpClient.BaseAddress这里发生了什么？

public static async Task<string> GetData(string url, string data)
{
    UriBuilder fullUri = new UriBuilder(url);

    if (!string.IsNullOrEmpty(data))
        fullUri.Query = data;

    HttpClient client = new HttpClient();

    HttpResponseMessage response = await client.PostAsync(new Uri(url), /*expects HttpContent*/);

    response.Content.Headers.ContentType = new MediaTypeHeaderValue("application/json");
    response.EnsureSuccessStatusCode();
    string responseBody = await response.Content.ReadAsStringAsync();

    return responseBody;
}

将PostAsync采取一个需要另一个参数HttpContent.

我该如何设置HttpContent？任何适用于Windows Phone 8的文档都没有.

如果我这样做GetAsync,那就太棒了!但它需要POST的内容为key ="bla",某事="yay"

//编辑

非常感谢答案......这很有效,但这里还有一些不确定的地方:

    public static async Task<string> GetData(string url, string data)
    {
        data = "test=something";

        HttpClient client = new HttpClient();
        StringContent queryString …

我试图从我的web应用程序调用web api.使用.net 4.5并在编写代码时我收到错误HttpClient不包含定义PostAsJsonAsync方法

HttpClient client = new HttpClient();
client.BaseAddress = new Uri("http://localhost:51093/");
client.DefaultRequestHeaders.Accept.Add(
   new MediaTypeWithQualityHeaderValue("application/json"));
var user = new Users();
user.AgentCode = 100;
user.Remarks = "Test";
user.CollectionDate = System.DateTime.Today;
user.RemittanceDate = System.DateTime.Today;
user.TotalAmount = 1000;
user.OrgBranchID = 101;

var response = client.PostAsJsonAsync("api/AgentCollection", user).Result;

我收到错误消息:

HttpClient client = new HttpClient();
client.BaseAddress = new Uri("http://localhost:51093/");
client.DefaultRequestHeaders.Accept.Add(
   new MediaTypeWithQualityHeaderValue("application/json"));
var user = new Users();
user.AgentCode = 100;
user.Remarks = "Test";
user.CollectionDate = System.DateTime.Today;
user.RemittanceDate = System.DateTime.Today;
user.TotalAmount = 1000;
user.OrgBranchID = 101;

var …

我们的网络应用程序在.Net Framework 4.0中运行.UI通过ajax调用调用控制器方法.

我们需要从供应商处使用REST服务.我正在评估在.Net 4.0中调用REST服务的最佳方法.REST服务需要基本身份验证方案,它可以返回XML和JSON中的数据.没有要求上传/下载大量数据,我将来也看不到任何东西.我看了几个用于REST消费的开源代码项目,并没有找到任何值来证明项目中的额外依赖性.开始评估WebClient和HttpClient.我从NuGet下载了用于.Net 4.0的HttpClient.

我搜索了WebClient和之间的差异,HttpClient并且该网站提到单个HttpClient可以处理并发调用,它可以重用已解析的DNS,cookie配置和身份验证.我还没有看到由于差异我们可能获得的实用价值.

我做了一个快速的性能测试,以找到WebClient(同步调用),HttpClient(同步和异步)如何执行.以下是结果:

HttpClient对所有请求使用相同的实例(min - max)

WebClient同步:8毫秒 - 167毫秒
HttpClient同步:3毫秒 - 7228毫秒
HttpClient异步:985 - 10405毫秒

HttpClient为每个请求使用new (min - max)

WebClient同步:4毫秒 - 297毫秒
HttpClient同步:3毫秒 - 7953毫秒
HttpClient异步:1027 - 10834毫秒

码

public class AHNData
{
    public int i;
    public string str;
}

public class Program
{
    public static HttpClient httpClient = new HttpClient();
    private static readonly string _url = "http://localhost:9000/api/values/";

    public …

我正在构建一个类API来与API进行交互.我需要调用API并处理XML响应.我可以看到HttpClient用于异步连接的好处,但我正在做的是纯粹的同步,所以我看不到使用它的任何重大好处HttpWebRequest.

如果有人可以放弃任何光线,我将非常感激.我不是为了它而使用新技术的人.

当有一个或两个任务时它可以正常工作但是当我们列出了多个任务时会抛出错误"任务被取消".

List<Task> allTasks = new List<Task>();
allTasks.Add(....);
allTasks.Add(....);
Task.WaitAll(allTasks.ToArray(), configuration.CancellationToken);


private static Task<T> HttpClientSendAsync<T>(string url, object data, HttpMethod method, string contentType, CancellationToken token)
{
    HttpRequestMessage httpRequestMessage = new HttpRequestMessage(method, url);
    HttpClient httpClient = new HttpClient();
    httpClient.Timeout = new TimeSpan(Constants.TimeOut);

    if (data != null)
    {
        byte[] byteArray = Encoding.ASCII.GetBytes(Helper.ToJSON(data));
        MemoryStream memoryStream = new MemoryStream(byteArray);
        httpRequestMessage.Content = new StringContent(new StreamReader(memoryStream).ReadToEnd(), Encoding.UTF8, contentType);
    }

    return httpClient.SendAsync(httpRequestMessage).ContinueWith(task =>
    {
        var response = task.Result;
        return response.Content.ReadAsStringAsync().ContinueWith(stringTask =>
        {
            var json = stringTask.Result;
            return Helper.FromJSON<T>(json);
        }); …

如何使用C#和HttpClient创建以下POST请求:

我需要这样的WEB API服务请求:

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

HttpClientWebAPI客户端的生命周期应该是多少？为多个调用
设置一个实例是否更好HttpClient？

创建和处理HttpClient每个请求的开销是多少,如下面的示例所示(摘自http://www.asp.net/web-api/overview/web-api-clients/calling-a-web-api-from- a-net-client):

using (var client = new HttpClient())
{
    client.BaseAddress = new Uri("http://localhost:9000/");
    client.DefaultRequestHeaders.Accept.Clear();
    client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

    // New code:
    HttpResponseMessage response = await client.GetAsync("api/products/1");
    if (response.IsSuccessStatusCode)
    {
        Product product = await response.Content.ReadAsAsync<Product>();
        Console.WriteLine("{0}\t${1}\t{2}", product.Name, product.Price, product.Category);
    }
}