C# 获取泛型类的属性

Get property of generic class

提问by gunr2171

I have a generic class, and an object value where obj.GetType().GetGenericTypeDefinition() == typeof(Foo<>).

我有一个通用类和一个对象值，其中obj.GetType().GetGenericTypeDefinition() == typeof(Foo<>).

class Foo<T>
{
    public List<T> Items { get; set; }
}

How do I get the value of Itemsfrom obj? Remember, objis an Object, I can't cast objas Foobecause I don't know what Tis.

我如何获得Itemsfrom的值obj？请记住，obj是Object，我不能转换obj为 asFoo因为我不知道是什么T。

I was hoping to use reflection for this, but each time I do GetProperty("Items")it returns null. However, if someone knows a good way to do this without reflection, by all means.

我希望为此使用反射，但每次我这样做GetProperty("Items")都会返回 null。但是，如果有人知道一种无需反思就可以做到这一点的好方法，那么无论如何。

Let's say my code looks like this:

假设我的代码如下所示：

//just to demonstrate where this comes from
Foo<int> fooObject = new Foo<int>();
fooObject.Items = someList;
object obj = (object)fooObject;

//now trying to get the Item value back from obj
//assume I have no idea what <T> is
PropertyInfo propInfo = obj.GetType().GetProperty("Items"); //this returns null
object itemValue = propInfo.GetValue(obj, null); //and this breaks because it's null

采纳答案by Reed Copsey

You should be able to use:

您应该能够使用：

Type t = obj.GetType();

PropertyInfo prop = t.GetProperty("Items");

object list = prop.GetValue(obj);

You will not be able to cast as a List<T>directly, of course, as you don't know the type T, but you should still be able to get the value of Items.

List<T>当然，您将无法直接转换为 a ，因为您不知道 type T，但您仍然应该能够获得Items.

---

---

Edit:

编辑：

The following is a complete example, to demonstrate this working:

以下是一个完整的示例，用于演示此工作：

// Define other methods and classes here
class Foo<T>
{
    public List<T> Items { get; set; }
}

class Program
{
    void Main()
    {   
        //just to demonstrate where this comes from
        Foo<int> fooObject = new Foo<int>();
        fooObject.Items = new List<int> { 1, 2, 3};
        object obj = (object)fooObject;

        //now trying to get the Item value back from obj
        //assume I have no idea what <T> is
        PropertyInfo propInfo = obj.GetType().GetProperty("Items"); //this returns null
        object itemValue = propInfo.GetValue(obj, null);

        Console.WriteLine(itemValue);
                    // Does not print out NULL - prints out System.Collections.Generic.List`1[System.Int32]


        IList values = (IList)itemValue;
        foreach(var val in values)
            Console.WriteLine(val); // Writes out values appropriately
    }
}

回答by sa_ddam213

Something like this should do the trick:

像这样的事情应该可以解决问题：

var foo = new Foo<int>();
foo.Items = new List<int>(new int[]{1,2,3});

// this check is probably not needed, but safety first :)
if (foo.GetType().GetProperties().Any(p => p.Name == "Items"))
{
    var items = foo.GetType().GetProperty("Items").GetValue(foo, null);
}

回答by JerKimball

@ReedCopsey is absolutely correct, but in case you're really asking the question "How do I fish out the generic details of a type?", here's some "Fun with Reflection":

@ReedCopsey 是绝对正确的，但如果您真的问“我如何找出类型的通用细节？”的问题，这里有一些“有趣的反射”：

public void WhatsaFoo(object obj)
{
    var genericType = obj.GetType().GetGenericTypeDefinition();
    if(genericType == typeof(Foo<>))
    {
        // Figure out what generic args were used to make this thing
        var genArgs = obj.GetType().GetGenericArguments();

        // fetch the actual typed variant of Foo
        var typedVariant = genericType.MakeGenericType(genArgs);

        // alternatively, we can say what the type of T is...
        var typeofT = obj.GetType().GetGenericArguments().First();

        // or fetch the list...
        var itemsOf = typedVariant.GetProperty("Items").GetValue(obj, null);
    }
}

回答by vibs2006

You have to use System.Reflectionnamespace to execute the program successfully.

您必须使用System.Reflection命名空间才能成功执行程序。

This program gives you Property Name and Value of any Generic Class

该程序为您提供任何通用类的属性名称和值

You can check this code fiddle on C# Online Rexter Tool Compilerat

您可以检查这些代码的小提琴C＃在线Rexter工具编译器在

using System;
using System.Reflection;

namespace GenericPropertyExample
{
    //Declaring a Sample Class 
    public class class1
    {
        public string prop1 { get; set; }
        public string prop2 { get; set; }

    }
    public class Program
    {
        public static void Main(string[] args)
        {
            //Creating Class Object
            class1 objClass1 = new class1 { prop1 = "value1", prop2 = "value2" };

            //Passing Class Object to GenericPropertyFinder Class
            GenericPropertyFinder<class1> objGenericPropertyFinder = new GenericPropertyFinder<class1>();
            objGenericPropertyFinder.PrintTModelPropertyAndValue(objClass1);
            Console.ReadLine();
        }

        //Declaring a Generic Handler Class which will actually give Property Name,Value for any given class.
        public class GenericPropertyFinder<TModel> where TModel : class
        {
            public void PrintTModelPropertyAndValue(TModel tmodelObj)
            {
                //Getting Type of Generic Class Model
                Type tModelType = tmodelObj.GetType();

                //We will be defining a PropertyInfo Object which contains details about the class property 
                PropertyInfo[] arrayPropertyInfos = tModelType.GetProperties();

                //Now we will loop in all properties one by one to get value
                foreach (PropertyInfo property in arrayPropertyInfos)
                {
                    Console.WriteLine("Name of Property is\t:\t" + property.Name);
                    Console.WriteLine("Value of Property is\t:\t" + property.GetValue(tmodelObj).ToString());
                    Console.WriteLine(Environment.NewLine);
                }
            }
        }
    }
}

回答by René Mouritsen

Hey guys ive been struggeling with the same issue with generic typs and finally found the solution that gets the value --------Small code snippet of the method that does the trick ------------------

嘿伙计们，我一直在努力解决与通用类型相同的问题，终于找到了获取值的解决方案 -------- 可以解决问题的方法的小代码片段 ----------- -------

    public void printFields()
    {
        // Is the list empty
        if (this.list_.Count == 0)
        {
            //Y => Forced exit no object info
            return;
        }

        try
        {
            // Get first item from list
            T item = this.list_[0];

            // Get the type of object
            //**Type thisType = item.GetType();

            // Get array of all fields
            FieldInfo[] thisFieldInfo = item.GetType().GetFields(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);

            // Loop through all fields and show its info
            for (int ix = 0; ix < thisFieldInfo.Length; ix++)
            {
                // Get Field value
                String strVal = thisFieldInfo[ix].GetValue(item).ToString();

                // Display item
                Console.WriteLine("'{0}' is a {1} and has value {2}", thisFieldInfo[ix].Name, thisFieldInfo[ix].FieldType, strVal);
            }


        }
        catch (SecurityException e)
        {
            Console.WriteLine("Exception: " + e.Message);
        }
    }