Linq extensions

        public static class Linq
    {
        public static IEnumerable<T> Except<T>(this IEnumerable<T> source, IEnumerable<T> target, Func<T, T, bool> func)
        {
            return source.Except(target, new LambdaComparer<T>(func));
        }

        public static TResult With<TInput, TResult>(this TInput o, Func<TInput, TResult> evaluator)
            where TInput : class
        {
            if (o == null) return default(TResult);
            return evaluator(o);
        }

        public static TResult Return<TInput, TResult>(this TInput o, Func<TInput, TResult> evaluator, TResult failure_value) where TInput : class
        {
            if (o == null) return failure_value;
            return evaluator(o);
        }

        public static bool Check<TInput>(this TInput o, Func<TInput, bool> evaluator) where TInput : class
        {
            if (o == null) return false;
            return evaluator(o);
        }

        public static TInput If<TInput>(this TInput o, Func<TInput, bool> evaluator) where TInput : class
        {
            if (o == null) return null;
            return evaluator(o) ? o : null;
        }

        public static TInput Unless<TInput>(this TInput o, Func<TInput, bool> evaluator) where TInput : class
        {
            if (o == null) return null;
            return evaluator(o) ? null : o;
        }

        public static TInput Do<TInput>(this TInput o, Action<TInput> action) where TInput : class
        {
            if (o == null) return null;
            action(o);
            return o;
        }

        public static List<TInput> Delete<TInput>(this List<TInput> o, Func<TInput, bool> evaluator) where TInput : class
        {
            var listToDelete = o.Where(evaluator).ToList();
            foreach (var input in listToDelete)
            {
                o.Remove(input);
            }
            return o;
        }
    }
public class LambdaComparer<T> : IEqualityComparer<T>
    {
        private readonly Func<T, T, bool> _lambdaComparer;
        private readonly Func<T, int> _lambdaHash;

        public LambdaComparer(Func<T, T, bool> lambdaComparer) :
            this(lambdaComparer, o => 0)
        {
        }

        public LambdaComparer(Func<T, T, bool> lambdaComparer, Func<T, int> lambdaHash)
        {
            if (lambdaComparer == null)
                throw new ArgumentNullException("lambdaComparer");
            if (lambdaHash == null)
                throw new ArgumentNullException("lambdaHash");

            _lambdaComparer = lambdaComparer;
            _lambdaHash = lambdaHash;
        }

        public bool Equals(T x, T y)
        {
            return _lambdaComparer(x, y);
        }

        public int GetHashCode(T obj)
        {
            return _lambdaHash(obj);
        }
    }