C# 执行基本的 Web POST 请求

Posted 2021-09-14 制作小程序网站电脑程序

这个方法用的是浏览器最传统的表单提交方式 application/x-www-form-urlencoded，这个方法可用到两种组合数据的方法，一是直接传递数据到 data 对象，二是组合键/值对类型的数据到 parameters 对象，方法内会优先选择 data 对象所带的参数，如果想要以键/值对的方式传递，将 data 对象的值填为空字符串即可，这两个二选一；获取返回值的方法中加入了异常处理，这使得即使在遇到请求服务器发生服务器错误（如 404 等 HTTP 状态）时也可正常获得返回的异常信息，使用时需要注意超时值与字符编码集：

using System;
using System.Net;
using System.Text;
using System.IO;
using System.Collections.Generic;

public string HttpPost(string url, string data = "", IDictionary<string, string> parameters = null, int timeout = 5000, CookieCollection cookies = null)
{
    HttpWebRequest request = null;
    request = WebRequest.Create(url) as HttpWebRequest;
    request.Method = "POST";
    request.ContentType = "application/x-www-form-urlencoded";
    request.Timeout = timeout;
    if (cookies != null)
    {
        request.CookieContainer = new CookieContainer();
        request.CookieContainer.Add(cookies);
    }
    if (!string.IsNullOrWhiteSpace(data))
    {
        byte[] databytes = Encoding.UTF8.GetBytes(data);
        using (Stream stream = request.GetRequestStream())
        {
            stream.Write(databytes, 0, databytes.Length);
        }
    }
    else if (parameters != null && parameters.Count != 0)
    {
        StringBuilder buffer = new StringBuilder();
        int i = 0;
        foreach (string key in parameters.Keys)
        {
            if (i > 0)
            {
                buffer.AppendFormat("&{0}={1}", key, parameters[key]);
            }
            else
            {
                buffer.AppendFormat("{0}={1}", key, parameters[key]);
                i++;
            }
        }
        byte[] kvdata = Encoding.UTF8.GetBytes(buffer.ToString());
        using (Stream stream = request.GetRequestStream())
        {
            stream.Write(kvdata, 0, kvdata.Length);
        }
    }
    try
    {
        using (Stream stream = request.GetResponse().GetResponseStream())
        {
            using (StreamReader reader = new StreamReader(stream, Encoding.UTF8))
            {
                return reader.ReadToEnd();
            }
        }
    }
    catch (WebException ex)
    {
        using (Stream stream = ex.Response.GetResponseStream())
        {
            using (StreamReader reader = new StreamReader(stream, Encoding.UTF8))
            {
                return reader.ReadToEnd();
            }
        }
    }
}

相关环境：
.NET Framework 4.0