将IsConstructedGenericType永远是IsGenericTypeDefinition的否定，对一个泛型类型？ [英] Will IsConstructedGenericType always be the negation of IsGenericTypeDefinition, for a generic type?

问题描述

在实例属​​性的<一个文档href="http://msdn.microsoft.com/en-us/library/system.type.isconstructedgenerictype.aspx"><$c$c>Type.IsConstructedGenericType不清楚或误导性的。

The documentation of the instance property Type.IsConstructedGenericType is unclear or misleading.

我尝试以下code找到这个实际行为与相关属性：

I tried the following code to find the actual behavior of this and related properties:

// create list of types to use later in a Dictionary<,>
var li = new List<Type>();

// two concrete types:
li.Add(typeof(int));
li.Add(typeof(string));

// the two type parameters from Dictionary<,>
li.Add(typeof(Dictionary<,>).GetGenericArguments()[0]);
li.Add(typeof(Dictionary<,>).GetGenericArguments()[1]);

// two unrelated type parameters
li.Add(typeof(Func<,,,>).GetGenericArguments()[1]);
li.Add(typeof(EventHandler<>).GetGenericArguments()[0]);

// run through all possibilities
foreach (var first in li)
{
    foreach (var second in li)
    {
        var t = typeof(Dictionary<,>).MakeGenericType(first, second);
        Console.WriteLine(t);
        Console.WriteLine(t.IsGenericTypeDefinition);
        Console.WriteLine(t.IsConstructedGenericType);
        Console.WriteLine(t.ContainsGenericParameters);
    }
}

在code通过笛卡尔积组成的36种 T 。

结果：32种（所有，但4种组合词典＆LT; INT，INT＆GT; ，词典＆LT; INT，字符串＆GT; ，词典＆LT;字符串，INT＆GT; ，词典＆LT;字符串，字符串＆GT; ）的值 ContainsGenericParameters 是真实的。

Results: For 32 types (all but the 4 combinations Dictionary<int, int>, Dictionary<int, string>, Dictionary<string, int>, Dictionary<string, string>), the value of ContainsGenericParameters was true.

有关35种， IsGenericTypeDefinition 是假的，而 IsConstructedGenericType 是真实的。对于最后一种，即（不出所料）：

For 35 types, IsGenericTypeDefinition was false while IsConstructedGenericType was true. For the last type, namely (unsurprisingly):

System.Collections.Generic.Dictionary`2[TKey,TValue]

在 IsGenericTypeDefinition 是真实的 IsConstructedGenericType 是假的。

我可以断定，对于一个泛型类型，值 IsConstructedGenericType 总是 IsGenericTypeDefinition ？

Can I conclude that, for a generic type, the value of IsConstructedGenericType is always the opposite (negation) of IsGenericTypeDefinition?

（文档似乎宣称 IsConstructedGenericType 的而不是 ContainsGenericParameters 相反的，但我们清楚地展示了很多对反例的。）

(The documentation seems to claim that IsConstructedGenericType is instead the opposite of ContainsGenericParameters, but we clearly exhibited a lot of counterexamples to that.)

推荐答案

是的，这是正确的。假设键入的问题是一个泛型类型，完全 IsGenericTypeDefinition 中的一个或 IsConstructedGenericType 是真实的。我们可以很容易地从参考源为 RuntimeType （这是具体落实<$ C $的C>键入你的时候，你得到的GetType（）或 typeof运算）为什么是这样的情况：

Yes this is correct. Assuming that the Type in question is a generic type, exactly one of IsGenericTypeDefinition or IsConstructedGenericType is true. We can easily from the reference source for RuntimeType (which is the concrete implementation of Type you get when you do GetType() or typeof) why this is the case:

public override bool IsConstructedGenericType 
{
    get { return IsGenericType && !IsGenericTypeDefinition; } 
} 

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