有关 System.Reflection.Emit 使用的例子

Question

using System;
using System.Threading;
using System.Reflection;
using System.Reflection.Emit;class TestCtorBuilder {
 
      public static Type DynamicPointTypeGen() {
      
       Type pointType = null;
       Type[] ctorParams = new Type[] {typeof(int),
                        typeof(int),
                        typeof(int)};
     
       AppDomain myDomain = Thread.GetDomain();
       AssemblyName myAsmName = new AssemblyName();
       myAsmName.Name = "MyDynamicAssembly";
    
       AssemblyBuilder myAsmBuilder = myDomain.DefineDynamicAssembly(
                      myAsmName, 
                      AssemblyBuilderAccess.RunAndSave);          ModuleBuilder pointModule = myAsmBuilder.DefineDynamicModule("PointModule",
                                    "Point.dll");       TypeBuilder pointTypeBld = pointModule.DefineType("Point",
                                      TypeAttributes.Public);       FieldBuilder xField = pointTypeBld.DefineField("x", typeof(int),
                                                          FieldAttributes.Public);
       FieldBuilder yField = pointTypeBld.DefineField("y", typeof(int), 
                                                          FieldAttributes.Public);
       FieldBuilder zField = pointTypeBld.DefineField("z", typeof(int),
                                                          FieldAttributes.Public);
           Type objType = Type.GetType("System.Object"); 
           ConstructorInfo objCtor = objType.GetConstructor(new Type[0]);       ConstructorBuilder pointCtor = pointTypeBld.DefineConstructor(
                      MethodAttributes.Public,
                      CallingConventions.Standard,
                      ctorParams);
       ILGenerator ctorIL = pointCtor.GetILGenerator();       // NOTE: ldarg.0 holds the "this" reference - ldarg.1, ldarg.2, and ldarg.3
       // hold the actual passed parameters. ldarg.0 is used by instance methods
       // to hold a reference to the current calling object instance. Static methods
       // do not use arg.0, since they are not instantiated and hence no reference
       // is needed to distinguish them.            ctorIL.Emit(OpCodes.Ldarg_0);       // Here, we wish to create an instance of System.Object by invoking its
         // constructor, as specified above.           ctorIL.Emit(OpCodes.Call, objCtor);       // Now, we'll load the current instance ref in arg 0, along
       // with the value of parameter "x" stored in arg 1, into stfld.           ctorIL.Emit(OpCodes.Ldarg_0);
           ctorIL.Emit(OpCodes.Ldarg_1);
           ctorIL.Emit(OpCodes.Stfld, xField);        // Now, we store arg 2 "y" in the current instance with stfld.           ctorIL.Emit(OpCodes.Ldarg_0);
           ctorIL.Emit(OpCodes.Ldarg_2);
           ctorIL.Emit(OpCodes.Stfld, yField);        // Last of all, arg 3 "z" gets stored in the current instance.           ctorIL.Emit(OpCodes.Ldarg_0);
           ctorIL.Emit(OpCodes.Ldarg_3);
           ctorIL.Emit(OpCodes.Stfld, zField); 
           
           // Our work complete, we return.       ctorIL.Emit(OpCodes.Ret);        // Now, let's create three very simple methods so we can see our fields.       string[] mthdNames = new string[] {"GetX", "GetY", "GetZ"};            foreach (string mthdName in mthdNames) {
              MethodBuilder getFieldMthd = pointTypeBld.DefineMethod(
                           mthdName, 
                           MethodAttributes.Public,
                                           typeof(int), 
                                           null);
          ILGenerator mthdIL = getFieldMthd.GetILGenerator();
       
          mthdIL.Emit(OpCodes.Ldarg_0);
            switch (mthdName) {
             case "GetX": mthdIL.Emit(OpCodes.Ldfld, xField);
                  break;
             case "GetY": mthdIL.Emit(OpCodes.Ldfld, yField);
                  break;
             case "GetZ": mthdIL.Emit(OpCodes.Ldfld, zField);
                  break;          }
          mthdIL.Emit(OpCodes.Ret);           }
       // Finally, we create the type.        pointType = pointTypeBld.CreateType();       // Let's save it, just for posterity.
       
       myAsmBuilder.Save("Point.dll");
    
       return pointType;     }    public static void Main() {
    
       Type myDynamicType = null;
           object aPoint = null;
       Type[] aPtypes = new Type[] {typeof(int), typeof(int), typeof(int)};
           object[] aPargs = new object[] {4, 5, 6};
    
       // Call the  method to build our dynamic class.       myDynamicType = DynamicPointTypeGen();       Console.WriteLine("Some information about my new Type '{0}':",
                  myDynamicType.FullName);
       Console.WriteLine("Assembly: '{0}'", myDynamicType.Assembly);
       Console.WriteLine("Attributes: '{0}'", myDynamicType.Attributes);
       Console.WriteLine("Module: '{0}'", myDynamicType.Module);
       Console.WriteLine("Members: "); 
       foreach (MemberInfo member in myDynamicType.GetMembers()) {
        Console.WriteLine("-- {0} {1};", member.MemberType, member.Name);
       }           Console.WriteLine("---");       // Let's take a look at the constructor we created.       ConstructorInfo myDTctor = myDynamicType.GetConstructor(aPtypes);
           Console.WriteLine("Constructor: {0};", myDTctor.ToString());           Console.WriteLine("---");
      
           // Now, we get to use our dynamically-created class by invoking the constructor.        aPoint = myDTctor.Invoke(aPargs);
           Console.WriteLine("aPoint is type {0}.", aPoint.GetType());
                     // Finally, let's reflect on the instance of our new type - aPoint - and
       // make sure everything proceeded according to plan.       Console.WriteLine("aPoint.x = {0}",
                 myDynamicType.InvokeMember("GetX",
                                BindingFlags.InvokeMethod,
                            null,
                            aPoint,
                            new object[0]));
       Console.WriteLine("aPoint.y = {0}",
                 myDynamicType.InvokeMember("GetY",
                                BindingFlags.InvokeMethod,
                            null,
                            aPoint,
                            new object[0]));
       Console.WriteLine("aPoint.z = {0}",
                 myDynamicType.InvokeMember("GetZ",
                                BindingFlags.InvokeMethod,
                            null,
                            aPoint,
                            new object[0]));               // +++ OUTPUT +++
       // Some information about my new Type 'Point':
       // Assembly: 'MyDynamicAssembly, Version=0.0.0.0'
       // Attributes: 'AutoLayout, AnsiClass, NotPublic, Public'
       // Module: 'PointModule'
       // Members: 
       // -- Field x;
       // -- Field y;
       // -- Field z;
           // -- Method GetHashCode;
           // -- Method Equals;
           // -- Method ToString;
           // -- Method GetType;
           // -- Constructor .ctor;
       // ---
       // Constructor: Void .ctor(Int32, Int32, Int32);
       // ---
       // aPoint is type Point.
       // aPoint.x = 4
       // aPoint.y = 5
       // aPoint.z = 6
        
    }
    
}