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。
class AiTestD
{
public string Name = "你好！这是 AiTestD";
public int Id = ;
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 = ;
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) * ;
}
}
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）
/// <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(); }
调用：
AiDynamicDo(new AiTestD());
AiDynamicDo(new AiTestD2());
输出为：
AiDynamicDo：() => {var o; ... }
结果：123
AiDynamicDo：() => {var o; ... }
结果：789
/// <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()),
Expression.Assign(aiParamExpr2, Expression.Constant())
),
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())
, Expression.Assign(aiParamExpr2, Expression.Constant())
, aiDynamic)); Console.WriteLine("AiDynamicDo5：" + aiLabExp.ToString());
Console.WriteLine("结果：" + aiLabExp.Compile().DynamicInvoke());
Console.WriteLine();
}
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