Extension Method : Filtering & Casting a list based on an Interface: c# extension methods

Extension Method : Filtering & Casting a list based on an Interface

Dear Experts,

I'm mighty stuck, any clues on how i can make the below code work?

If not any other ideas on getting around this?
Note that where i'm using this code, I have a List<K> where the list contains a number of classes which are subclasses of an abstract class K, i want to filter out a particular selection of these classes by the interfaces they implement.

Many thanks

David

P>S> are there any repositories of Extension Methods - i'm sure this is re-inventing the wheel...

/// <summary>
        /// Filter a List of objects on whether they implement a given interface - and then cast them to that interface 
        /// </summary>
        /// <typeparam name="K">Type of the list</typeparam>
        /// <typeparam name="I">Interface to filter by and cast to</typeparam>
        /// <param name="list">List to filter</param>
        /// <returns>List of objects which implement interface I cast to I</returns>
        public static List<I> FilterAndCastTo<K,I>(this IEnumerable<K> list ) {
            List<I> res = new List<I>();
            foreach (K k in list) {
                if (k.GetType().GetInterfaces().Contains(typeof(I))) {
                    res.Add((I) k); /// <<<< THIS BREAKS :[ 
                }
            }
            return res;
        }

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/// <summary> /// Filter a List of objects on whether they implement a given interface - and then cast to that interface /// </summary> /// <typeparam name="K">Type of the list</typeparam> /// <typeparam name="I">Interface to filter by and cast to</typeparam> /// <param name="list">List to filter</param> /// <returns>List of objects which implement interface I cast to I</returns> public static List<I> FilterAndCastTo<K,I>(this IEnumerable<K> list )where I : class { List<I> res = new List<I>(); foreach (K k in list) { I i = k as I; if (i != null) { res.Add(i); } } return res; }

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Extension Method : Filtering & Casting a list based on an Interface

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