Accessing object's property inside generic method [duplicate]

Question

How can access the property of an object inside generic method?
I can't use where T: A because this method will receive different objects, but all objects have a common property to work on.
(I also can't make for them a common interface)

public class A
{
    public int Number {get;set;}
}


List<A> listA = new List<A>{
                new A {Number =4},
                new A {Number =1},
                new A {Number =5}
};

Work<A>(listA);

public static void Work<T>(List<T> list1)
{
    foreach(T item in list1)
    {
        do something with item.Number;
    }
}

An update: I need also to set the property

Answer 1

You have a few choices:

• Make a common interface.
• Use reflection.
• Use the dynamic type in .NET 4.

I know you said you can't do the first, but it's the best option for performance and maintainability so please reconsider if its possible before choosing one of the other methods. Remember that even if you can't modify the original code you might still be able to choose the first option. For example if your classes are partial classes you can implement the interface in another file:

File 1:

// Automatically generated code that you can't change.
partial class A
{
    public int Number { get; set; }
}

File 2:

interface IHasNumber
{
    int Number { get; set; }
}

partial class A : IHasNumber
{
}

If the original class isn't defined as partial you could write wrapper classes around them that implement the interface.

Once you have the common interface you can change your generic constraint to require this interface:

where T : IHasNumber

Answer 2

If you don't need the list - just the items, I would use a projection outside the method:

static void Main()
{
    List<A> listA = new List<A>{
            new A {Number =4},
            new A {Number =1},
            new A {Number =5}
    };

    Work(listA.Select(a => a.Number));

}
public static void Work(IEnumerable<int> items)
{
    foreach (number item in items)
    {
        // do something with number;
    }
}

If you need the list - a projection inside the method via a selector:

static void Main()
{
    List<A> listA = new List<A>{
            new A {Number =4},
            new A {Number =1},
            new A {Number =5}
    };

    Work(listA, a => a.Number);

}
public static void Work<T>(IList<T> list, Func<T, int> selector)
{
    foreach (T obj in list)
    {
        int number = selector(obj);
        // do something with number;
    }
}