操作失敗，因爲名爲'IX_ID'的索引或統計信息已經存在於'TestAs'表上？

Question

我使用EF4.3.1代碼首先，我有如下的代碼，

namespace ConsoleApplication5 
{ 
    class Program 
    { 
     static void Main(string[] args) 
     { 
      using (var context = new myContext()) 
      { 
       TestA ta = new TestA(); 
       ta.Name = "Hero"; 
       TestB tb = new TestB(); 
       tb.Name = "Allen"; 
       TestC tc = new TestC(); 
       tc.Name = "Iverson"; 
       ta.tb = tb; 
       ta.tc = tc; 
       context.testASet.Add(ta); 
      } 
     } 
    } 

    class TestA 
    { 
     public int ID { get; set; } 

     public string Name { get; set; } 

     public TestB tb { get; set; } 

     public TestC tc { get; set; } 
    } 

    class TestB 
    { 
     public int ID { get; set; } 

     public string Name { get; set; } 

     public TestA ta { get; set; } 
    } 

    class TestC 
    { 
     public int ID { get; set; } 

     public string Name { get; set; } 

     public TestA ta { get; set; } 
    } 

    class myContext : DbContext 
    { 
     public DbSet<TestA> testASet { get; set; } 
     public DbSet<TestB> testBSet { get; set; } 
     public DbSet<TestC> testCSet { get; set; } 

     protected override void OnModelCreating(DbModelBuilder modelBuilder) 
     { 
      modelBuilder.Entity<TestB>().HasOptional(x => x.ta).WithRequired(); 
      modelBuilder.Entity<TestC>().HasOptional(x => x.ta).WithRequired(); 

      modelBuilder.Entity<TestA>().Property(x => x.ID).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity); 
      modelBuilder.Entity<TestB>().Property(x => x.ID).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity); 
      modelBuilder.Entity<TestC>().Property(x => x.ID).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity); 


     } 
    } 
} 

當我調試項目，拋出異常，「操作失敗，因爲索引或名稱爲「統計IX_ID '已經存在於'TestAs'表上。「 但是，如果我從代碼中，只有「種皮」和「TESTB」刪除「TESTC」，修改爲下面的代碼，

namespace ConsoleApplication5 
{ 
    class Program 
    { 
     static void Main(string[] args) 
     { 
      using (var context = new myContext()) 
      { 
       TestA ta = new TestA(); 
       ta.Name = "Hero"; 
       TestB tb = new TestB(); 
       tb.Name = "Allen";    
       ta.tb = tb; 
       context.testASet.Add(ta); 
      } 
     } 
    } 

    class TestA 
    { 
     public int ID { get; set; } 

     public string Name { get; set; } 

     public TestB tb { get; set; } 

    } 

    class TestB 
    { 
     public int ID { get; set; } 

     public string Name { get; set; } 

     public TestA ta { get; set; } 
    } 


    class myContext : DbContext 
    { 
     public DbSet<TestA> testASet { get; set; } 
     public DbSet<TestB> testBSet { get; set; } 

     protected override void OnModelCreating(DbModelBuilder modelBuilder) 
     { 
      modelBuilder.Entity<TestB>().HasOptional(x => x.ta).WithRequired(); 

      modelBuilder.Entity<TestA>().Property(x => x.ID).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity); 
      modelBuilder.Entity<TestB>().Property(x => x.ID).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity); 

     } 
    } 
} 

一切正常。有人知道爲什麼拋出異常嗎？

Answer 1

您正在使用具有一個從屬實體和2個主要實體的共享主鍵映射。根據您的mapping主鍵TestA是FK到TestB以及TestC。這就是爲什麼EF在嘗試創建2個同名的FK時抱怨。

IMO這不是一個實際的情況。解釋實體之間的關係，以便更真實地模擬情況。