如何使用c#获取oauth2接口中的认证码和访问码

using System;
using System.Net;
using System.Web;
using System.IO;

string clientId = "YOUR_CLIENT_ID";
string redirectUri = "YOUR_REDIRECT_URI";
string scope = "SCOPE1 SCOPE2"; // 授权范围，根据实际需求填写
string state = "STATE"; // 可选参数，用于防止CSRF攻击

string authorizationUrl = $"https://oauth2.example.com/authorize?client_id={clientId}&redirect_uri={HttpUtility.UrlEncode(redirectUri)}&scope={HttpUtility.UrlEncode(scope)}&state={state}";

Response.Redirect(authorizationUrl);

string code = Request.QueryString["code"]; // 获取认证码
string returnedState = Request.QueryString["state"]; // 获取返回的state参数

// 验证state参数，防止CSRF攻击
if (returnedState != state)
{
    // 处理CSRF攻击
}

if (!string.IsNullOrEmpty(code))
{
    // 获取访问码
    string accessToken = GetAccessToken(code, redirectUri);
    // 使用访问码进行后续操作
    // ...
}

private string GetAccessToken(string code, string redirectUri)
{
    string tokenUrl = "https://oauth2.example.com/token";
    string clientId = "YOUR_CLIENT_ID";
    string clientSecret = "YOUR_CLIENT_SECRET";

    // 构建POST请求参数
    string postData = $"grant_type=authorization_code&code={code}&redirect_uri={HttpUtility.UrlEncode(redirectUri)}&client_id={clientId}&client_secret={clientSecret}";

    // 发送POST请求获取访问码
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(tokenUrl);
    request.Method = "POST";
    request.ContentType = "application/x-www-form-urlencoded";

    using (StreamWriter writer = new StreamWriter(request.GetRequestStream()))
    {
        writer.Write(postData);
    }

    using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
    {
        using (StreamReader reader = new StreamReader(response.GetResponseStream()))
        {
            string responseJson = reader.ReadToEnd();
            // 解析返回的JSON数据，获取访问码
            // ...
            return accessToken;
        }
    }
}