EF核心数据为空

Question

关于此状态的大多数答案表明，上下文上的DbSet必须是一个属性。但是，由于该上下文的DbSet是一个属性，因此在这种情况下似乎并非如此。这是我可以用来重现问题的示例代码。请指教。

这里是代码：

DbContext

using Microsoft.EntityFrameworkCore;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace Dal
{
    public class SampleContext : DbContext
    {
        public DbSet<Model.ItemCode> ItemCodes { get; set; }

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

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.ApplyConfiguration(new Mapping.ItemCodeConfiguration());
            base.OnModelCreating(modelBuilder);
        }

        public async Task<IEnumerable<Model.ItemCode>> GetCodesByGroup(int group)
        {
            return await ItemCodes.Where(g => g.GroupId == group).ToListAsync();
        }

    }
}

型号

namespace Dal.Model
{
    public class ItemCode
    {
        public int Id { get; set; }
        public string Code { get; set; }
        public string Description { get; set; }
        public int Quantity { get; set; }
        public int KcId { get; set; }
        public int CategoryId { get; set; }
        public int GroupId { get; set; }
    }
}

数据映射

using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Metadata.Builders;

namespace Dal.Mapping
{
    public class ItemCodeConfiguration : IEntityTypeConfiguration<Model.ItemCode>
    {
        public void Configure(EntityTypeBuilder<Model.ItemCode> builder)
        {
            builder.HasKey(b => b.Id);
            builder.Property(b => b.Description)
                .HasColumnName("Description")
                .HasColumnType("nvarchar(255)")
                .IsRequired();
            builder.Property(b => b.Code)
                .HasColumnName("Code")
                .IsRequired();
            builder.Property(b => b.KcId)
                .HasColumnName("KcId");
            builder.Property(b => b.Quantity)
                .HasColumnName("Quantity");
            builder.Property(b => b.GroupId)
                .HasColumnName("GroupId")
                .IsRequired();
            builder.Property(b => b.CategoryId)
                .HasColumnName("CategoryId")
                .IsRequired();
            builder.ToTable("ItemCode", "lookup");
        }
    }
}

测试类别

using Microsoft.EntityFrameworkCore;
using Xunit;

namespace Dal.Test
{
    public class DataTest
    {
        readonly SampleContext context;
        public DataTest()
        {
            var testContextOptions = new DbContextOptionsBuilder<SampleContext>();
            testContextOptions.UseSqlServer(@"Server=localServerName;Database=SampleAppDb;User Id=SampleUser;Password=sampleUser!Password");
            testContextOptions.UseQueryTrackingBehavior(QueryTrackingBehavior.NoTracking);
            context = new SampleContext(testContextOptions.Options);
        }


        [Fact]
        public async void Test1()
        {
            var codes = await context.GetCodesByGroup(1);
            Assert.NotNull(codes);
            Assert.NotEmpty(codes);
        }
    }
}

Answer 1

找到答案，这是一个愚蠢的错误。错误是存在可空的int列，但属性不可为空。更正的课程：

namespace Dal.Model
{
    public class ItemCode
    {
        public int Id { get; set; }
        public string Code { get; set; }
        public string Description { get; set; }
        public int? Quantity { get; set; }
        public int? KcId { get; set; }
        public int CategoryId { get; set; }
        public int GroupId { get; set; }
    }
}