Foreach List with unknown item type

I need to go through List. I do not know in advance what type of element List contains the List I get as an object.

void anyMethod(object listData, Func<object, string> callback)
{
    foreach (object item in (List<object>)data)
    {
        string value = callback(item);
        doSomethi开发者_开发百科ng(value)
    }
};
...
List<MyObject> myList = something();
anyMethod(myList, obj => (MyObject)obj.Name)
...
List<AnotherObject> myList = somethingAnother();
anyMethod(myList, obj => (AnotherObject)obj.foo + (AnotherObject)obj.bar)
...

I need something he does as DropDownList when the process DataSource. Thanks for your help.

You could try this:

void anyMethod(object listData, Func<object, string> callback)
{
    IEnumerable enumerable = listData as IEnumerable;
    if(enumerable == null)
        throw new InvalidOperationException("listData mist be enumerable");
    foreach (object item in enumerable.OfType<object>())
    {
        string value = callback(item);
        doSomething(value)
    }
};

However, if you actually call this method with a strongly typed list (such as List<YourType>) you can use generics better:

void anyMethod<T>(IEnumerable<T> listData, Func<T, string> callback)
{
    foreach (T item in listData)
    {
        string value = callback(item);
        doSomething(value)
    }
};

which is a lot cleaner.

If DoSomething() is a static method, you can use a generic extension method (as List<T> itself is generic anyway):

public static void AnyMethod<T>(this List<T> listData, Func<T, string> callback)
{
    foreach (T item in listData)
    {
        string value = callback(item);
        DoSomething(value);
    }
}

Then call it like this:

List<MyObject> myList = Something();
myList.AnyMethod(obj => obj.Name);

List<AnotherObject> myList = SomethingAnother();
myList.AnyMethod(obj => obj.foo + obj.bar);

Notice you do not need to cast either.

However, if DoSomething() is an instance method, I think you can go with Jamiec's second solution.