Question

我在一个项目中，实体使用额外的类来映射它们之间的关系，例如：

public class MainEnt 
{
    public int Id { get; set; }
    public string Description { get; set; }

    public ICollection<MainEntAnotherEnt> AnotherEnts{get;set;}
}

public class AnotherEnt 
{
    public int Id { get; set; }
    public string Description { get; set; }
}

public class MainEntAnotherEnt
{
    public int Id { get; set; }
    public int MainEntId{ get; set; }
    public int AnotherEntId{ get; set; }
}

该项目还使用自动迁移，因此在其中一次迁移中显式创建了MainEntAnotherEnt表。

        CreateTable(
               "dbo.MainEntAnotherEnt",
               c => new
               {
                   Id = c.Int(nullable: false, identity: true),
                   MainEntId = c.Int(nullable: false),
                   AnotherEntId = c.Int(nullable: false),
               })
               .PrimaryKey(t => new { t.Id })
               .ForeignKey("dbo.AnotherEnt", t => t.AnotherEntId)
               .ForeignKey("dbo.MainEnt", t => t.MainEntId)
               .Index(t => t.MainEntId)
               .Index(t => t.AnotherEntId);

我想改变这种方法，因此我们摆脱了MainEntAnotherEnt类，我们可以使用映射来完成它，所以我做了这些更改：

public class MainEnt 
{
    public int Id { get; set; }
    public string Description { get; set; }

    public virtual ICollection<AnotherEnt> AnotherEnts{get;set;}
}

public class AnotherEnt 
{
    public int Id { get; set; }
    public string Description { get; set; }

    public virtual ICollection<MainEnt> MainEnt {get;set;}
}


   modelBuilder.Entity<MainEnt >()
            .HasMany(m => m.AnotherEnts)
            .WithMany(a => a.MainEnt)
            .Map(ma =>
            {
                ma.MapLeftKey("MainEntId");
                ma.MapRightKey("AnotherEntId");
                ma.ToTable("MainEntAnotherEnt");
            });

但是我收到了错误：

[InvalidOperationException：Sequence不包含匹配元素]      System.Linq.Enumerable.Single（IEnumerable`1 source，Func`2谓词）+472
     System.Data.Entity.Migrations.Infrastructure.d__70.MoveNext（）+ 471
     System.Linq.d__22`3.MoveNext（）+355
     System.Linq.d__63`1.MoveNext（）+79
     System.Collections.Generic.List`1..ctor（IEnumerable`1 collection）+504
     System.Linq.Enumerable.ToList（IEnumerable`1 source）+70

     System.Data.Entity.Migrations.Infrastructure.EdmModelDiffer.FindAssociationTypePairs（ICollection`1 entityTypePairs）+862
     System.Data.Entity.Migrations.Infrastructure.EdmModelDiffer.Diff（ModelMetadata source，ModelMetadata target，Lazy`1 modificationCommandTreeGenerator，MigrationSqlGenerator migrationSqlGenerator，String sourceModelVersion，String targetModelVersion）+222
     System.Data.Entity.Migrations.Infrastructure.EdmModelDiffer.Diff（XDocument sourceModel，XDocument targetModel，Lazy`1 modificationCommandTreeGenerator，MigrationSqlGenerator migrationSqlGenerator，String sourceModelVersion，String targetModelVersion）+588
     System.Data.Entity.Migrations.DbMigrator.IsModelOutOfDate（XDocument model，DbMigration lastMigration）+72
     System.Data.Entity.Migrations.DbMigrator.Upgrade（IEnumerable`1 pendingMigrations，String targetMigrationId，String lastMigrationId）+342
     System.Data.Entity.Migrations.DbMigrator.UpdateInternal（String targetMigration）+609
     System.Data.Entity.Migrations.DbMigrator.EnsureDatabaseExists（Action mustSucceedToKeepDatabase）+609
     System.Data.Entity.Migrations.DbMigrator.Update（String targetMigration）+116
     System.Data.Entity.MigrateDatabaseToLatestVersion`2.InitializeDatabase（TContext context）+156
     System.Data.Entity.Internal.InternalContext.PerformInitializationAction（Action action）+71
     System.Data.Entity.Internal.InternalContext.PerformDatabaseInitialization（）+ 482
     System.Data.Entity.Internal.RetryAction`1.PerformAction（TInput input）+174
     System.Data.Entity.Internal.LazyInternalContext.InitializeDatabaseAction（Action`1 action）+273
     System.Data.Entity.Database.Initialize（布尔力）+80

任何有关如何解决此问题的指导都将非常感谢！

切换到HasMany（）并获取Sequence不包含匹配元素错误

0 个答案: