帮助继承问题 [英] Help with inheritance issues

问题描述

这是我的情况.我有一个BusinessObjectBase类.我的业务对象定义为:

Here is my situation. I have a BusinessObjectBase class. I have my business objects defined as:

public class Appointment
    inherits businessObjectBase

然后，我创建了一个定义为
的基本集合类

Then I made a base collection class defined as

Public Class BusinessObjectCollectionBase(of T as {BusinessObjectBase})
   inherits bindinglist(of T)

然后，将特定的集合类定义为

I then define my specific collection classes as

Public Class AppointmentCollection
    inherits businessObjectCollectionBase(of Appointment)

为什么我不能执行以下操作:

why cant i do the following:

Dim Appcoll as AppointmentCollection
    Dim Coll as businessObjectCollectionBase(of BusinessObjectBase) = Appcoll

我可以将对象定义为businessObjectBase并将其设置为约会对象，而不会出现任何问题，但是我认为对于集合而言，本质上是相同的事情是不允许的.我只是完全以错误的方式来解决这个问题，还是有办法解决这个问题?

i can define an object as a businessObjectBase and set it to an Appointment Object without any problems, but what i would think would be essentially the same thing for the collection is not allowed. Am i just totally going about this the wrong way, or is there a way to work around this?

推荐答案

是的，您不能这样做.我知道，很烂.

解决此问题的简单方法是将AddRange方法插入到BusinessObjectCollectionBase中:

Yeah, you can''t do that. I know, it sucks.

The easy way to work around is to throw in a AddRange method to your BusinessObjectCollectionBase:

Public Class BusinessObjectCollectionbase(Of T As BusinessObjectBase)
    Inherits BindingList(Of T)

    Public Sub AddRange(values As IEnumerable(Of T))
        For Each Item As T In values
            Me.Add(Item)
        Next
    End Sub
End Class

然后在您的代码中:

and then in your code:

Dim appointments As New AppointmentCollection
Dim businessBases As New BusinessObjectCollectionbase(Of BusinessObjectBase)
 
businessBases.AddRange(appointments)

中提琴！现在，两个集合都拥有对相同对象的引用，但它们具有不同的类型.

Viola! Both collections now hold references to the same objects but as differing types.

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