Extensions to Func<T, bool> to allow composing predicate functions.

CompositePredicate.cs

using System;

namespace Fusion.Foundation.Specifications
{
    /// <summary>
    /// Adds extensions to allow composing predicates.
    /// </summary>
    public static class CompositePredicate
    {
        #region methods

        /// <summary>
        /// Composes the two predicate functions with an '&&'.
        /// </summary>
        /// <typeparam name="T">The type of the predicate function.</typeparam>
        /// <param name="left">The left.</param>
        /// <param name="right">The right.</param>
        /// <returns>The composed predicate function.</returns>
        public static Func<T, bool> And<T>(this Func<T, bool> left, Func<T, bool> right)
        {
            return target => left(target) && right(target);
        }

        /// <summary>
        /// Reverses boolean of the specified predicate.
        /// </summary>
        /// <typeparam name="T">The type of the predicate.</typeparam>
        /// <param name="predicate">The predicate.</param>
        /// <returns>The reversed predicate.</returns>
        public static Func<T, bool> Not<T>(this Func<T, bool> predicate)
        {
            return target => !predicate(target);
        }

        /// <summary>
        /// Composes the two predicate functions with an '&&'.
        /// </summary>
        /// <typeparam name="T">The type of the predicate function.</typeparam>
        /// <param name="left">The left.</param>
        /// <param name="right">The right.</param>
        /// <returns>The composed predicate function.</returns>
        public static Func<T, bool> Or<T>(this Func<T, bool> left, Func<T, bool> right)
        {
            return target => left(target) || right(target);
        }

        #endregion
    }
}