从 HttpWebRequest 转移到 HttpClient答案

【问题标题】：Moving from HttpWebRequest to HttpClient从 HttpWebRequest 转移到 HttpClient
【发布时间】：2022-12-30 15:44:54
【问题描述】：

我想将一些遗留代码从使用 HttpWebRequest 更新为使用 HttpClient，但我不太确定如何将字符串发送到我正在访问的 REST API。

遗留代码：

HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);
request.Method = "POST";
request.ContentType = "text/xml";
request.ContentLength = payload.Length;
if (credentials != null)
{
     request.Credentials = credentials;
}

// Send the request
Stream requestStream = request.GetRequestStream();
requestStream.Write(payload, 0, payload.Length);
requestStream.Close();

// Get the response
response = (HttpWebResponse)request.GetResponse();

我可以使用 HttpClient.GetStreamAsync 方法并像处理 Web 请求那样使用流吗？或者有没有办法对内容使用 SendAsync 然后得到响应？

【问题讨论】：

有一个关于 HttpClient 的doc。你可能会在那里找到答案

标签： c# .net httpwebrequest dotnet-httpclient

【解决方案1】：

using var handler = new HttpClientHandler { Credentials = ... };
using var client = new HttpClient(handler);

var content = new StringContent(payload, Encoding.UTF8, "text/xml");
var response = await client.PostAsync(uri, content);

我假设 payload 是 string。

【讨论】：

【解决方案2】：

您不需要访问请求流，您可以直接发送有效负载，但如果背后有原因，那么这也是可能的。

//Do not instantiate httpclient like that, use dependency injection instead
var httpClient = new HttpClient();
var httpRequest = new HttpRequestMessage();

//Set the request method (e.g. GET, POST, DELETE ..etc.)
httpRequest.Method = HttpMethod.Post;
//Set the headers of the request
httpRequest.Headers.Add("Content-Type", "text/xml");

//A memory stream which is a temporary buffer that holds the payload of the request
using (var memoryStream = new MemoryStream())
{
    //Write to the memory stream
    memoryStream.Write(payload, 0, payload.Length);

    //A stream content that represent the actual request stream
    using (var stream = new StreamContent(memoryStream))
    {
        httpRequest.Content = stream;

        //Send the request
        var response = await httpClient.SendAsync(httpRequest);


        //Ensure we got success response from the server
        response.EnsureSuccessStatusCode();
        //you can access the response like that
        //response.Content
    }
}

关于凭据，你需要知道这些是什么凭据？是基本授权吗？

如果它是基本身份验证，那么您可以（在 HttpRequestMessage 对象中设置请求 URI 时，您也可以在那里构建凭据。

var requestUri = new UriBuilder(yourEndPoint)
                        {
                            UserName = UsernameInCredentials,
                            Password = PasswordInCredentials,
                        }
                        .Uri;

然后您只需将其设置为请求 URI。阅读更多关于为什么我们不应该像这样实例化HttpClienthere

【讨论】：