表达式树使用(一)

万物只要有开始，就必有结束

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Program.cs

   class Program
    {
        static void Main(string[] args)
        {
            
            Expression<Func<int, int, int>> expression = (a, b) => a + b;
            Console.WriteLine("这是表达式主体{0}", expression.Body);
            Console.WriteLine("这是实际表达式{0}", expression);
            //int d = expression(3, 5);
            Func<int, int, int> function = (a, b) => a + b;
            Func<int, int, bool> function2 = (a,b) => (a < b);
           
            Expression<Func<int, int, bool>> Expression2 = (a, b) => (a < b);
            Console.WriteLine("这是expression2的主体{0}", Expression2.Body);
            Expression<Func<int, bool>> lessThan = i => i < 5;
            Console.WriteLine(lessThan);
            Console.WriteLine("表达式的结果{0}  ", lessThan);
            Expression<Func<int, int>> plusEquals = (a) =>  (a+a);
            Console.WriteLine("这是plusEqual的主体{0}", plusEquals.Body);
            Console.WriteLine(plusEquals);
            //Int32 c = plusEquals(3);
            int c = plusEquals.Compile()(3);
            Console.WriteLine("这里是plusEquals表达式的结果{0}", c);
            //我想在这里做一个sql查询
            //var query = from cus in db.Customers where cus.City == "Nantes" select new { cus.City, cus.CompanyName };

            Console.ReadLine();
        }
    }

运行结果如图:

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