在Startup类的ConfigureServices方法中添加以下代码：

services.AddAutoMapper(typeof(Startup));

并在项目中安装AutoMapper.Extensions.Microsoft.DependencyInjection包，代码示例如下：

using AutoMapper; using Microsoft.AspNetCore.Builder; using Microsoft.AspNetCore.Hosting; using Microsoft.EntityFrameworkCore; using Microsoft.Extensions.Configuration; using Microsoft.Extensions.DependencyInjection; using Microsoft.Extensions.Hosting; using WebApplication1.Data; using WebApplication1.Models;

namespace WebApplication1 { public class Startup { public Startup(IConfiguration configuration) { Configuration = configuration; }

    public IConfiguration Configuration { get; }

    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddControllersWithViews();

        services.AddDbContext(options =>
            options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

        services.AddAutoMapper(typeof(Startup));
    }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
            app.UseMigrationsEndPoint();
        }
        else
        {
            app.UseExceptionHandler("/Home/Error");
            app.UseHsts();
        }

        app.UseHttpsRedirection();
        app.UseStaticFiles();

        app.UseRouting();

        app.UseAuthorization();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapControllerRoute(
                name: "default",
                pattern: "{controller=Home}/{action=Index}/{id?}");
        });
    }
}

}

此时，AutoMapper应该在asp net core 5.0.2中可以正常工作了。