SQL Server 无法Map属性,因为它的类型为“object”,而该类型不是受支持的基元类型或有效的实体类型

py49o6xq  于 2023-01-12  发布在  其他
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我在使用Entity Framework处理项目时尝试更改SQL Server数据库。然而,当我更改表并添加1个字符串列Email时,整个系统崩溃,但出现了一个没有任何意义的异常。
我试过增加一些光线的变化,但没有效果。
例外情况:
System.Exception:“无法检索实体:无法Map属性“Users.Email”,因为它的类型为“object”,而该类型不是受支持的基元类型或有效的实体类型。请显式Map此属性,或者使用“[NotMapped]”特性或在“OnModelCreating”中使用“EntityTypeBuilder.Ignore”忽略它。
下面是DbContext

using System.Data.Entity;

namespace PlanetariumModelsFramework
{
    public class PlanetariumServiceContext : DbContext
    {
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            Database.SetInitializer<PlanetariumServiceContext>(null);
            base.OnModelCreating(modelBuilder);
        }

        public DbSet<Performance> Performances { get; set; }
        public DbSet<Poster> Posters { get; set; }
        public DbSet<Ticket> Tickets { get; set; }
        public DbSet<Orders> Orders { get; set; }
        public DbSet<Tier> Tiers { get; set; }
        public DbSet<Hall> Halls { get; set; }
        public DbSet<Users> Users { get; set; }
    }
}

用户模型类:

namespace PlanetariumModelsFramework
{
    public class Users
    {
        public int Id { get; set; }
        public string Username { get; set; } = string.Empty;
        public string Email { get; set; } = string.Empty;
        public string UserPassword { get; set; } = string.Empty;
        public string UserRole { get; set; } = string.Empty;
    }
}

发生错误的存储库类:

namespace PlanetariumRepositories
{
    public class Repository<TEntity> : IRepository<TEntity> where TEntity : class
    {
        protected readonly PlanetariumServiceContext RepositoryPlanetarium;

        public Repository(PlanetariumServiceContext repositoryPatternDemoContext)
        {
            RepositoryPlanetarium = repositoryPatternDemoContext;
        }

        public IQueryable<TEntity> GetAll()
        {
            try
            {
                return RepositoryPlanetarium.Set<TEntity>();
            }
            catch (Exception ex)
            {
                throw new Exception($"Couldn't retrieve entities: {ex.Message}");
            }
        }

        public async Task<TEntity> AddAsync(TEntity entity)
        {
            if (entity == null)
            {
                throw new ArgumentNullException($"{nameof(AddAsync)} entity must not be null");
            }

            try
            {
                await RepositoryPlanetarium.AddAsync(entity);
                await RepositoryPlanetarium.SaveChangesAsync();

                return entity;
            }
            catch (Exception ex)
            {
                throw new Exception($"{nameof(entity)} could not be saved: {ex.Message}");
            }
        }        

        public async Task<TEntity> UpdateAsync(TEntity entity)
        {
            if (entity == null)
            {
                throw new ArgumentNullException($"{nameof(AddAsync)} entity must not be null");
            }

            try
            {
                RepositoryPlanetarium.Update(entity);
                object p = await RepositoryPlanetarium.SaveChangesAsync();

                return entity;
            }
            catch (Exception ex)
            {
                throw new Exception($"{nameof(entity)} could not be updated: {ex.Message}");
            }
        }

        public async Task<TEntity> DeleteAsync(TEntity entity)
        {
            if (entity == null)
            {
                throw new ArgumentNullException($"{nameof(AddAsync)} entity must not be null");
            }

            try
            {
                RepositoryPlanetarium.Remove(entity);
                object p = await RepositoryPlanetarium.SaveChangesAsync();
                return entity;
            }
            catch (Exception ex)
            {
                throw new Exception($"{nameof(entity)} could not be deleted: {ex.Message}");
            }
        }
    }
}

继承它的UsersRepository类(可选):

using PlanetariumModels;

namespace PlanetariumRepositories
{
    public class UsersRepository : Repository<Users>, IUsersRepository
    {
        public UsersRepository(PlanetariumServiceContext repositoryPatternDemoContext) : base(repositoryPatternDemoContext)
        {
        }

        public Task<Users> GetByUsernameAsync(string username)
        {
            return base.GetAll().FirstOrDefaultAsync(x => x.Username == username);
        }

        public Task<Users> GetByEmailAsync(string email)
        {
            return base.GetAll().FirstOrDefaultAsync(x => x.Email == email);
        }

        public new List<Users> GetAll()
        {
            return base.GetAll().ToList<Users>();
        }
    }
}

我的SQL Server表创建脚本:

我试着把类型改为System.String,试着改变它的类型,但是没有任何效果。而且,老实说,我不知道这个错误是没有任何意义的。

eoxn13cs

eoxn13cs1#

谢谢你在评论中的提示。
问题是手动更改数据库,这在使用ORM框架(如EntityFramework)时是禁止的。
简单的迁移就完全解决了这个问题。
为此,我必须在View -〉Package Manager Console中打开软件包管理器。
然后输入以下2个命令进行迁移:
Add-Migration <MigrationName>
还有...
update-database <MigrationName>

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