最快的方式是直接nuget安装AspNetCore.Authentication.WeChat包。

想要知道是如何实现的，可以看下面github上面的源码。

源码在这里：https://github.com/china-live/QQConnect

使用方式：

1. 安装nuget的包以后，在startup.cs中添加微信授权认证并配置appId和AppSecret，使用缓存保存State数据（微信State Too Long 报错 由于微信的设置，state最多128字节，但是默认生成的state会超出限制，所以需要加入缓存）

   iservices.AddAuthentication().AddWeChat(options =>{options.AppId = Configuration["WeixinSetting:WeixinAppId"];options.AppSecret = Configuration["WeixinSetting:WeixinAppSecret"];options.UseCachedStateDataFormat = true;});

2. 新建一个Controller，编写action

           /// <summary>/// 微信授权登录/// </summary>/// <param name="returnUrl">用户尝试进入的需要登录的页面</param>/// <returns></returns>
           [AllowAnonymous]public ActionResult WxLogin(string returnUrl){string redirectUrl = Url.Action("BaseCallback",new { ReturnUrl = returnUrl });var properties = signInManager.ConfigureExternalAuthenticationProperties("WeChat", redirectUrl);return new ChallengeResult("WeChat", properties);}/// <summary>/// 回调/// </summary>/// <param name="provider"></param>/// <param name="returnUrl">用户最初尝试进入的页面</param>/// <returns></returns>
           [AllowAnonymous]public async Task<IActionResult> BaseCallback(string provider = null, string returnUrl = "/"){try{ExternalLoginInfo info = await signInManager.GetExternalLoginInfoAsync();if (info == null){return RedirectToAction(nameof(Login));}var result = await signInManager.ExternalLoginSignInAsync(info.LoginProvider, info.ProviderKey, false);if (result.Succeeded){return Redirect(returnUrl);}else{Account user = new Account{OpenId = info.Principal.FindFirst(ClaimTypes.NameIdentifier).Value,UserName =info.Principal.FindFirst(ClaimTypes.NameIdentifier).Value};IdentityResult identResult = await userManager.CreateAsync(user);if (identResult.Succeeded){identResult = await userManager.AddLoginAsync(user, info);if (identResult.Succeeded){await signInManager.SignInAsync(user, false);return Redirect(returnUrl);}}return AccessDenied();}}catch (Exception ex){return Content("发生错误：" + ex);}}