C# 泛型可以有特定的基类型吗？
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Can C# generics have a specific base type?
提问by Neil C. Obremski
Is it possible for a generic interface's type to be based on a specific parent class?
通用接口的类型是否可能基于特定的父类？
For example:
例如：
public interface IGenericFace<T : BaseClass>
{
}
Obviously the above code doesn't work but if it did, what I'm trying to tell the compiler is that Tmust be a sub-class of BaseClass. Can that be done, are there plans for it, etc.?
显然上面的代码不起作用，但如果它起作用了，我想告诉编译器它T必须是BaseClass. 可以这样做吗，是否有计划等？
I think it would be useful in terms of a specific project, making sure a generic interface/class isn't used with unintended type(s) at compile time. Or also to sort of self-document: show what kind of type is intended.
我认为这在特定项目方面会很有用，确保在编译时不会将通用接口/类与非预期类型一起使用。或者也可以进行自我记录：显示打算使用哪种类型。
采纳答案by Ryan Lundy
public interface IGenericFace<T> where T : SomeBaseClass
回答by Ryan Lundy
yes.
是的。
public interface IGenericFace<T>
where T : BaseClass
{
}
回答by Micah
What your are referring to is called "Generic Constraints". There are numerous constraints that can be put on a generic type.
您所指的称为“通用约束”。可以对泛型类型施加许多约束。
Some basic examples are as follows:
一些基本示例如下：
where T: struct- The type argument must be a value type. Any value type exceptNullable- can be specified. See Using Nullable Types (C# Programming Guide)for more information.where T : class- The type argument must be a reference type; this applies also to any class, interface, delegate, or array type.where T : new()- The type argument must have a public parameterless constructor. When used together with other constraints, thenew()constraint must be specified last.where T : <base class name>- The type argument must be or derive from the specified base class.where T : <interface name>- The type argument must be or implement the specified interface. Multiple interface constraints can be specified. The constraining interface can also be generic.where T : U- The type argument supplied forTmust be or derive from the argument supplied forU. This is called a naked type constraint.
where T: struct- 类型参数必须是值类型。Nullable可以指定除-之外的任何值类型。有关更多信息，请参阅使用可空类型（C# 编程指南）。where T : class- 类型参数必须是引用类型；这也适用于任何类、接口、委托或数组类型。where T : new()- 类型参数必须有一个公共的无参数构造函数。当与其他约束一起使用时，new()必须最后指定约束。where T : <base class name>- 类型参数必须是或派生自指定的基类。where T : <interface name>- 类型参数必须是或实现指定的接口。可以指定多个接口约束。约束接口也可以是通用的。where T : U- 为 提供的类型参数T必须是或派生自为 提供的参数U。这称为裸类型约束。
These can also be linked together like this:
这些也可以像这样链接在一起：
C#
C＃
public class TestClass<T> where T : MyBaseClass, INotifyPropertyChanged, new() { }
public interface IGenericFace<T> where T : SomeBaseClass
VB
VB
Public Class TestClass(Of T As {MyBaseClass, INotifyPropertyChanged, New})
Public Interface IGenericInterface(Of T As SomeBaseClass)
