Question

我正在使用EF Code First来查询和创建数据库。我的一个实体（关系）具有两个到同一实体（活动）的导航属性。我的问题是，如果我使用EF来创建数据库模式，它将创建四个外键列和约束而不是两个。

以下是相关的代码部分：

活动类：

Chrome 47.0.2526 (Windows 10 0.0.0) DebugDirective should compile in component template FAILED
    Failed: The selector "#root0" did not match any elements
    Error: The selector "#root0" did not match any elements
        at new BaseException (C:/~/node_modules/angular2/bundles/angular2.dev.js:8080:21)
        at DomRenderer_.createRootHostView (C:/~/node_modules/angular2/bundles/angular2.dev.js:15248:15)
        at AppViewManager_.createRootHostView (C:/~/node_modules/angular2/bundles/angular2.dev.js:11265:52)
        at C:/~/node_modules/angular2/bundles/angular2.dev.js:14531:46
        at Zone.run (C:/~/node_modules/angular2/bundles/angular2-polyfills.js:138:17)
        at Zone.run (C:/~/node_modules/angular2/bundles/testing.dev.js:2544:30)
        at zoneBoundFn (C:/~/node_modules/angular2/bundles/angular2-polyfills.js:111:19)
        at lib$es6$promise$$internal$$tryCatch (C:/~/node_modules/angular2/bundles/angular2-polyfills.js:1511:16)
        at lib$es6$promise$$internal$$invokeCallback (C:/~/node_modules/angular2/bundles/angular2-polyfills.js:1523:17)
        at lib$es6$promise$$internal$$publish (C:/~/node_modules/angular2/bundles/angular2-polyfills.js:1494:11)
        at C:/~/node_modules/angular2/bundles/angular2-polyfills.js:243:5
        at microtask (C:/~/node_modules/angular2/bundles/testing.dev.js:2557:15)
        at Zone.run (C:/~/node_modules/angular2/bundles/angular2-polyfills.js:138:17)
        at Zone.run (C:/~/node_modules/angular2/bundles/testing.dev.js:2544:30)
        at zoneBoundFn (C:/~/node_modules/angular2/bundles/angular2-polyfills.js:111:19)
        at lib$es6$promise$asap$$flush (C:/~/node_modules/angular2/bundles/angular2-polyfills.js:1305:9)
    Failed: Cannot read property 'hostView' of undefined
    TypeError: Cannot read property 'hostView' of undefined
        at new ComponentFixture_ (C:/~/node_modules/angular2/bundles/testing.dev.js:2047:97)
        at C:/~/node_modules/angular2/bundles/testing.dev.js:2145:16
        at Zone.run (C:/~/node_modules/angular2/bundles/angular2-polyfills.js:138:17)
        at Zone.run (C:/~/node_modules/angular2/bundles/testing.dev.js:2544:30)
        at zoneBoundFn (C:/~/node_modules/angular2/bundles/angular2-polyfills.js:111:19)
        at lib$es6$promise$$internal$$tryCatch (C:/~/node_modules/angular2/bundles/angular2-polyfills.js:1511:16)
        at lib$es6$promise$$internal$$invokeCallback (C:/~/node_modules/angular2/bundles/angular2-polyfills.js:1523:17)
        at lib$es6$promise$$internal$$publish (C:/~/node_modules/angular2/bundles/angular2-polyfills.js:1494:11)
        at C:/~/node_modules/angular2/bundles/angular2-polyfills.js:243:5
        at microtask (C:/~/node_modules/angular2/bundles/testing.dev.js:2557:15)
        at Zone.run (C:/~/node_modules/angular2/bundles/angular2-polyfills.js:138:17)
        at Zone.run (C:/~/node_modules/angular2/bundles/testing.dev.js:2544:30)
        at zoneBoundFn (C:/~/node_modules/angular2/bundles/angular2-polyfills.js:111:19)
        at lib$es6$promise$asap$$flush (C:/~/node_modules/angular2/bundles/angular2-polyfills.js:1305:9)
    Failed: Cannot read property 'detectChanges' of undefined
    TypeError: Cannot read property 'detectChanges' of undefined
        at C:/~/dist/scripts/core/components/people/people.component.spec.js:17:32
        at C:/~/dist/scripts/core/components/people/people.component.spec.js:17:32
        at Zone.run (C:/~/node_modules/angular2/bundles/angular2-polyfills.js:138:17)
        at Zone.run (C:/~/node_modules/angular2/bundles/testing.dev.js:2544:30)
        at zoneBoundFn (C:/~/node_modules/angular2/bundles/angular2-polyfills.js:111:19)
        at lib$es6$promise$$internal$$tryCatch (C:/~/node_modules/angular2/bundles/angular2-polyfills.js:1511:16)
        at lib$es6$promise$$internal$$invokeCallback (C:/~/node_modules/angular2/bundles/angular2-polyfills.js:1523:17)
        at lib$es6$promise$$internal$$publish (C:/~/node_modules/angular2/bundles/angular2-polyfills.js:1494:11)
        at C:/~/node_modules/angular2/bundles/angular2-polyfills.js:243:5
        at microtask (C:/~/node_modules/angular2/bundles/testing.dev.js:2557:15)
        at Zone.run (C:/~/node_modules/angular2/bundles/angular2-polyfills.js:138:17)
        at Zone.run (C:/~/node_modules/angular2/bundles/testing.dev.js:2544:30)
        at zoneBoundFn (C:/~/node_modules/angular2/bundles/angular2-polyfills.js:111:19)
        at lib$es6$promise$asap$$flush (C:/~/node_modules/angular2/bundles/angular2-polyfills.js:1305:9)
Chrome 47.0.2526 (Windows 10 0.0.0): Executed 16 of 16 (1 FAILED) (0.396 secs / 0.167 secs)

关系类：

public class Activity {
    public virtual ICollection<Relationship> Successors { get; set; }
    public virtual ICollection<Relationship> Predecessors { get; set; }
}

关系映射类：

public class Relationship {
    public virtual Activity Activity1 { get; set; }
    public int Activity1_ID { get; set; }
    public virtual Activity Activity2 { get; set; }
    public int Activity2_ID { get; set; }
}

数据库结构：

有没有办法阻止创建最后两列？

Answer 1

这应该只创建2个外键列。

public class Activity
{
    public int Id { set; get; }
    public virtual ICollection<Relationship> Successors { get; set; }
    public virtual ICollection<Relationship> Predecessors { get; set; }
}
public class Relationship
{
    public int Id { set; get; }
    public virtual Activity Activity1 { get; set; }
    public int Activity1_ID { get; set; }
    public virtual Activity Activity2 { get; set; }
    public int Activity2_ID { get; set; }
}

我在OnModelCreating指定关系/ FK性质的DbContext类。

public class MyDb: DbContext
{
    public MyDb():base("EfDbContext")
    {           
    }
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {            
        modelBuilder.Entity<Relationship>()
            .HasRequired(f => f.Activity1)
            .WithMany(f => f.Predecessors)
            .HasForeignKey(g => g.Activity1_ID)
            .WillCascadeOnDelete(false);

        modelBuilder.Entity<Relationship>().
             HasRequired(f => f.Activity2)
            .WithMany(f => f.Successors)
            .HasForeignKey(g => g.Activity2_ID)
            .WillCascadeOnDelete(false);
    }
}

EF Code First，两个导航属性到同一个对象

1 个答案: