无法创建“applicationdbcontext”类型的对象。对于设计时支持的不同模式错误答案

【问题标题】：unable to create an object of type 'applicationdbcontext'. For the different patterns supported at design time error无法创建“applicationdbcontext”类型的对象。对于设计时支持的不同模式错误
【发布时间】：2021-08-26 16:09:27
【问题描述】：

当我尝试添加迁移时，此错误不断弹出：

无法为设计时支持的不同模式创建“applicationdbcontext”类型的对象

Startup.cs 代码：

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();
    }

    // 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();
        }
        else
        {
            app.UseExceptionHandler("/Home/Error");
            // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
            app.UseHsts();
        }
        app.UseHttpsRedirection();
        app.UseStaticFiles();

        app.UseRouting();

        app.UseAuthorization();

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

ApplicationDBContext.cs 代码：

public class ApplicationDBContext : DbContext
{
    public ApplicationDBContext(DbContextOptions<ApplicationDBContext> options)
        : base(options)
    {
    }
    public DbSet<Item> Items { get; set; }
}

【问题讨论】：

标签： c# asp.net-mvc visual-studio asp.net-core

【解决方案1】：

ASP.NET Core 应用程序使用依赖注入进行配置。可以使用 Startup.cs 的 ConfigureServices 方法中的 AddDbContext 将 EF Core 添加到此配置中。例如：

   services.AddDbContext<ApplicationDbContext>(
        options => options.UseSqlServer("name=ConnectionStrings:DefaultConnection"));

您也可以使用带有“new”的简单 DbContext 初始化来初始化它

public class ApplicationDbContext : DbContext
{
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlServer(@"YourConnectionStringGoesHere");
    }
}

【讨论】：