c# 使用反射Reflection的Emit实现动态创建元数据及可执行文件

void Main()
{
    string projectName = "HelloWorld";

    AssemblyName assemblyName = new AssemblyName()
    {
       Name = projectName    
    };
    
    //生成一个动态程序集
    AssemblyBuilder assemblyBuilder = AppDomain.CurrentDomain.DefineDynamicAssembly(assemblyName, AssemblyBuilderAccess.Save);
    
    //生成程序集模块
    ModuleBuilder moduleBuilder = assemblyBuilder.DefineDynamicModule(projectName, projectName + ".exe",true);
    
    //设置类
    TypeBuilder typeBuilder = moduleBuilder.DefineType("Program", TypeAttributes.Class);
    //设置方法    
    MethodBuilder mainMethodBuilder = typeBuilder.DefineMethod("Main", MethodAttributes.Public |  MethodAttributes.Static, typeof(void),Type.EmptyTypes);
    
    //指定IL
    ILGenerator ilMain = mainMethodBuilder.GetILGenerator();
    //声明string类型变量
    LocalBuilder msgLocal = ilMain.DeclareLocal(typeof(string));
    //定义变量名
    msgLocal.SetLocalSymInfo("letter");
    ilMain.Emit(OpCodes.Ldstr,"hello world");
    ilMain.Emit(OpCodes.Stloc,msgLocal);
    ilMain.Emit(OpCodes.Ldloc, msgLocal);
    ilMain.EmitCall(OpCodes.Call, Type.GetType("System.Console").GetMethod("WriteLine", new Type[] {typeof(string)}),null);
    ilMain.Emit(OpCodes.Ret);
    
    typeBuilder.CreateType();
    
    assemblyBuilder.SetEntryPoint(mainMethodBuilder);
    assemblyBuilder.Save(projectName + ".exe");
    
    
}

// Define other methods and classes here

另一示例:

// define assembly and module
var propertyName = "Name";
var propertyType = typeof(string);
var ab = AssemblyBuilder.DefineDynamicAssembly(
             new AssemblyName("dynamicAssembly"), 
             AssemblyBuilderAccess.Save);
var mb = ab.DefineDynamicModule("dynamicModule", "dynamicModule.dll");

// define type, field and property
var tb = mb.DefineType("dynamicType");
var fb = tb.DefineField("_name", propertyType, FieldAttributes.Private);
var pb = tb.DefineProperty(propertyName, PropertyAttributes.HasDefault, propertyType, Type.EmptyTypes);
var get = tb.DefineMethod("get_" + propertyName, MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.HideBySig, propertyType, Type.EmptyTypes);
var set = tb.DefineMethod("set_" + propertyName, MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.HideBySig, null, new[] { propertyType });

// write the IL for the get method
var getIl = get.GetILGenerator();
getIl.Emit(OpCodes.Ldarg_0); // this
getIl.Emit(OpCodes.Ldfld, fb); // _name field
getIl.Emit(OpCodes.Ret);

// write the IL for the set method
var setIl = set.GetILGenerator();
Label exitSet = setIl.DefineLabel(); // define label to jump in case condition is false
setIl.Emit(OpCodes.Ldarg_0); // this
setIl.Emit(OpCodes.Ldfld, fb); // _name field
setIl.Emit(OpCodes.Ldarg_1); // value
var inequality = propertyType.GetMethod("op_Inequality", new[] { propertyType, propertyType });
setIl.Emit(OpCodes.Call, inequality); // '!=' method
setIl.Emit(OpCodes.Brfalse_S, exitSet); // check for inequality
setIl.Emit(OpCodes.Ldstr, "changedto:"); // load string literal
setIl.Emit(OpCodes.Ldarg_1); // value
var concat = propertyType.GetMethod("Concat", new[] { propertyType, propertyType });
setIl.Emit(OpCodes.Call, concat); // concat two strings (literal + value)
var writeline = typeof(Console).GetMethod("WriteLine", new[] { propertyType });
setIl.Emit(OpCodes.Call, writeline); // write
setIl.Emit(OpCodes.Ldarg_0); // this
setIl.Emit(OpCodes.Ldarg_1); // value
setIl.Emit(OpCodes.Stfld, fb); // save the new value into _name
setIl.MarkLabel(exitSet); // mark the label
setIl.Emit(OpCodes.Ret); // return
pb.SetGetMethod(get);
pb.SetSetMethod(set);

tb.CreateType(); // complete the type
ab.Save("dynamicModule.dll"); // save the assembly to disk

结果代码

internal class dynamicType
{
    private string _name;

    public string Name
    {
        get
        {
            return this._name;
        }
        set
        {
            if (this._name != value)
            {
                 Console.WriteLine("changedto:" + value);
                 this._name = value;
            }
        }
    }
}