无法在 asp.net core EntityFrameworkCore.core 中创建迁移

Posted 2023-03-29

【中文标题】无法在 asp.net core EntityFrameworkCore.core 中创建迁移

【英文标题】：Can't create a migration in asp.net core EntityFrameworkCore.core

【发布时间】：2021-10-14 20:31:02

【问题描述】：

来自程序集“mysql.Data.EntityFrameworkCore, Version=8.0.22.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d”的“MySql.Data.EntityFrameworkCore.Query.Internal.MySQLSqlTranslatingExpressionVisitorFactory”类型中的方法“Create”没有实现. 它给了我这个错误

namespace DBStuff

    public class MessageDBContext : DbContext
    
        public DbSet<Message> Messages  get; set; 

        public MessageDBContext(DbContextOptions<MessageDBContext> options)
            : base(options)
        

        

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        
            modelBuilder.Entity<Message>().ToTable("Messages");

            modelBuilder.Entity<Message>().HasKey(u => u.ID).HasName("PK_Messages");

            modelBuilder.Entity<Message>().HasIndex(p => p.Name).IsUnique().HasDatabaseName("Idx_Name");

            modelBuilder.Entity<Message>().Property(ug => ug.ID).HasColumnType("int").IsRequired();
            modelBuilder.Entity<Message>().Property(ug => ug.Name).HasColumnType("nvarchar(50)").IsRequired();
            modelBuilder.Entity<Message>().Property(ug => ug.Email).HasColumnType("nvarchar(50)").IsRequired(false);
            modelBuilder.Entity<Message>().Property(ug => ug.TelephoneNumber).HasColumnType("int").IsRequired();
            modelBuilder.Entity<Message>().Property(ug => ug._message).HasColumnType("nvarchar(200)").IsRequired();


        
    

消息类：

namespace DBStuff

    public class Message
    

        [Key]
        public int ID  get; set; 

        [Required]
        [MaxLength(50)]
        public string Name  get; set; 


        [MaxLength(25)]
        public string Email  get; set; 

        [Required]
        [MaxLength(15)]
        public int TelephoneNumber  get; set; 

        [Required]
        [MaxLength(150)]
        public string _message  get; set; 
    

启动.CS

namespace Somafix

    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.AddEntityFrameworkMySQL();
            services.AddDbContext<MessageDBContext>(options => options.UseMySQL(Configuration.GetConnectionString("DefaultConnection")));

        

        // 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?");
            );
        
    

HomeController.cs

namespace Somafix.Controllers

    public class HomeController : Controller
    
        private readonly ILogger<HomeController> _logger;
        private readonly MessageDBContext _context;



        public HomeController(ILogger<HomeController> logger, MessageDBContext context)
        
            _logger = logger;
            _context = context;
        

        public IActionResult Index()
        
            return View();
        

        public IActionResult Catalog()
        
            return View();
        

        public IActionResult AboutUs()
        
            return View();
        



        //[HttpGet]
        //public IList<Message> Get()
        //
        //    return (this._context.Messages.ToList());
        //





        public IActionResult ContactUs()
        
            return View();
        


        [ResponseCache(Duration = 0, Location = ResponseCacheLocation.None, NoStore = true)]
        public IActionResult Error()
        
            return View(new ErrorViewModel  RequestId = Activity.Current?.Id ?? HttpContext.TraceIdentifier );
        
    

【问题讨论】：

也许你应该试试Pomelo.EntityFrameworkCore.MySql。 Oracle 的提供程序可能已过时且不稳定。

您的目标项目“Somafix”与您的迁移程序集“DBStuff”不匹配。更改您的目标项目或更改您的迁移程序集。使用 DbContextOptionsBuilder 更改您的迁移程序集。例如。 options.UseSqlServer(connection, b => b.MigrationsAssembly("Somafix"))。默认情况下，迁移程序集是包含 DbContext 的程序集。通过使用包管理器控制台的默认项目下拉列表，或从包含迁移项目的目录中执行“dotnet ef”，将您的目标项目更改为迁移项目。

现在这个错误啊

我的数据库是空的

已解决 aaa :D 是的

【参考方案1】：

已经解决了！

所以我更改了 Nuget 包。我使用的是 mysql.data.entityframeworkcore，现在我使用的是 pomelo.entityframeworkcore.mysql。 我在启动课上写了这个

services.AddDbContext(options => options.UseMySql(connectionString,ServerVersion.AutoDetect(connectionString), b=> b.MigrationsAssembly("Somafix"))); 其中Somafix是我的asp mvc项目，启动类所在的地方