EF Core 2.0 - 在添加时出现 System.NotSupportedException

Question

我正在使用EF Core 2.0。 我有一个包含4列的表，其中PK由所有4列组成。其中一列（IsDefault）是数据库中的位字段。 如果我插入一个将IsDefault设置为true的记录，则一切正常。如果我插入一个将IsDefault设置为false的记录，我会得到以下异常：

System.NotSupportedException occurred
  HResult=0x80131515
  Message=The 'IsDefault' on entity type 'ChromeMileageRestrictionTest' does not have a value set and no value generator is available for properties of type 'bool'. Either set a value for the property before adding the entity or configure a value generator for properties of type 'bool'.
  Source=<Cannot evaluate the exception source>
  StackTrace:
   at Microsoft.EntityFrameworkCore.ValueGeneration.ValueGeneratorSelector.Create(IProperty property, IEntityType entityType)
   at Microsoft.EntityFrameworkCore.ValueGeneration.RelationalValueGeneratorSelector.Create(IProperty property, IEntityType entityType)
   at Microsoft.EntityFrameworkCore.ValueGeneration.Internal.SqlServerValueGeneratorSelector.Create(IProperty property, IEntityType entityType)
   at Microsoft.EntityFrameworkCore.ValueGeneration.ValueGeneratorSelector.<>c__DisplayClass6_0.<Select>b__0(IProperty p, IEntityType e)
   at Microsoft.EntityFrameworkCore.ValueGeneration.ValueGeneratorCache.<>c.<GetOrAdd>b__3_0(CacheKey ck)
   at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey key, Func`2 valueFactory)
   at Microsoft.EntityFrameworkCore.ValueGeneration.ValueGeneratorCache.GetOrAdd(IProperty property, IEntityType entityType, Func`3 factory)
   at Microsoft.EntityFrameworkCore.ValueGeneration.ValueGeneratorSelector.Select(IProperty property, IEntityType entityType)
   at Microsoft.EntityFrameworkCore.ValueGeneration.Internal.SqlServerValueGeneratorSelector.Select(IProperty property, IEntityType entityType)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.ValueGenerationManager.Generate(InternalEntityEntry entry)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntityEntry.SetEntityState(EntityState entityState, Boolean acceptChanges, Boolean forceStateWhenUnknownKey)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.EntityGraphAttacher.PaintAction(EntityEntryGraphNode node)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.EntityEntryGraphIterator.TraverseGraph(EntityEntryGraphNode node, Func`2 handleNode)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.EntityGraphAttacher.AttachGraph(InternalEntityEntry rootEntry, EntityState entityState, Boolean forceStateWhenUnknownKey)
   at Microsoft.EntityFrameworkCore.DbContext.SetEntityState(InternalEntityEntry entry, EntityState entityState)
   at Microsoft.EntityFrameworkCore.DbContext.SetEntityState[TEntity](TEntity entity, EntityState entityState)
   at Microsoft.EntityFrameworkCore.DbContext.Add[TEntity](TEntity entity)
   at DAL.Tests.UnitTest1.TestMethod1() in C:\Users\jkruer\Source\Repos\JLM.App.ChromeIncentivesService\DAL.Tests\UnitTest1.cs:line 12

我创建了一个非常简化的版本，并能够使用单个表、单个实体、单个记录、单元测试实现来重现问题。

我的数据库表：

CREATE TABLE [dbo].[ChromeMileageRestrictionTEST](
    [TermID] [varchar](50) NOT NULL,
    [Mileage] [varchar](50) NOT NULL,
    [Residual] [decimal](18, 8) NOT NULL,
    [isDefault] [bit] NOT NULL,
 CONSTRAINT [PK_ChromeMileageRestrictionTEST] PRIMARY KEY CLUSTERED 
(
    [TermID] ASC,
    [Mileage] ASC,
    [Residual] ASC,
    [isDefault] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

GO

ALTER TABLE [dbo].[ChromeMileageRestrictionTEST] ADD  CONSTRAINT [DF_ChromeMileageRestrictionTEST_Residual]  DEFAULT ((0)) FOR [Residual]
GO

ALTER TABLE [dbo].[ChromeMileageRestrictionTEST] ADD  CONSTRAINT [DF_ChromeMileageRestrictionTEST_isDefault]  DEFAULT ((0)) FOR [isDefault]
GO

我的dbContext：

public partial class ReportingContext : DbContext
    {
        public ReportingContext()
        {
        }

        public virtual DbSet<ChromeMileageRestrictionTest> ChromeMileageRestriction { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseSqlServer(@"MyConnectionStringGoesHere");            
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<ChromeMileageRestrictionTest>(entity =>
            {
                entity.HasKey(e => new { e.TermId, e.Mileage, e.Residual, e.IsDefault })                
                .HasName("PK_ChromeMileageRestrictionTest");

                entity.Property(e => e.TermId)
                    .HasColumnName("TermID")
                    .HasMaxLength(50)
                    .IsUnicode(false);

                entity.Property(e => e.Mileage)
                    .HasMaxLength(50)
                    .IsUnicode(false);

                entity.Property(e => e.Residual)
                    .HasColumnType("decimal(18, 8)")
                    .HasDefaultValueSql("((0))");

                entity.Property(e => e.IsDefault)
                    .HasColumnName("isDefault")
                    .HasDefaultValueSql("((0))");
            });
        }
    }

我的实体:

public partial class ChromeMileageRestrictionTest
    {
        public string TermId { get; set; }
        public string Mileage { get; set; }
        public decimal Residual { get; set; }
        public bool IsDefault { get; set; }
    }

我的单元测试：

[TestClass]
    public class UnitTest1
    {
        [TestMethod]
        public void TestMethod1()
        {
            var dbContext = new ReportingContext();
            dbContext.Add(new ChromeMileageRestrictionTest 
            {
                TermId = "6078915-0-0",
                Mileage = "15,000",
                Residual = 45.00000000M,
                IsDefault = true //THIS WORKS
            });
            dbContext.Add(new ChromeMileageRestrictionTest 
            {
                TermId = "6078915-0-0",
                Mileage = "15,000",
                Residual = 45.00000000M,
                IsDefault = false //THIS THROWS AN EXCEPTION
            });
            dbContext.SaveChanges();
        }
    }

我已经苦思冥想了一段时间，但还是无法理解。非常感谢您的帮助！

谢谢！

- jkruer01

---

你是否为了测试而尝试将ChromeMileageRestrictionTest中的类型更改为byte，并在位列中插入1或0？由于你只有一个位字段 - 你也可以尝试在数据库中使用tinyint字段。 - fredrik

您正在添加相同的记录两次，看起来是这样。尝试编辑一些数据，使其不完全相同。如果您的主键在所有这些列上，则它们应该是唯一的。我认为您的错误是一个虚假的阳性，真正的潜在问题是您正在编写的数据不是唯一的，需要唯一。 - Aaron. S

您还要添加两条记录，请先添加一条并保存，然后再添加下一条并保存。这样需要执行两次SaveChanges而不是一次。 - Aaron. S

@fredrik，EntityFramework 的标准约定不是使用布尔属性和位字段吗？我不认为我完全理解你的建议。 - jkruer01

请查看此链接：https://github.com/aspnet/EntityFrameworkCore/issues/7163 这是一个备受争议的问题。我不理解 EF 在这里的取向。或者请查看此链接：https://github.com/aspnet/EntityFrameworkCore/issues/8540。 - Gert Arnold

Answer 1

这是一个重复的问题: Entity Framework在插入查询中不包括具有默认值的列

简短概述: 我从数据库和DbContext映射中都移除了IsDefault字段上的False默认值。这解决了问题。

- jkruer01