如何获取列表中元素的类型 [英] How to obtain type of an elements in list

问题描述

请你建议



我有未知类型的元素列表...比如， Type = typeof（List< ; of_something>）



如何确定它是否是List<>的类型或数组

如何确定所包含元素的类型 - 即 typeof（of_something）



谢谢你转发建议



我尝试过：



我不喜欢我知道如何实现这个

我被困了

Could you please suggest

I have TYPE of list of an elements of "unknown" type ... say, the Type = typeof(List<of_something>)

how to determine whether it's a type of List<> or Array
how to determine the type of an elements included - that is typeof(of_something)

thank you forward for advice

What I have tried:

I don't have an idea how to implement this
I am stuck

推荐答案

是的，你可以做到。

尝试以下扩展方法：

Yes, you can do it.
Try these extension methods:

public static class Extensions
    {
    public static Type GetContainedType<T>(this List<T> ls)
        {
        return typeof(T);
        }
    public static Type GetContainedType(this Array ar)
        {
        return ar.GetType().GetElementType();
        }
    }

然后你可以在你的收藏中调用它们：

You can then call them on your collections:

List<string> sl = new List<string>();
string[] sa = new string[10];
List<int> il = new List<int>();
int[] ia = new int[10];
Type tsl = sl.GetContainedType();
Type tsa = sa.GetContainedType();
Type til = il.GetContainedType();
Type tia = ia.GetContainedType();

嗨！



我假设是这样的：

Hi!

I supposed something like that:

class Program
{
    static void Main(string[] args)
    {
        Type t = (new List<MyType>() {new MyType(), new MyType(), new MyType() }).GetType();    //this is just for pupose of getting TYPE of List<string>
        //at this position we are interested in Type, not object itself

        //there is no object - just "Type" or PropertyInfo

        TypeInfo pi = t.GetTypeInfo();
        PropertyInfo prop = pi.DeclaredProperties.Where(c => c.Name == "Item").FirstOrDefault();
        Type tp = prop.PropertyType;
        object obj = tp.InvokeMember("", BindingFlags.CreateInstance, null, null, null);
        //now I need to cast the obj to the appropriate type to call the method Name()
    }
}

class MyType
{
    public string Name()
    {
        return "It's me";
    }
}

现在我需要将obj转换为合适的类型调用方法Name（）

class Program
    {
        static void Main(string[] args)
        {
            Type t = (new List<MyType>() {new MyType("1"), new MyType("2"), new MyType("3") }).GetType();    //this is just for pupose of getting TYPE of List<string>
            //at this position we are interested in Type, not object itself
            //this is no object - just "Type" or PropertyInfo
            TypeInfo pi = t.GetTypeInfo();
            PropertyInfo prop = pi.DeclaredProperties.Where(c => c.Name == "Item").FirstOrDefault(); //no matter how much objects were built and included in List (again - there is no object - just TYPE)
            Type tp = prop.PropertyType;
            object obj = tp.InvokeMember("", BindingFlags.CreateInstance, null, null, new object[] { "from Invoke" });

            //now we need to cast the obj to the appropriate type to call the method Name()

            object name = tp.InvokeMember("Name", BindingFlags.InvokeMethod, null, obj, null);
            //on my opinion there is just one way to invoke inner method without casting an object "obj" to the type "tp"
            //but still it would be better to obtain an object "obj" of properly type.
        }
    }

    class MyType
    {
        public MyType()
        {
            Console.Write("I was born => my name is: ");
        }

        public MyType(string s) : this()
        {
            Console.WriteLine(s);
        }

        public string Name()
        {
            return "It's me " ;
        }
    }

我认为只有一种方法可以调用内部方法而无需投射一个对象obj到类型tp

但仍然最好获得一个正确类型的对象obj。

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