Umbraco-CMS/src/Umbraco.Core/ExpressionExtensions.cs

using System;
using System.Linq.Expressions;

namespace Umbraco.Core
{
    internal static class ExpressionExtensions
    {
        public static Expression<Func<T, bool>> True<T>() { return f => true; }

        public static Expression<Func<T, bool>> False<T>() { return f => false; }

        public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> left, Expression<Func<T, bool>> right)
        {
            var invokedExpr = Expression.Invoke(right, left.Parameters);
            return Expression.Lambda<Func<T, bool>>(Expression.OrElse(left.Body, invokedExpr), left.Parameters);
        }

        public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> left, Expression<Func<T, bool>> right)
        {
            var invokedExpr = Expression.Invoke(right, left.Parameters);
            return Expression.Lambda<Func<T, bool>> (Expression.AndAlso(left.Body, invokedExpr), left.Parameters);
        }
    }
}