表达式:使用API创建表达式树(4)DynamicExpression

DynamicExpression:表示动态操作。这个网上可见的资料少得可怜,但想到MVC和第三方的动态语言能在NET运行。好奇的倒腾了下

先声明两个类(有相同的方法和字段,但不是继承于同一接口的类),设想是动态调用它们的方法和字段。

表达式:使用API创建表达式树(4)DynamicExpression
    class AiTestD
        {
            public string Name = "你好!这是 AiTestD";
            public int Id = 123;
            public static string AiTest(string ai1, string ai2)
            {
                return ai1 + ai2;
            }

            public static int add(int a, int b)
            {

                return a + b;
            }

            public int add2(int a, int b)
            {

                return -(a + b);
            }
        }

        class AiTestD2
        {
            public string Name = "你好!这是 AiTestD2";
            public int Id = 789;
            public static string AiTest(string ai1, string ai2)
            {
                return "**" + ai1 + ai2;
            }
            public static int add(int a, int b)
            {
                return (a + b) * 1000;
            }
            public int add2(int a, int b)
            {
                return -(a + b) * 1000;
            }
        }
表达式:使用API创建表达式树(4)DynamicExpression

第一个方法 AiDynamicDo,要实现的是获取两个类的Id属性质(这里是值类型操作,刚开始时,定义的是typeof(Func<CallSite, object, int>,总是编译不过,发现在 Expression.MakeDynamic 中的参数,只要是值类型都是通不过的,只有通过Expression.Convert转换成 typeof(object),才可以,但引用类型是不用转换的)

 

表达式:使用API创建表达式树(4)DynamicExpression
        /// <summary>
        /// 获取字段
        /// </summary>
        /// <param name="aiD"></param>
        static void AiDynamicDo(dynamic aiD)
        {
            //声明参数
            ParameterExpression paramExpr = Expression.Parameter(typeof(object), "o");
            //获取 CallSite 以支持调用时的运行时。
            //CallSiteBinder 是必需的
        //注意这里用的是     Binder.GetMember    
        CallSiteBinder aiBinder = Binder.GetMember(CSharpBinderFlags.None, "Id", typeof(Program),
                new CSharpArgumentInfo[] { CSharpArgumentInfo.Create(CSharpArgumentInfoFlags.None, null) });
            //定义一个动态表达式
            //Func<CallSite, object, object>声明方式中 CallSite 是动态调用站点的基类。 此类型用作动态站点目标的参数类型。
            //就是上面的 aiBinder,第二个参数是要传入的动态类型 用dynamic关键字也是可以的,
            //后面的参数是实际调用和返回的参数
            //不过操作中发现在返回值一定要用 object 不然会编译不过
            //当然也可用Action<CallSite, object,...>,除了没返回值,参数要求和用Func<CallSite, object, object>是一样的。
           
            DynamicExpression Dynamic2 =
              Expression.MakeDynamic(typeof(Func<CallSite, object, object>),
                 aiBinder, paramExpr
          );
            //编译
            LambdaExpression laExp = Expression.Lambda(
                Expression.Block(
                new ParameterExpression[] { paramExpr },
                Expression.Assign(paramExpr, Expression.Constant(aiD))
              , Dynamic2));
            //执行
            Console.WriteLine("AiDynamicDo:" + laExp.ToString());
            Console.WriteLine("结果:" + laExp.Compile().DynamicInvoke());
            Console.WriteLine();

        }
表达式:使用API创建表达式树(4)DynamicExpression

调用:    

      AiDynamicDo(new AiTestD());

      AiDynamicDo(new AiTestD2());


输出为:
      AiDynamicDo:() => {var o; ... }
        结果:123

        AiDynamicDo:() => {var o; ... }
        结果:789

表达式:使用API创建表达式树(4)DynamicExpression
    /// <summary>
        /// 字段2
        /// </summary>
        /// <param name="aiD"></param>
        static void AiDynamicDo2(dynamic aiD)
        {
            //Binder.Convert
            CallSiteBinder aiBinder = Binder.Convert(CSharpBinderFlags.None, typeof(object), typeof(Program));
            ParameterExpression paramExpr = Expression.Parameter(aiD.GetType(), "o");
            MemberExpression namePropExpr = Expression.Field(paramExpr, "Name");
            var Dynamic2 = Expression.MakeDynamic(typeof(Func<CallSite, object, object>)
                , aiBinder
                , namePropExpr
          );
            LambdaExpression laExp = Expression.Lambda(
              Expression.Block(
              new ParameterExpression[] { paramExpr },
              Expression.Block(Expression.Assign(paramExpr, Expression.Constant(aiD))
              )
             , Dynamic2));
            Console.WriteLine("AiDynamicDo2:" + laExp.ToString());
            Console.WriteLine("结果:" + laExp.Compile().DynamicInvoke());
            Console.WriteLine();
        }

        /// <summary>
        /// 引用类型方法调用测试 Binder.Convert
        /// </summary>
        /// <param name="aiD"></param>
        static void AiDynamicDo3(dynamic aiD)
        {
            //Binder.Convert
            CallSiteBinder aiBinder = Binder.Convert(CSharpBinderFlags.None, typeof(object), typeof(Program));
            ParameterExpression aiParamExpr = Expression.Parameter(aiD.GetType(), "o");
            ParameterExpression aiParamExpr1 = Expression.Parameter(typeof(string), "a");
            ParameterExpression aiParamExpr2 = Expression.Parameter(typeof(string), "b");
            MethodCallExpression aiMth = Expression.Call(
                null, aiD.GetType().GetMethod("AiTest", new Type[] { typeof(string), typeof(string) }), aiParamExpr1, aiParamExpr2);
            var Dynamic2 =
              Expression.MakeDynamic(
              typeof(Func<CallSite, dynamic, object>),
              aiBinder, aiMth

          );
            LambdaExpression laExp = Expression.Lambda(Dynamic2, aiParamExpr1, aiParamExpr2);
            Console.WriteLine("AiDynamicDo3:" + laExp.ToString());
            Console.WriteLine("结果:" + laExp.Compile().DynamicInvoke("AiTest-", "动态调用"));
            Console.WriteLine();
        }

        /// <summary>
        /// 值类型方法调用测试 Binder.Convert
        /// </summary>
        /// <param name="aiD"></param>
        static void AiDynamicDo4(dynamic aiD)
        {
            CallSiteBinder aiBinder = Binder.Convert(CSharpBinderFlags.None, typeof(object), typeof(Program));
            ParameterExpression aiParamExpr = Expression.Parameter(aiD.GetType(), "o");
            ParameterExpression aiParamExpr1 = Expression.Parameter(typeof(int), "a");
            ParameterExpression aiParamExpr2 = Expression.Parameter(typeof(int), "b");

            MethodCallExpression aiMth = Expression.Call(
                null, aiD.GetType().GetMethod("add", new Type[] { typeof(int), typeof(int) }), aiParamExpr1, aiParamExpr2);
            var Dynamic2 =
              Expression.MakeDynamic(
              typeof(Func<CallSite, dynamic, object>),
             aiBinder,
              Expression.Convert(aiMth, typeof(object)) //!!这里要转换,否刚不能通过

          );
            //LambdaExpression laExp = Expression.Lambda(Dynamic2, paramExpr1, paramExpr2);
            LambdaExpression laExp = Expression.Lambda(
                 Expression.Block(
                new ParameterExpression[] { aiParamExpr1, aiParamExpr2 },
                Expression.Block(Expression.Assign(aiParamExpr1, Expression.Constant(30)),
                Expression.Assign(aiParamExpr2, Expression.Constant(40))
                ),
                Dynamic2
                )
            );
            Console.WriteLine("AiDynamicDo4:" + laExp.ToString());
            Console.WriteLine("结果:" + laExp.Compile().DynamicInvoke());
            Console.WriteLine();
        }

    //与上例不同的是,本过程不是调用的反射方法
static void AiDynamicDo5(dynamic aiD) { //当调用方法是void类型时 应该用 CSharpBinderFlags.ResultDiscarded //第二个参数是方法名 //第三个参数要泛型时才结出 //第五个参数要与表达示参数据相同 var aiBinder = Binder.InvokeMember(CSharpBinderFlags.None, "add2", null, typeof(Program), new[] { CSharpArgumentInfo.Create(CSharpArgumentInfoFlags.None, null), CSharpArgumentInfo.Create(CSharpArgumentInfoFlags.None, null), CSharpArgumentInfo.Create(CSharpArgumentInfoFlags.None, null) }); ParameterExpression aiParamExpr = Expression.Parameter(typeof(object), "o"); ParameterExpression aiParamExpr1 = Expression.Parameter(typeof(int), "a"); ParameterExpression aiParamExpr2 = Expression.Parameter(typeof(int), "b");         //与上例中不同的地方 DynamicExpression aiDynamic = Expression.MakeDynamic(typeof(Func<CallSite, object, int, int, object>) , aiBinder , aiParamExpr , aiParamExpr1 , aiParamExpr2 ); //下面这种使用方式,在调用时DynamicInvoke(aiD,30,40) //LambdaExpression laExp = Expression.Lambda(Dynamic2, paramExpr, paramExpr1, paramExpr2); LambdaExpression aiLabExp = Expression.Lambda( Expression.Block( new ParameterExpression[] { aiParamExpr, aiParamExpr1, aiParamExpr2 } , Expression.Assign(aiParamExpr, Expression.Constant(aiD)) , Expression.Assign(aiParamExpr1, Expression.Constant(30)) , Expression.Assign(aiParamExpr2, Expression.Constant(40)) , aiDynamic)); Console.WriteLine("AiDynamicDo5:" + aiLabExp.ToString()); Console.WriteLine("结果:" + aiLabExp.Compile().DynamicInvoke()); Console.WriteLine(); }
表达式:使用API创建表达式树(4)DynamicExpression

调用:
            AiDynamicDo2(new AiTestD());

            AiDynamicDo2(new AiTestD2());

            AiDynamicDo3(new AiTestD());

            AiDynamicDo3(new AiTestD2());

            AiDynamicDo4(new AiTestD());

            AiDynamicDo4(new AiTestD2());

            AiDynamicDo5(new AiTestD());

            AiDynamicDo5(new AiTestD2());

输出:
    AiDynamicDo2:() => {var o; ... }
    结果:你好!这是 AiTestD

    AiDynamicDo2:() => {var o; ... }
    结果:你好!这是 AiTestD2

    AiDynamicDo3:(a, b) => Convert System.Object(AiTest(a, b))
    结果:AiTest-动态调用

    AiDynamicDo3:(a, b) => Convert System.Object(AiTest(a, b))
    结果:**AiTest-动态调用

    AiDynamicDo4:() => {var a;var b; ... }
    结果:70

    AiDynamicDo4:() => {var a;var b; ... }
    结果:70000

    AiDynamicDo5:() => {var o;var a;var b; ... }
    结果:-70

    AiDynamicDo5:() => {var o;var a;var b; ... }
    结果:-70000

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表达式:使用API创建表达式树(4)DynamicExpression

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