Question

我在Startup.cs文件上指定我在实体项目中创建的上下文类以及为connectionString创建的connectionString数据。但是为什么我会收到此错误？

错误消息：严重性代码说明项目文件行抑制状态错误CS0311的类型 'Microsoft.ApplicationInsights.Extensibility.Implementation.UserContext' 不能在通用类型中用作类型参数“ TContext”，或方法 'EntityFrameworkServiceCollectionExtensions.AddDbContext（IServiceCollection，操作，ServiceLifetime，ServiceLifetime）”。没有来自的隐式引用转换 'Microsoft.ApplicationInsights.Extensibility.Implementation.UserContext' 至 'Microsoft.EntityFrameworkCore.DbContext'。 EntityFramework2 C：\ Users \ xsamu \ source \ repos \ EntityFramework2 \ EntityFramework2 \ Startup.cs 29有效

启动类：

namespace EntityFramework2
{
    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<UserContext>(options => options.UseSqlServer(Configuration.GetConnectionString("DevConnection")));
        }

        // 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?}");
            });
        }
    }
}

实体配置：

namespace EntityFramework2
{
    public class EntityConfiguration : IEntityTypeConfiguration<User>
    {
        public void Configure(EntityTypeBuilder<User> builder)
        {
            builder.HasOne<Department>(navigationExpression: s => s.Name)
                .WithOne(sa => sa.User)
                .HasForeignKey<Department>(sa => sa.DepartmentId);

            builder.HasOne<Title>(navigationExpression: s => s.TitleCode)
               .WithOne(sa => sa.User)
               .HasForeignKey<Title>(sa => sa.TitleId);

            builder.HasOne<Position>(navigationExpression: s => s.PositionCode)
               .WithOne(sa => sa.User)
               .HasForeignKey<Position>(sa => sa.PositionId);
        }
    }
}

Answer 1

没有从“ Microsoft.ApplicationInsights.Extensibility.Implementation.UserContext”到“ Microsoft.EntityFrameworkCore.DbContext”的隐式引用转换。

该消息告诉您，您的UserContext类不是从DbContext继承的，这是强制性的。

它看起来应该像这样：

public class BloggingContext : DbContext
{
    public BloggingContext(DbContextOptions<BloggingContext> options)
        : base(options)
    { }

    public DbSet<Blog> Blogs { get; set; }
}

有关更多信息，请参见EF Core Tutorial和Configuring a DbContext。

Answer 2

您的UserContext是否继承DbContext类？

Answer 3

只需让您的上下文 UserContext 继承自 DbContext 类，如下面的代码，您就可以开始了：

public class UserContext : DbContext
{
    public UserContext (DbContextOptions<UserContext > options)
        : base(options)
    { }

    public DbSet<User> Users{ get; set; }
}

CS0311 C＃该类型不能用作通用类型或方法中的类型参数'TContext'。 EntityFrameworkCore

3 个答案: