Lambda表达式树

        static void Main(string[] args)
        {
            var ints = new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
            ParameterExpression parameter = Expression.Parameter(typeof(Int32));
            BinaryExpression condition = null;
            //要构造的表达式i==1||i==2||i==3.....
            for (int i = 0; i < ints.Length; i++)
            {
                ConstantExpression ce = Expression.Constant(i);
                if (condition == null)
                {
                    condition = Expression.Equal(parameter, ce);
                }
                else
                {
                    var right = Expression.Equal(parameter, ce);
                    condition = Expression.Or(condition, right);
                }
            }
            Expression<Func<Int32, Boolean>> lambda = Expression.Lambda<Func<Int32, Boolean>>(condition, parameter);
            foreach (var item in ints.Where(lambda.Compile()).ToList())
            {
                Console.WriteLine(item);
            }

            //p => p.Name == "1" && p.Address == "2"
            ParameterExpression parameter1 = Expression.Parameter(typeof(Person), "p");
            ConstantExpression constant1 = Expression.Constant("1");
            ConstantExpression constant2 = Expression.Constant("1");
            MemberExpression member = Expression.PropertyOrField(parameter1, "Name");
            var query1 = Expression.Equal(member, constant1);
            var query2 = Expression.Equal(Expression.PropertyOrField(parameter1, "Address"), constant2);
            var query = Expression.And(query1, query2);
            var lambda1 = Expression.Lambda<Func<Person, Boolean>>(query, parameter1);
            var list = MethodExtend.GetUser(lambda1.Compile());
            foreach (var item in list)
            {
                Console.WriteLine(item.Name + " " + item.Address);
            }
        }

新了解到linq表达式树，所以在此做备份，以防遗忘！