HttpClient - 发送请求答案

【问题标题】：HttpClient - sending a requestHttpClient - 发送请求
【发布时间】：2018-02-18 10:26:49
【问题描述】：

我正在尝试从我的 Dynamics CRM 在线发出 HttpRequest 以在外部 ERP 系统上创建记录。我使用 HttpClient 但我不确定我是否正确执行，我没有得到任何响应。代码如下：

 public async void Execute(){
        string query1 = $"<RequestData>" +
        $"<firstField>{model.firstField}</firstField>" +
        $"<secondField>{model.secondField}</secondField>" +
        $"<thirdField>{model.thirdField}</thirdField>" +
            $"</RequestData>";
       HttpClient client = CreateClient();
       HttpResponseMessage response = await SendRequest(client, HttpMethod.Put, query);
}

  private HttpClient CreateClient()
    {
        using (HttpClient client = new HttpClient())
        {
            client.BaseAddress = baseAdress;
            client.DefaultRequestHeaders.Accept.Clear();
            client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
            return client;
        }
    }

     private async Task<HttpResponseMessage> SendRequest(HttpClient httpClient, HttpMethod method, string query)
    {
        HttpRequestMessage request = new HttpRequestMessage(method, query);
        return await httpClient.SendAsync(request);
    }

【问题讨论】：

尝试从CreateClient中删除using并将using移动到Execute
此外，您可能don't need to use using with (i.e., dispose) HttpClient。特别是如果您将多次使用它，请将其声明为类级变量，将其初始化一次（在您的 CreateClient 方法中没有using），然后就可以了.

标签： c# .net rest httpclient

【解决方案1】：

只要 HttpClient 离开 CreateClient 方法中的 using 语句，它就会被释放。去掉 CreateClient 方法中的 using 语句，改为在 Execute 方法中实现 using

public async void Execute()
{
string query = $"<RequestData>" +
$"<firstField>{model.firstField}</firstField>" +
$"<secondField>{model.secondField}</secondField>" +
$"<thirdField>{model.thirdField}</thirdField>" +
    $"</RequestData>";
   using(HttpClient client = CreateClient())
   {
    HttpResponseMessage response = await SendRequest(client, HttpMethod.Put, query);
   }
}

private HttpClient CreateClient()
{
var client = new HttpClient();
   client.BaseAddress = baseAdress;
client.DefaultRequestHeaders.Accept.Clear();
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
return client;
}

private async Task<HttpResponseMessage> SendRequest(HttpClient httpClient, HttpMethod method, string query)
{
HttpRequestMessage request = new HttpRequestMessage(method, query);
return await httpClient.SendAsync(request);
}

【讨论】：

查询是否应该包含整个 url？还是开始在“BaseAddress”中，而查询是 url 的其余部分？
@Jarmoosh 如果您在 HttpClient 上设置 BaseAddress，那么您只需要在基地址之上提供路由，例如 'api/user'