通用集合实例中的多类型约束

发布于 2024-10-15 03:25:53 字数 493 浏览 1 评论 0原文

我想实例化一个泛型集合（在本例中为字典），但在泛型类型声明中，我希望将参数类型限制为超过 1 个类。

这是示例代码：

我有很多带有此声明的类：

public class MyClass1 : UserControl, IEspecialOptions
public class MyClass2 : UserControl, IEspecialOptions, IOtherInterface

等等。

这就是我想要的：

Dictionary<int, T> where T:UserControl, IEspecialOptions myDicc = new Dictionary<int, T>();

这看起来非常好，但无法编译。

你知道如何限制第二个参数继承两个类/接口吗？

我仅限于 .net 2.0

提前致谢

原文

I want to instantiate a generic collection (a Dictionary in this case) but in the generic type declaration I want constraint the parameter type to more then 1 class.

Here is the example code:

I have many classes with this declaration:

public class MyClass1 : UserControl, IEspecialOptions
public class MyClass2 : UserControl, IEspecialOptions, IOtherInterface

etc.

This is what I want:

Dictionary<int, T> where T:UserControl, IEspecialOptions myDicc = new Dictionary<int, T>();

This looks very nice but don't compile.

Do you know how to contraint the second parameter to inherate from 2 classes/interfaces?

I'm limited to .net 2.0

Thanks in advance

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风流物 2024-10-22 03:25:53

你不能。但是您可以创建一个继承UserControl 并实现IEscpecialOptions 的抽象类，然后将泛型参数限制为抽象类型。

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塔塔猫 2024-10-22 03:25:53

您需要在引入 T 的方法或类级别指定约束，而不是在声明变量时指定。

class myDictClass<T> : where T:UserControl,IEspecialOPtions
{
  Dictionary<int,T> myDicc;
}

YOu need to specify the contraint at the method or class level that introduces T, not when declaring your variable.

class myDictClass<T> : where T:UserControl,IEspecialOPtions
{
  Dictionary<int,T> myDicc;
}

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天生の放荡 2024-10-22 03:25:53

只需创建一个 Dictionary 的自定义祖先即可引入约束。像这样：

public class CustomControlDictionary<TKey, TValue> : Dictionary<TKey, TValue>
    where TValue : UserControl, IEspecialOptions
{
    // possible constructors and custom methods, properties, etc.
}

然后您将能够按照您想要的方式在代码中使用它：

// this compiles:
CustomControlDictionary<int, MyClass1> dict1 = new CustomControlDictionary<int, MyClass1>();
CustomControlDictionary<int, MyClass2> dict2 = new CustomControlDictionary<int, MyClass2>();

// this fails to compile:
CustomControlDictionary<int, string> dict3 = ...;

如果示例中的类型参数 T 是从外部提供的，您必须很自然地引入类型约束在周围的班级水平。

public class MyCustomControlContainer<T> where T : UserControl, IEspecialOptions
{
    // this compiles:
    private CustomControlDictionary<int, T>;
}

注意：如果您想在同一字典中混合使用 MyClass1 和 MyClass2 实例，则必须为它们引入一个共同的祖先，继承自 UserControl 并实现IEspecialOptions。在这种情况下，抽象类是正确的方法。

Just make a custom ancestor of Dictionary<TKey,TValue> to introduce the constraint. Like this:

public class CustomControlDictionary<TKey, TValue> : Dictionary<TKey, TValue>
    where TValue : UserControl, IEspecialOptions
{
    // possible constructors and custom methods, properties, etc.
}

Then you will be able to use it in your code like you want:

// this compiles:
CustomControlDictionary<int, MyClass1> dict1 = new CustomControlDictionary<int, MyClass1>();
CustomControlDictionary<int, MyClass2> dict2 = new CustomControlDictionary<int, MyClass2>();

// this fails to compile:
CustomControlDictionary<int, string> dict3 = ...;

In case the type parameter T from your example is provided from outside, you have to, quite naturally, introduce the type constraint at the surrounding class level.

public class MyCustomControlContainer<T> where T : UserControl, IEspecialOptions
{
    // this compiles:
    private CustomControlDictionary<int, T>;
}

Note: In case you'd want to mix both MyClass1 and MyClass2 instances in the same dictionary, you'd have to introduce a common ancestor for them, inheriting from UserControl and implementing IEspecialOptions. An abstract class would be the right way in that case.

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