投射和合并两个相同接口但不同类型的列表

Question

我得到了两个使用相同接口的实体。我想从实体框架两个结果我得到合并的IKurs一个列表：

public async Task<IEnumerable<IKurs<ITeacherToCourse<IAdditionalTeacherData>, IAdditionalTeacherData>>> GetCourses(bool takeXtr) 
{ 
    IEnumerable<IKurs<ITeacherToCourse<IAdditionalTeacherData>, IAdditionalTeacherData>> result = new List<IKurs<ITeacherToCourse<IAdditionalTeacherData>, IAdditionalTeacherData>>(); 
    if (takeXtr) 
     using (var context = new Context()) 
     { 
      var courses = context.XtrCourses.Include(x=>x.TeachersToCourses).Where(_someCourseFilterForAgs); 
      result.Concat(await courses.ToListAsync()).Cast<IKurs<ITeacherToCourse<IAdditionalTeacherData>, IAdditionalTeacherData>>(); 
     } 

    using (var context = new Context()) 
    { 
     var courses = context.AgsCourses.Include(x=>x.TeachersToCourses).Where(_someCourseFilterForAgs); 
     result.Concat(await courses.ToListAsync()).Cast<IKurs<ITeacherToCourse<IAdditionalTeacherData>, IAdditionalTeacherData>>(); 
    } 
    return result; 
} 

正如你所看到的，我试着用 .Cast<IKurs<ITeacherToCourse<IAdditionalTeacherData>, IAdditionalTeacherData>>()铸造他们两个（即引发InvalidCastException）

这些都是我的Course类，既实现IKurs<T1<T2>, T1>但它们的T1和T2是不同的（但是仍然它们使用相同的接口）：

public class XtrCourse : Core_Xtr_Course, IKurs<XtrTeacherToCourse, XtrAdditionalTeacherData> 
{ 
    public int Nr { get; set; } 
    // properties 

    public ICollection<XtrTeacherToCourse> TeachersToCourses { get; set; } 
} 

public class AgsCourse : Core_Ags_Course, IKurs<AgsTeacherToCourse, AgsAdditionalTeacherData> 
{ 
    public int Nr { get; set; } 
    // properties 

    public ICollection<AgsTeacherToCourse> TeachersToCourses { get; set; } 
} 

public interface IKurs<TTeacherToCourse, TAdditionalTeacherData> 
     where TTeacherToCourse : ITeacherToCourse<TAdditionalTeacherData> 
     where TAdditionalTeacherData: IAdditionalTeacherData 
{ 
    int Nr { get; set; } 

    ICollection<TTeacherToCourse> TeachersToCourses { get; set; } 
} 

public interface ITeacherToCourse<T> where T : IAdditionalTeacherData 
{ 
    int Nr { get; set; } 
    T AdditionalTeacherData { get; set; } 
} 

public interface IAdditionalTeacherData 
{ 
    // properties 
} 

类AgsTeacherToCourse个XtrTeacherToCourse都实现ITeacherToCourse 类AgsTeacherToCourse和XtrTeacherToCourse都实现ITeacherToCourse

我怎样才能将它们合并到一个列表？

实际上，两个课程列表都来自不同的环境。这就是为什么我在GetCourses()两次启动上下文。

Answer 1

一个主要的问题是

interface ITeacherToCourse<T> where T : IAdditionalTeacherData 
{ 
    int Nr { get; set; } 
    T AdditionalTeacherData { get; set; } 
} 

class XtrTeacherToCourse : ITeacherToCourse<XtrAdditionalTeacherData> 
{ 
    public int Nr { get; set; } 
    public XtrAdditionalTeacherData AdditionalTeacherData { get; set; } 
} 

class AgsTeacherToCourse : ITeacherToCourse<AgsAdditionalTeacherData> 
{ 
    public int Nr { get; set; } 
    public AgsAdditionalTeacherData AdditionalTeacherData { get; set; } 
} 

接口定义的合同，你只能设置一个值XtrAdditionalTeacherData类型的AdditionalTeacherData为XtrAdditionalTeacherData和AgsAdditionalTeacherData为AgsTeacherToCourse。

我们怎样才能保证这个合同的时候，我们能够

ITeacherToCourse<IAdditionalTeacherData> ttc = new XtrTeacherToCourse(); 
ttc.AdditionalTeacherData = new AgsAdditionalTeacherData(); 

如果你不想设置的AdditionalTeacherData属性，那么你可以声明接口一样

interface ITeacherToCourse<out T> where T : IAdditionalTeacherData 
{ 
    int Nr { get; set; } 
    T AdditionalTeacherData { get; } 
} 

AdditionalTeacherData是现在只读和T是out T。

现在我们能够

ITeacherToCourse<IAdditionalTeacherData> ttc; 
ttc = new XtrTeacherToCourse(); 
ttc = new AgsTeacherToCourse(); 

有了它相同的集合。

总接口声明

interface IAdditionalTeacherData 
{ 

} 

interface ITeacherToCourse<out T> where T : IAdditionalTeacherData 
{ 
    int Nr { get; set; } 
    T AdditionalTeacherData { get; } 
} 

interface IKurs<out TTeacherToCourse, out TAdditionalTeacherData> 
    where TTeacherToCourse : ITeacherToCourse<TAdditionalTeacherData> 
    where TAdditionalTeacherData : IAdditionalTeacherData 
{ 
    int Nr { get; set; } 
    IEnumerable<TTeacherToCourse> TeachersToCourses { get; } 
} 

和实现类

class XtrAdditionalTeacherData : IAdditionalTeacherData 
{ 

} 

class XtrTeacherToCourse : ITeacherToCourse<XtrAdditionalTeacherData> 
{ 
    public int Nr { get; set; } 
    public XtrAdditionalTeacherData AdditionalTeacherData { get; set; } 
} 

class XtrCourse : IKurs<XtrTeacherToCourse, XtrAdditionalTeacherData> 
{ 
    public int Nr { get; set; } 
    public ICollection<XtrTeacherToCourse> TeachersToCourses { get; set; } 
    // explicit implementation 
    IEnumerable<XtrTeacherToCourse> IKurs<XtrTeacherToCourse, XtrAdditionalTeacherData>.TeachersToCourses => TeachersToCourses; 
} 

class AgsAdditionalTeacherData : IAdditionalTeacherData 
{ 

} 

class AgsTeacherToCourse : ITeacherToCourse<AgsAdditionalTeacherData> 
{ 
    public int Nr { get; set; } 
    public AgsAdditionalTeacherData AdditionalTeacherData { get; set; } 
} 

class AgsCourse : IKurs<AgsTeacherToCourse, AgsAdditionalTeacherData> 
{ 
    public int Nr { get; set; } 
    public ICollection<AgsTeacherToCourse> TeachersToCourses { get; set; } 
    // explicit implementation 
    IEnumerable<AgsTeacherToCourse> IKurs<AgsTeacherToCourse, AgsAdditionalTeacherData>.TeachersToCourses => TeachersToCourses; 
} 

，现在我们可以在没有任何投

var collection = new List<IKurs<ITeacherToCourse<IAdditionalTeacherData>, IAdditionalTeacherData>>(); 

collection.Add(new XtrCourse()); 
collection.Add(new AgsCourse()); 

Answer 2

无需铸造，您可以添加任何IKurs<ITeacherToCourse<IAdditionalTeacherData>, IAdditionalTeacherData>到您的清单。

interface IMyclass{} 

    class MyType1 : IMyclass {} 

    class MyType2 : IMyclass {} 

    public class SomeClass 
    { 
     private List<IMyclass> MyList = new List<IMyclass>(); 

     public void DoSomething() 
     { 
      MyList.AddRange(new List<IMyclass> { new MyType1(), new MyType1() }); 
      MyList.AddRange(new List<IMyclass> { new MyType2(), new MyType2() }); 
     } 
    }