我如何检测的对象是一个泛型集合，它包含什么类型的？ [英] How do I detect that an object is a generic collection, and what types it contains?

问题描述

我有一个字符串序列化的实用工具，需要的（几乎）所有类型的变量，并将其转换成一个字符串。因此，例如，根据我的约定，123的整数值将被序列为i：3：123。（ⅰ=整数; 3 =长度字符串; 123 =值）

I have a string serialization utility that takes a variable of (almost) any type and converts it into a string. Thus, for example, according to my convention, an integer value of 123 would be serialized as "i:3:123" (i=integer; 3=length of string; 123=value).

该实用程序处理所有的基本类型，以及一些非泛型集合一样的ArrayList和哈希表。接口的形式的

The utility handles all primitive type, as well as some non-generic collections, like ArrayLists and Hashtables. The interface is of the form

公共静态字符串StringSerialize（对象o）{}

和内部检测我什么类型的对象，并相应地对其进行序列化。

and internally I detect what type the object is and serialize it accordingly.

现在我想升级我的程序来处理泛型集合。有趣的是，我无法找到一个合适的函数来检测的对象是一个泛型集合，它包含哪些类型 - 这两者的信息片段，我需要以正确序列化。至今我一直在使用形式编码

Now I want to upgrade my utility to handle generic collections. The funny thing is, I can't find an appropriate function to detect that the object is a generic collection, and what types it contains - both of which pieces of information I need in order to serialize it correctly. To date I've been using coding of the form

如果（邻为int）{//做一些事情}

但似乎并没有泛型工作。

but that doesn't seem to work with generics.

你有什么建议？

---

编辑：感谢<一个href=\"http://stackoverflow.com/questions/755200/how-do-i-detect-that-an-object-is-a-generic-collection-and-what-types-it-contain/755217#755217\">Lucero,我已经得到接近答案，但我被困在这个小语法难题在这里：

Thanks to Lucero, I've gotten closer to the answer, but I'm stuck at this little syntactical conundrum here:

if (t.IsGenericType) {
  if (typeof(List<>) == t.GetGenericTypeDefinition()) {
    Type lt = t.GetGenericArguments()[0];
    List<lt> x = (List<lt>)o;
    stringifyList(x);
  }
}

这code不能编译，因为 LT 是不允许的＆LT; T＆GT; A 名单，LT的说法;＆GT; 对象。为什么不？什么是正确的语法？

This code doesn't compile, because "lt" is not allowed as the <T> argument of a List<> object. Why not? And what is the correct syntax?

推荐答案

重新您的难题;我假设 stringifyList 是一个通用的方法是什么？您需要使用反射来调用它：

Re your conundrum; I'm assuming stringifyList is a generic method? You would need to invoke it with reflection:

MethodInfo method = typeof(SomeType).GetMethod("stringifyList")
            .MakeGenericMethod(lt).Invoke({target}, new object[] {o});

其中， {目标} 是空的静态方法，或这个对当前实例的实例方法。

where {target} is null for a static method, or this for an instance method on the current instance.

另外 - 我不认为所有的藏品是：根据列表＆LT; T＆GT; ，B：泛型类型。最重要的是：？他们实施的IList＆LT; T＆GT; 一些 T

Further - I wouldn't assume that all collections are a: based on List<T>, b: generic types. The important thing is: do they implement IList<T> for some T?

下面是一个完整的例子：

Here's a complete example:

using System;
using System.Collections.Generic;
static class Program {
    static Type GetListType(Type type) {
        foreach (Type intType in type.GetInterfaces()) {
            if (intType.IsGenericType
                && intType.GetGenericTypeDefinition() == typeof(IList<>)) {
                return intType.GetGenericArguments()[0];
            }
        }
        return null;
    }
    static void Main() {
        object o = new List<int> { 1, 2, 3, 4, 5 };
        Type t = o.GetType();
        Type lt = GetListType(t);
        if (lt != null) {
            typeof(Program).GetMethod("StringifyList")
                .MakeGenericMethod(lt).Invoke(null,
                new object[] { o });
        }
    }
    public static void StringifyList<T>(IList<T> list) {
        Console.WriteLine("Working with " + typeof(T).Name);
    }
}

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