当我尝试使用实体框架核心测试更新操作时出现以下错误：

System.InvalidOperationException：无法跟踪实体类型“公司”的实例，因为另一个具有键值“{Id: 1}”的实例已被跟踪。附加现有实体时，请确保仅附加一个具有给定键值的实体实例。

在做了一些研究之后，我尝试了所有我发现的东西：

• 在范围内创建数据库上下文
• 分离并附加我想从数据库上下文更新的对象
• 使用 "AsnoTracking()" 返回要更新的对象，我的存储库实际上是这样做的。

对于测试，我使用 EF 内存数据库和它的夹具，我使用 XUnit 和 .NET 5。 请问我可以得到任何帮助吗？

这是我的代码：

    // The repository I am trying to test
    public class RepositoryBase<T> : ICrudRepository<T> where T : class,IModel
    {
        protected PrjDbContext DatabaseContext { get; set; }

        public RepositoryBase(PrjDbContext databaseContext) => DatabaseContext = databaseContext;

        protected IQueryable<T> FindAll() => DatabaseContext.Set<T>().AsnoTracking();

        protected IQueryable<T> FindBy(Expression<Func<T,bool>> expression) => DatabaseContext.Set<T>().Where(expression).AsnoTracking();

        public void Create(T entity) => DatabaseContext.Set<T>().Add(entity);

        public void Update(T entity) => DatabaseContext.Set<T>().Update(entity);

        public void Delete(T entity) => DatabaseContext.Set<T>().Remove(entity);

        public async Task<IEnumerable<T>> ReadAllAsync() => await FindAll().ToListAsync().ConfigureAwait(false);

        public async Task<T> ReadByIdAsync(int id) => await FindBy(entity => entity.Id.Equals(id)).FirstOrDefaultAsync().ConfigureAwait(false);
    }

    //The Database context  
    public partial class PrjDbContext : DbContext
    {
        public PrjDbContext()
        {
            
        }

        public PrjDbContext(DbContextOptions<PrjDbContext> options)
            : base(options)
        {
            
        }

        public virtual DbSet<Companies> Companies { get; set; }
       
    }  

    // This is my fixture with the in-memory Database 
    public sealed class PrjSeedDataFixture : IDisposable
    {
        public PrjDbContext DbContext { get; }

        public PrjSeedDataFixture(string name)
        {
            string databaseName = "PrjDatabase_" + name + "_" + DateTime.Now.ToFileTimeUtc();
            DbContextOptions<PrjDbContext> options = new DbContextOptionsBuilder<PrjDbContext>()
                .UseInmemoryDatabase(databaseName)
                .EnableSensitiveDataLogging()
                .Options;

            DbContext = new PrjDbContext(options);

            // Load Companies
            DbContext.Companies.Add(new Companies { Id = 1,Name = "Customer 1",Status = 0,Created = DateTime.Now,LogoName = "FakeLogo.jpg",LogoPath = "/LogoPath/SecondFolder/",ModifiedBy = "Admin" });
            DbContext.Companies.AsnoTracking();

            DbContext.SaveChanges();
        }

        public void Dispose()
        {
            DbContext.Dispose();
        }
    }

测试方法“Update_WhenCalled_UpdateACompanyObject”对我不起作用。

    // And finally,this is my test class,Create_WhenCalled_CreatesnewCompanyObject pass the test,but Update_WhenCalled_UpdateACompanyObject isn't passing the test.
    public class RepositoryBaseCompanyTests
    {
        private Companies _newCompany;
        private PrjDbContext _databaseContext;
        private RepositoryBase<Companies> _sut;
        
        public RepositoryBaseCompanyTests()
        {
            _newCompany = new Companies {Id = 2};
            _databaseContext = new PrjSeedDataFixture("RepositoryBase").DbContext;
            _sut = new RepositoryBase<Companies>(_databaseContext);
        }

        [Fact]
        public void Create_WhenCalled_CreatesnewCompanyObject()
        {
            //act
            _sut.Create(_newCompany);
            _databaseContext.SaveChanges();

            //Assert
            Assert.Equal(2,_databaseContext.Companies.Where( x => x.Id == 2).FirstOrDefault().Id);
            
        }

        [Fact]
        public async void Update_WhenCalled_UpdateACompanyObject()
        {
            //Arrange
            var company = await _sut.ReadByIdAsync(1);
            company.Name = "Customer 2";
            //_databaseContext.Entry(company).State = EntityState.Detached;
            //_databaseContext.Attach(company);
            //_databaseContext.Entry(company).State = EntityState.Modified;

            //act
            _sut.Update(company);
            await _databaseContext.SaveChangesAsync();

            //Assert
            Assert.Equal("Customer 2",_databaseContext.Companies.Where(x => x.Id == 1).FirstOrDefault().Name);
        }
    }