基础
新建项目的，新建登录页的基本操作略，主要说下在实现登录过程碰到的问题，废话不多说，让我们进入主题。
验证码
asp.net.core2.0本身有提供system.drawing命名空间，但是没有Image,Graphics,Bitmap等对象的实现，只能引用第三方的dll来操作。
1、在vs的项目里打开nuget包管理器，搜索关键字“drawing"，显示很多可用的包，选择安装"zkweb.system.drawing" 包
2、实现随机字符串的图片显示代码
public IActionResult ImgCode() ???????{ ???????????int Width = 100; ???????????int Height = 30; ???????????string chkCode = string.Empty; ???????????//颜色列表，用于验证码、噪线、噪点 ???????????Color[] color = { Color.Black, Color.Red, Color.Blue, ???????????????Color.Green, Color.Orange, Color.Brown, Color.DarkBlue }; ???????????//字体列表，用于验证码 ???????????string[] font = { "Times New Roman", "MS Mincho", "Book Antiqua", "Gungsuh", "PMingLiU", "Impact" }; ???????????//验证码的字符集，去掉了一些容易混淆的字符 ???????????char[] character ={ ‘2‘, ‘3‘, ‘4‘, ‘5‘, ‘6‘, ‘8‘, ‘9‘, ???????????????????????????????‘A‘, ‘B‘, ‘C‘, ‘D‘, ‘E‘,‘F‘, ‘G‘, ???????????????????????????????‘H‘, ‘J‘, ‘K‘, ‘L‘, ‘M‘, ‘N‘, ???????????????????????????????‘P‘, ‘R‘, ‘S‘, ‘T‘, ‘W‘, ‘X‘, ‘Y‘ }; ???????????Random rnd = new Random(); ???????????//生成验证码字符串 ???????????for (int i = 0; i < 4; i++) ???????????{ ???????????????chkCode += character[rnd.Next(character.Length)]; ???????????} ???????????//保存验证码的Cookie ???????????//HttpCookie anycookie = new HttpCookie("validateCookie"); ???????????//anycookie.Values.Add("ChkCode", chkCode); ???????????//HttpContext.Current.Response.Cookies["validateCookie"].Values["ChkCode"] = chkCode; ???????????Bitmap bmp = new Bitmap(Width, Height); ???????????Graphics g = Graphics.FromImage(bmp); ???????????g.Clear(Color.White); ???????????//画噪线 ???????????for (int i = 0; i < 2; i++) ???????????{ ???????????????int x1 = rnd.Next(Width); ???????????????int y1 = rnd.Next(Height); ???????????????int x2 = rnd.Next(Width); ???????????????int y2 = rnd.Next(Height); ???????????????Color clr = color[rnd.Next(color.Length)]; ???????????????g.DrawLine(new Pen(clr), x1, y1, x2, y2); ???????????} ???????????//画验证码字符串 ???????????for (int i = 0; i < chkCode.Length; i++) ???????????{ ???????????????string fnt = font[rnd.Next(font.Length)]; ???????????????Font ft = new Font(fnt, 16, FontStyle.Bold); ???????????????Color clr = color[rnd.Next(color.Length)]; ???????????????g.DrawString( ???????????????????chkCode[i].ToString(), ???????????????????ft, ???????????????????new SolidBrush(clr), ???????????????????(float)i * 20 + 20, ???????????????????(float)6 ???????????????????); ???????????} ???????????//画噪点 ???????????for (int i = 0; i < 10; i++) ???????????{ ???????????????int x = rnd.Next(bmp.Width); ???????????????int y = rnd.Next(bmp.Height); ???????????????Color clr = color[rnd.Next(color.Length)]; ???????????????bmp.SetPixel(x, y, clr); ???????????} ???????????//将验证码图片写入内存流，并将其以"image/Png" 格式输出 ???????????MemoryStream ms = new MemoryStream(); ???????????try ???????????{ ???????????????bmp.Save(ms, ImageFormat.Png); ???????????????HttpContext.Session.SetString("chkCode", chkCode); ???????????????Response.Body.Dispose(); ???????????????return File(ms.ToArray(), @"image/png"); ???????????} ???????????finally ???????????{ ???????????????//显式释放资源 ???????????????bmp.Dispose(); ???????????????g.Dispose(); ???????????} ???????}3、运行webapplication正常，验证码没有显示出来，调试发现有Session的错误提示，编译时能正常通过，运行提示“Session has not been configured for this application or request.”，在startup.cs使用session服务
，代码如下：
?public void ConfigureServices(IServiceCollection services) ???????{ ???????????????????????services.AddMvc().AddSessionStateTempDataProvider(); ???????????services.AddSession(); ???????} ???????// This method gets called by the runtime. Use this method to configure the HTTP request pipeline. ???????public void Configure(IApplicationBuilder app, IHostingEnvironment env) ???????{ ???????????if (env.IsDevelopment()) ???????????{ ???????????????app.UseDeveloperExceptionPage(); ???????????????app.UseBrowserLink(); ???????????} ???????????else ???????????{ ???????????????app.UseExceptionHandler("/Home/Error"); ???????????} ???????????app.UseStaticFiles(); ???????????app.UseSession(); ???????????app.UseMvc(routes => ???????????{ ???????????????routes.MapRoute( ???????????????????name: "default", ???????????????????template: "{controller=Home}/{action=Index}/{id?}"); ???????????}); ???????}4、编译，刷新页面，显示验证码效果：
登录动作实现
登录后台，用session保存登录后用户对象信息，session方法里没有发现有能保存值是对象形式，这就有点尴尬了，难道用户的信息用多个key分别去存储，这有点不科学啊，肯定有简单的方式实现。
asp.net core2.0 登录效果实现
原文地址：https://www.cnblogs.com/shuancey/p/8243772.html