Question

I wonder if its possible to remove all the objects from the same kind from a generic List using extension methods. something like this code:

public static Remove<T>(this List<[any type]> list)
{
    // some code to remove the objects of type T from the list
}

I can do this by using the following code:

public static Remove<T, K>(this List<K> list)
{
    // some code to remove the objects of type T from the List<K>
}

but I want to just use on type (T), without need to specify any type K. by doing that the user can use this extension method by simply write this:

List<object> list = new List<object>();
list.Add(1);
list.Add("text");

// remove all int type objects from the list
list.Remove<int>();

a extension method which I can use to do something exactly like the above code is what I really need here.

best regards

Answer 1

Not sure if this will work or not…but it’s worth a shot (I can’t compile to double check):

public static void Remove<T>(this IList list)
{
    if(list != null)
    {
        var toRemove = list.OfType<T>().ToList();

        foreach(var item in toRemove)
            list.Remove(item);
    }
}

Or if you need something a little more strict (rather than any object that can be cast to the type), you could try:

public static void Remove<T>(this IList list)
{
    if(list != null)
    {
        var toRemove = list.Where(i => typeof(i) == typeof(T)).ToList();

        foreach(var item in toRemove)
            list.Remove(item);
    }
}

In theory, you should be good to go. List<T> implements IList which implements IEnumerable. IList provides Remove() and IEnumerable provides the extension method.

Be aware that this could most definitely produce unexpected results depending on the types in the collection. I agree with Jon Skeet…it’s most definitely ugly.