Maybe

MaybeExtensions.cs

    /// <summary>
    /// "Maybe" monad extension that make working with long chains of null
    /// checks easier. From http://www.codeproject.com/KB/cs/maybemonads.aspx.
    /// </summary>
    public static class MaybeExtensions
    {
        /// <summary>
        /// Executes the specified action if the input object is not null; otherwise, the action is not invoked.
        /// </summary>
        /// <typeparam name="TInput">The type of the object that is tested against null.</typeparam>
        /// <param name="obj">The object that is tested against null.</param>
        /// <param name="action">The action that is performed if the object is not null.</param>
        /// <returns>The object that was passed in.</returns>
        public static TInput Do<TInput>(this TInput obj, Action<TInput> action)
        {
            if (obj == null)
            {
                return default(TInput);
            }

            action(obj);

            return obj;
        }

        /// <summary>
        /// Returns the result of the evaluator expression if the input object
        /// is not null; otherwise, returns the failureValue.
        /// </summary>
        /// <typeparam name="TInput">The type of the object that is tested against null.</typeparam>
        /// <typeparam name="TResult">The type of the object that is returned.</typeparam>
        /// <param name="obj">The object that is tested against null.</param>
        /// <param name="evaluator">The evaluator function that is applied against the object if it is not null.</param>
        /// <param name="failureValue">The value that is returned instead if the object is null.</param>
        /// <returns>The result of the evaluator function or the failureValue as is appropriate.</returns>
        public static TResult Return<TInput, TResult>(
            this TInput obj,
            Func<TInput, TResult> evaluator,
            TResult failureValue)
        {
            if (obj == null)
            {
                return failureValue;
            }

            return evaluator(obj);
        }

        /// <summary>
        /// Returns the result of the evaluator function if the object to be
        /// tested is not null; otherwise, null.
        /// </summary>
        /// <typeparam name="TInput">The type of the object that is tested against null.</typeparam>
        /// <typeparam name="TResult">The type of the object that is returned.</typeparam>
        /// <param name="obj">The object that is tested against null.</param>
        /// <param name="evaluator">The evaluator function that is applied against the object if it is not null.</param>
        /// <returns>The result of the evaluator function if the object is not null; otherwise, null.</returns>
        public static TResult With<TInput, TResult>(
            this TInput obj,
            Func<TInput, TResult> evaluator)
        {
            if (obj == null)
            {
                return default(TResult);
            }

            return evaluator(obj);
        }
    }