投放并合并两个相同接口的列表，但不同类型 [英] Cast and merge two lists of same interfaces but different types

问题描述

我有两个实体使用相同的界面。我想将我从实体框架获得的两个结果合并到一个 IKules列表：

  public async任务< 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）凡（_someCourseFilterForAgs）; 
 result.Concat（await courses.ToListAsync（））。Cast< IKurs< ITeacherToCourse< IAdditionalTeacherData> IAdditionalTeacherData>>（）; 
} 
返回结果; 
} 
  

如您所见，我尝试用
.Cast< IKurs< ITeacherToCourse< IAdditionalTeacherData>，IAdditionalTeacherData>>（）（抛出InvalidCastException）

是课程，既实现 IKurs ，T1> ，但它们的T1和T2是不同的（但仍然使用相同的接口）：

  public class XtrCourse：Core_Xtr_Course，IKurs< XtrTeacherToCourse，XtrAdditionalTeacherData> 
 {
 public int Nr {get;组; 
 // property 
 
 public ICollection< XtrTeacherToCourse> TeachersToCourses {get;组; } 
} 
 
 public class AgsCourse：Core_Ags_Course，IKurs< AgsTeacherToCourse，AgsAdditionalTeacherData> 
 {
 public int Nr {get;组; } 
 //属性
 
 public ICollection< AgsTeacherToCourse> TeachersToCourses {get;组; } 
} 
 
 public interface IKurs< TTeacherToCourse，TAdditionalTeacherData> 
其中TTeacherToCourse：ITeacherToCourse< TAdditionalTeacherData> 
其中TAdditionalTeacherData：IAdditionalTeacherData 
 {
 int Nr {get;组; } 
 
 ICollection< TTeacherToCourse> TeachersToCourses {get;组; } 
} 
 
 public interface ITeacherToCourse< T>其中T：IAdditionalTeacherData 
 {
 int Nr {get;组; } 
 T AdditionalTeacherData {get;组; } 
} 
 
 public interface IAdditionalTeacherData 
 {
 //属性
} 
  

class AgsTeacherToCourse 和 XtrTeacherToCourse 都实现 ITeacherToCourse
class AgsTeacherToCourse 和 XtrTeacherToCourse 都实现 ITeacherToCourse

如何将它们合并到一个列表？

，两个课程列表来自不同的上下文。这就是为什么我在 GetCourses（）中启动上下文。

解决方案

p>主要问题之一是

 界面ITeacherToCourse< T>其中T：IAdditionalTeacherData 
 {
 int Nr {get;组; } 
 T AdditionalTeacherData {get;组; } 
} 
 
 class XtrTeacherToCourse：ITeacherToCourse< XtrAdditionalTeacherData> 
 {
 public int Nr {get;组; } 
 public XtrAdditionalTeacherData AdditionalTeacherData {get;组; } 
} 
 
 class AgsTeacherToCourse：ITeacherToCourse< AgsAdditionalTeacherData> 
 {
 public int Nr {get;组; } 
 public AgsAdditionalTeacherData AdditionalTeacherData {get;组; } 
} 
  

界面契约定义您只能设置 的值 AdditionalTeacherData 类型 XtrAdditionalTeacherData for XtrAdditionalTeacherData 和 AgsAdditionalTeacherData for AgsTeacherToCourse 。

我们如何确保当我们能够

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

如果您不想设置 AdditionalTeacherData 属性，则可以声明接口，如

  interface ITeacherToCourse< out T>其中T：IAdditionalTeacherData 
 {
 int Nr {get;组; } 
 T AdditionalTeacherData {get; } 
} 
  

AdditionalTeacherData 现在只读和 T 是一个 out T 。

现在我们可以

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

与集合相同。

总界面声明

 界面IAdditionalTeacherData 
 {
 
} 
 
接口ITeacherToCourse< out T>其中T：IAdditionalTeacherData 
 {
 int Nr {get;组; } 
 T AdditionalTeacherData {get; } 
} 
 
接口IKurs< out TTeacherToCourse，out TAdditionalTeacherData> 
其中TTeacherToCourse：ITeacherToCourse< TAdditionalTeacherData> 
其中TAdditionalTeacherData：IAdditionalTeacherData 
 {
 int Nr {get;组; } 
 IEnumerable< TTeacherToCourse> TeachersToCourses {get; } 
} 
  

和实施类

  class XtrAdditionalTeacherData：IAdditionalTeacherData 
 {
 
} 
 
 class XtrTeacherToCourse：ITeacherToCourse< XtrAdditionalTeacherData> 
 {
 public int Nr {get;组; } 
 public XtrAdditionalTeacherData AdditionalTeacherData {get;组; } 
} 
 
 class XtrCourse：IKurs< XtrTeacherToCourse，XtrAdditionalTeacherData> 
 {
 public int Nr {get;组; } 
 public ICollection< XtrTeacherToCourse> TeachersToCourses {get;组; } 
 //显式实现
 IEnumerable< XtrTeacherToCourse> IKurs< XtrTeacherToCourse，XtrAdditionalTeacherData> .TeachersToCourses => TeachersToCourses; 
} 
 
 class AgsAdditionalTeacherData：IAdditionalTeacherData 
 {
 
} 
 
 class AgsTeacherToCourse：ITeacherToCourse< AgsAdditionalTeacherData> 
 {
 public int Nr {get;组; } 
 public AgsAdditionalTeacherData AdditionalTeacherData {get;组; } 
} 
 
 class AgsCourse：IKurs< AgsTeacherToCourse，AgsAdditionalTeacherData> 
 {
 public int Nr {get;组; } 
 public ICollection< AgsTeacherToCourse> TeachersToCourses {get;组; } 
 //显式执行
 IEnumerable< AgsTeacherToCourse> IKurs< AgsTeacherToCourse，AgsAdditionalTeacherData> .TeachersToCourses => TeachersToCourses; 
} 
  

现在我们可以添加没有任何演员的实例

  var collection = new List< IKurs< ITeacherToCourse< IAdditionalTeacherData> IAdditionalTeacherData>>（）; 
 
 collection.Add（new XtrCourse（））; 
 collection.Add（new AgsCourse（））; 
  

I got two entities with using same interface. I want to merge both results I get from entity framework to one list of IKurs:

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;
}

As you can see, I tried casting them both with .Cast<IKurs<ITeacherToCourse<IAdditionalTeacherData>, IAdditionalTeacherData>>() (that throws an InvalidCastException)

These are my Course classes, both implementing IKurs<T1<T2>, T1> but their T1 and T2 are different (but still they use the same interfaces):

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
}

classes AgsTeacherToCourse and XtrTeacherToCourse both implement ITeacherToCourse classes AgsTeacherToCourse and XtrTeacherToCourse both implement ITeacherToCourse

How can I merge them to one list?

In real, both course-lists come from different contexts. That's why I'm initiating the context in GetCourses() twice.

解决方案

One of the main problems is

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; }
}

The interface contract defines that you can only set a value to AdditionalTeacherData of type XtrAdditionalTeacherData for XtrAdditionalTeacherData and AgsAdditionalTeacherData for AgsTeacherToCourse.

How can we ensure this contract when we were able to

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

If you do not want to set the AdditionalTeacherData property then you can declare the interface like

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

AdditionalTeacherData is now readonly and T is an out T.

Now we are able to

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

With the collections it is the same.

The total interface declaration

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; }
}

and the implementing classes

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;
}

and now we can add the instances without any cast

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

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

这篇关于投放并合并两个相同接口的列表，但不同类型的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！