c# .net core 下的网络请求

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本文章是在VS2017的环境下，.net core 1.1版本以上。

在这期间，由于.net core 并不基于IIS，我们的过去的网络请求代码在.net core框架下，有可能会出现不兼容，报错的现象。这里大致介绍下在.net core 下如何进行http请求，主要仍然是GET和POST方法，有错误的地方，欢迎指正！

先来说POST,POST我实现了三种方法，前两种基于的原理是完全一致的，后面的有些小小的差异，但他们的本质都是http请求，本质上是无区别的，只是实现方法有所不同。

废话不多说，上代码：

POST异步方法：

/// <summary>
/// 异步请求post（键值对形式,可等待的）
/// </summary>
/// <param name="uri">网络基址("http://localhost:59315")</param>
/// <param name="url">网络的地址("/api/UMeng")</param>
/// <param name="formData">键值对List<KeyValuePair<string, string>> formData = new List<KeyValuePair<string, string>>();formData.Add(new KeyValuePair<string, string>("userid", "29122"));formData.Add(new KeyValuePair<string, string>("umengids", "29122"));</param>
/// <param name="charset">编码格式</param>
/// <param name="mediaType">头媒体类型</param>
/// <returns></returns>
public async Task<string> HttpPostAsync(string uri, string url, List<KeyValuePair<string, string>> formData = null, string charset = "UTF-8", string mediaType = "application/x-www-form-urlencoded")
{ string tokenUri = url;
var client = new HttpClient();
client.BaseAddress = new Uri(uri);
HttpContent content = new FormUrlEncodedContent(formData);
content.Headers.ContentType = new MediaTypeHeaderValue(mediaType);
content.Headers.ContentType.CharSet = charset;
for (int i = ; i < formData.Count; i++)
{
content.Headers.Add(formData[i].Key, formData[i].Value);
} HttpResponseMessage resp = await client.PostAsync(tokenUri, content);
resp.EnsureSuccessStatusCode();
string token = await resp.Content.ReadAsStringAsync();
return token;
}

POST同步方法：

/// <summary>
/// 同步请求post（键值对形式）
/// </summary>
/// <param name="uri">网络基址("http://localhost:59315")</param>
/// <param name="url">网络的地址("/api/UMeng")</param>
/// <param name="formData">键值对List<KeyValuePair<string, string>> formData = new List<KeyValuePair<string, string>>();formData.Add(new KeyValuePair<string, string>("userid", "29122"));formData.Add(new KeyValuePair<string, string>("umengids", "29122"));</param>
/// <param name="charset">编码格式</param>
/// <param name="mediaType">头媒体类型</param>
/// <returns></returns>
public string HttpPost(string uri, string url, List<KeyValuePair<string, string>> formData = null, string charset = "UTF-8", string mediaType = "application/x-www-form-urlencoded")
{
string tokenUri = url;
var client = new HttpClient();
client.BaseAddress = new Uri(uri);
HttpContent content = new FormUrlEncodedContent(formData);
content.Headers.ContentType = new MediaTypeHeaderValue(mediaType);
content.Headers.ContentType.CharSet = charset;
for (int i = ; i < formData.Count; i++)
{
content.Headers.Add(formData[i].Key, formData[i].Value);
} var res = client.PostAsync(tokenUri, content);
res.Wait();
HttpResponseMessage resp = res.Result; var res2 = resp.Content.ReadAsStringAsync();
res2.Wait(); string token = res2.Result;
return token;
}

遗憾的是，同步方法也是基于异步实现的，个人认为这样做会加大系统开销。如果各位有其他的高效实现，请不吝赐教！

接下来是通过流的方式进行POST：

public string Post(string url, string data, Encoding encoding, int type)
{
try
{
HttpWebRequest req = WebRequest.CreateHttp(new Uri(url));
if (type == )
{
req.ContentType = "application/json;charset=utf-8";
}
else if (type == )
{
req.ContentType = "application/xml;charset=utf-8";
}
else
{
req.ContentType = "application/x-www-form-urlencoded;charset=utf-8";
} req.Method = "POST";
//req.Accept = "text/xml,text/javascript";
req.ContinueTimeout = ; byte[] postData = encoding.GetBytes(data);
Stream reqStream = req.GetRequestStreamAsync().Result;
reqStream.Write(postData, , postData.Length);
reqStream.Dispose(); var rsp = (HttpWebResponse)req.GetResponseAsync().Result;
var result = GetResponseAsString(rsp, encoding);
return result; }
catch (Exception ex)
{
throw;
}
}

private string GetResponseAsString(HttpWebResponse rsp, Encoding encoding)
{
Stream stream = null;
StreamReader reader = null; try
{
// 以字符流的方式读取HTTP响应
stream = rsp.GetResponseStream();
reader = new StreamReader(stream, encoding);
return reader.ReadToEnd();
}
finally
{
// 释放资源
if (reader != null) reader.Dispose();
if (stream != null) stream.Dispose();
if (rsp != null) rsp.Dispose();
}
}

这种方式的POST还是将数据写入到流里面，进行POST,之所以写前两个key-value的形式，是为了符合java或者oc的风格，在c#书写的webapi中，由于接收形式是{=value}而不是{key=value}(由webapi的性质决定)，后续我会说如何在webapi中接收（key-value）的形式，适当避免.net后台人员与android和ios的矛盾，从而达到社会主义民主社会的长治久安。

接下来是get，同样同步异步都是由异步实现的，还请各位看官轻喷。

GET：

/// <summary>
/// 异步请求get(UTF-8)
/// </summary>
/// <param name="url">链接地址</param>
/// <param name="formData">写在header中的内容</param>
/// <returns></returns>
public static async Task<string> HttpGetAsync(string url, List<KeyValuePair<string, string>> formData = null)
{
HttpClient httpClient = new HttpClient();
HttpContent content = new FormUrlEncodedContent(formData);
if (formData != null)
{
content.Headers.ContentType = new MediaTypeHeaderValue("application/x-www-form-urlencoded");
content.Headers.ContentType.CharSet = "UTF-8";
for (int i = ; i < formData.Count; i++)
{
content.Headers.Add(formData[i].Key, formData[i].Value);
}
}
var request = new HttpRequestMessage()
{
RequestUri = new Uri(url),
Method = HttpMethod.Get,
};
for (int i = ; i < formData.Count; i++)
{
request.Headers.Add(formData[i].Key, formData[i].Value);
}
var resp = await httpClient.SendAsync(request);
resp.EnsureSuccessStatusCode();
string token = await resp.Content.ReadAsStringAsync(); return token;
}

/// <summary>
/// 同步get请求
/// </summary>
/// <param name="url">链接地址</param>
/// <param name="formData">写在header中的键值对</param>
/// <returns></returns>
public string HttpGet(string url, List<KeyValuePair<string, string>> formData = null)
{
HttpClient httpClient = new HttpClient();
HttpContent content = new FormUrlEncodedContent(formData);
if (formData != null)
{
content.Headers.ContentType = new MediaTypeHeaderValue("application/x-www-form-urlencoded");
content.Headers.ContentType.CharSet = "UTF-8";
for (int i = ; i < formData.Count; i++)
{
content.Headers.Add(formData[i].Key, formData[i].Value);
}
}
var request = new HttpRequestMessage()
{
RequestUri = new Uri(url),
Method = HttpMethod.Get,
};
for (int i = ; i < formData.Count; i++)
{
request.Headers.Add(formData[i].Key, formData[i].Value);
}
var res = httpClient.SendAsync(request);
res.Wait();
var resp = res.Result;
Task<string> temp = resp.Content.ReadAsStringAsync();
temp.Wait();
return temp.Result;
}