通过仅了解类的类型来获取类的类型参数 [英] Get the type parameter of a Class, by knowing only the Type of Class

问题描述

我有一个基础抽象类，它具有另一个抽象类的类型参数，例如:

I have a base abstract class having a type parameter from another abstract class, as:

public abstract class Database<T> where T : DatabaseItem, new() { //... }

public abstract class DatabaseItem { //... }

然后我有一些固有的子类:

Then I have number of children classes inherent from it:

public class ShopDatabase : Database<ShopItem> {}
public class ShopItem : DatabaseItem {}

public class WeaponDatabase : Database<WeaponItem> {}
public class WeaponItem : DatabaseItem {}

//...

现在的问题是，我有一个数据库的 Type 数组:

Now the problem is, I have an array of Type of Database as:

private static readonly Type[] DATABASE_TYPES = new Type[] {
    typeof (ShopDatabase),
    typeof (WeaponDatabase)
};

我想将所有类型参数作为另一个数组获取，像这样:

And I want to get all their type parameters as another array, something like this:

Type[] databaseItemTypes = MyFunction (DATABASE_TYPES);
// databaseItemTypes will be an array as: [ShopDatabaseItem, WeaponDatabaseItem]

它可能类似于以下问题但我什至没有Class的实例，所以...

It may be similar to this question but I don't even have a instance of the Class, so...

推荐答案

如果您要查找特定类的类型参数，那么相对容易:

If you're looking for the type arguments for a specific class, that's relatively easy:

static Type GetDatabaseTypeArgument(Type type)
{
    for (Type current = type; current != null; current = current.BaseType)
    {
        if (current.IsGenericType && current.GetGenericTypeDefinition() == typeof(Database<>))
        {
            return current.GetGenericTypeArguments()[0];
        }
    }
    throw new ArgumentException("Type incompatible with Database<T>");
}

然后您可以使用:

Type[] databaseItemTypes = DatabaseTypes.Select(GetDatabaseTypeArgument).ToArray();

请注意，如果您有以下课程:

Note that if you have a class of:

public class Foo<T> : Database<T>

...然后您将最终获得一个 Type 引用，该引用表示 Foo< T> 中的 T .例如，对于基本类型为 Foo< string> 的类型，要摆脱这种情况将很棘手.希望你不在那种情况下...

... then you'll end up getting a Type reference representing the T in Foo<T>. Getting rid of that for a type with a base type of Foo<string> for example would be tricky. Hopefully you're not in that situation...

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