vb.net 如何确定类型是否在继承层次结构中
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How to determine if a type is in the inheritance hierarchy
提问by XN16
I need to determine if an object has a specific type in it's inheritance hierarchy, however I can't find a good way of doing it.
我需要确定一个对象在它的继承层次结构中是否具有特定类型，但是我找不到这样做的好方法。
An very basic example version of my classes are:
我的课程的一个非常基本的示例版本是：
Public Class Domain
End Class
Public Class DerivedOne
Inherits Domain
End Class
Public Class DerivedTwo
Inherits DerivedOne
End Class
Public Class DerivedThree
Inherits Domain
End Class
The following does work, however it isn't very elegant in my opinion. Also the more levels of inheritance that get created, the more checks need to be done and it would be easy to forget this piece of code needs to be updated.
以下确实有效，但在我看来它不是很优雅。此外，创建的继承级别越多，需要进行的检查就越多，很容易忘记这段代码需要更新。
If GetType(T) Is GetType(Domain) OrElse _
GetType(T).BaseType Is GetType(Domain) OrElse _
GetType(T).BaseType.BaseType Is GetType(Domain) Then
End If
Is there a way of getting 'Is type of Domain anywhere in T's inheritance hierarchy'?
有没有办法获得“域的类型是否在 T 的继承层次结构中的任何地方”？
(Answers welcome in C# or VB.NET)
（欢迎在 C# 或 VB.NET 中回答）
UPDATE
更新
One bit of vital information I missed out due to my own idiocy!
由于自己的愚蠢，我错过了一点重要的信息！
T is a Type object (from the class' generic type)
T 是一个 Type 对象（来自类的泛型类型）
回答by Dan Puzey
You can use the Type.IsAssignableFrommethod.
您可以使用该Type.IsAssignableFrom方法。
In VB:
在VB中：
If GetType(Domain).IsAssignableFrom(GetType(DerivedThree)) Then
In C#:
在 C# 中：
if (typeof(Domain).IsAssignableFrom(typeof(DerivedThree)))
回答by floydheld
Why is nobody mentioning Type.IsSubclassOf(Type)?
为什么没人提Type.IsSubclassOf(Type)？
https://docs.microsoft.com/en-us/dotnet/api/system.type.issubclassof?view=netframework-4.7.2
https://docs.microsoft.com/en-us/dotnet/api/system.type.issubclassof?view=netframework-4.7.2
Careful, it returns false if called for two equal types ;)
小心，如果调用两个相等的类型，它会返回 false ;)
回答by Kaveh Shahbazian
In C# (VB should have this too) you can use a shorthand to perform checking and using the variable and avoiding the casting part:
在 C# 中（VB 也应该有这个），您可以使用速记来执行检查和使用变量并避免铸造部分：
var val = x as Domain;
And then use vallike this:
然后val像这样使用：
if(val != null)
{
// use val
}
