在.net中的代码中创建类类型# [英] Create a class type in code in .net c#
问题描述
当我寻找System.Linq.Expression功能(在代码中创建表达式树,编译它们,执行它们)时,我问自己,如果这是可能的类创建,特别是泛型类。
我会期望像Expression.Class()或Expression.GenericClass()。看看方法我没有看到任何这些。这将是非常实用的,因为我可以动态构建业务对象 - 即时。其实这是我需要的。
有一个例子说明如何使用.net c#在All-In-One Framework codeplex项目中执行此操作
http://1code.codeplex.com/
//定义程序集和模块。
AppDomain appDomain = AppDomain.CurrentDomain;
AssemblyName assemblyName = new AssemblyName(EmittedAssembly);
AssemblyBuilder assembly = appDomain.DefineDynamicAssembly(
assemblyName,AssemblyBuilderAccess.RunAndSave);
//程序集由可执行模块组成。对于单模块
//程序集,模块名称和文件名与
//程序集名称相同。
ModuleBuilder module = assembly.DefineDynamicModule(
assemblyName.Name,assemblyName.Name +.dll);
//////////////////////////////////////// ///////////////////////////////
//声明类型(类)。
//
//声明类ClassA
TypeBuilder classA = module.DefineType(ClassA,TypeAttributes.Public);
//声明类ClassB
TypeBuilder classB = module.DefineType(ClassB,TypeAttributes.Public);
//定义字段stringField,classBField
FieldBuilder stringField = classA.DefineField(stringField,
typeof(string),FieldAttributes.Private);
FieldBuilder classBField = classA.DefineField(classBField,
classB,FieldAttributes.Public);
////////////////////////////////////////// ///////////////////////////
//定义属性ClassBProperty
PropertyBuilder classBProperty = classA.DefineProperty(
ClassBProperty,PropertyAttributes.None,classB,null);
//属性集& get方法的特殊属性集
MethodAttributes getSetAttr = MethodAttributes.Public |
MethodAttributes.SpecialName | MethodAttributes.HideBySig;
//为ClassBProperty定义get访问器方法
MethodBuilder classBGetProp = classA.DefineMethod(
get_ClassBProperty,getSetAttr,classB,Type.EmptyTypes);
ILGenerator classBGetIL = classBGetProp.GetILGenerator();
classBGetIL.Emit(OpCodes.Ldarg_0);
classBGetIL.Emit(OpCodes.Ldfld,classBField);
classBGetIL.Emit(OpCodes.Ret);
//为ClassBProperty定义访问器方法
MethodBuilder classBSetProp = classA.DefineMethod(
set_ClassBProperty,getSetAttr,null,new Type [] {classB}) ;
ILGenerator sampleSetIL = classBSetProp.GetILGenerator();
sampleSetIL.Emit(OpCodes.Ldarg_0);
sampleSetIL.Emit(OpCodes.Ldarg_1);
sampleSetIL.Emit(OpCodes.Stfld,classBField);
sampleSetIL.Emit(OpCodes.Ret);
//将get& set方法映射到PropertyBuilder
classBProperty.SetGetMethod(classBGetProp);
classBProperty.SetSetMethod(classBSetProp);
////////////////////////////////////////// ///////////////////////////
//定义一个使用classBField的方法
MethodBuilder classAMethod = classA.DefineMethod (ClassAMethod,
MethodAttributes.Public);
//定义列表泛型和ienumerable泛型
类型listOf = typeof(List<>);
Type enumOf = typeof(IEnumerable<>);
类型listOfClassA = listOf.MakeGenericType(classA);
类型enumOfClassA = enumOf.MakeGenericType(classA);
//为ClassB定义方法ClassBMethod
MethodBuilder classBMethod = classB.DefineMethod(ClassBMethod,
MethodAttributes.Public,typeof(void),new Type [] {listOfClassA});
classBMethod.DefineParameter(1,ParameterAttributes.None,list);
//写入调用ClassBMethod的ClassAMethod的主体
ILGenerator ilgenA = classAMethod.GetILGenerator();
ilgenA.Emit(OpCodes.Nop);
ilgenA.Emit(OpCodes.Ldarg_0);
ilgenA.Emit(OpCodes.Ldfld,classBField);
ilgenA.Emit(OpCodes.Ldnull);
ilgenA.Emit(OpCodes.Callvirt,classBMethod);
ilgenA.Emit(OpCodes.Ret);
////////////////////////////////////////// ///////////////////////////
//创建类型。
//
classA.CreateType();
classB.CreateType();
////////////////////////////////////////// ///////////////////////////
//保存程序集。
//
assembly.Save(assemblyName.Name +.dll);对不起,这有点长..:-P When I was looking to the System.Linq.Expression capabilities (creating expression trees in code, compiling them, executing them) I was asking myself if this is possible for class creation as well - specifically generic classes.
I would expect something like Expression.Class() or Expression.GenericClass(). Looking at the methods I did not see any of those. It would be very practical, since I could build business objects dynamically - on the fly. Actually that is what I need. If there is another approach to that in .net c# that is also of interest to me.
解决方案 There is an example of how to do this in All-In-One Framework codeplex project
http://1code.codeplex.com/
// Define the assembly and the module.
AppDomain appDomain = AppDomain.CurrentDomain;
AssemblyName assemblyName = new AssemblyName("EmittedAssembly");
AssemblyBuilder assembly = appDomain.DefineDynamicAssembly(
assemblyName, AssemblyBuilderAccess.RunAndSave);
// An assembly is made up of executable modules. For a single-module
// assembly, the module name and file name are the same as the
// assembly name.
ModuleBuilder module = assembly.DefineDynamicModule(
assemblyName.Name, assemblyName.Name + ".dll");
/////////////////////////////////////////////////////////////////////
// Declare the types (classes).
//
// Declare the class "ClassA"
TypeBuilder classA = module.DefineType("ClassA", TypeAttributes.Public);
// Declare the class "ClassB"
TypeBuilder classB = module.DefineType("ClassB", TypeAttributes.Public);
// Define the fields stringField, classBField
FieldBuilder stringField = classA.DefineField("stringField",
typeof(string), FieldAttributes.Private);
FieldBuilder classBField = classA.DefineField("classBField",
classB, FieldAttributes.Public);
/////////////////////////////////////////////////////////////////////
// Define the property ClassBProperty
PropertyBuilder classBProperty = classA.DefineProperty(
"ClassBProperty", PropertyAttributes.None, classB, null);
// The special set of attributes for the property set&get methods
MethodAttributes getSetAttr = MethodAttributes.Public |
MethodAttributes.SpecialName | MethodAttributes.HideBySig;
// Define the "get" accessor method for ClassBProperty
MethodBuilder classBGetProp = classA.DefineMethod(
"get_ClassBProperty", getSetAttr, classB, Type.EmptyTypes);
ILGenerator classBGetIL = classBGetProp.GetILGenerator();
classBGetIL.Emit(OpCodes.Ldarg_0);
classBGetIL.Emit(OpCodes.Ldfld, classBField);
classBGetIL.Emit(OpCodes.Ret);
// Define the "set" accessor method for ClassBProperty
MethodBuilder classBSetProp = classA.DefineMethod(
"set_ClassBProperty", getSetAttr, null, new Type[] { classB });
ILGenerator sampleSetIL = classBSetProp.GetILGenerator();
sampleSetIL.Emit(OpCodes.Ldarg_0);
sampleSetIL.Emit(OpCodes.Ldarg_1);
sampleSetIL.Emit(OpCodes.Stfld, classBField);
sampleSetIL.Emit(OpCodes.Ret);
// Map the get&set methods to PropertyBuilder
classBProperty.SetGetMethod(classBGetProp);
classBProperty.SetSetMethod(classBSetProp);
/////////////////////////////////////////////////////////////////////
// Define a method that uses the classBField
MethodBuilder classAMethod = classA.DefineMethod("ClassAMethod",
MethodAttributes.Public);
// Define the list generics and ienumerable generic
Type listOf = typeof(List<>);
Type enumOf = typeof(IEnumerable<>);
Type listOfClassA = listOf.MakeGenericType(classA);
Type enumOfClassA = enumOf.MakeGenericType(classA);
// Define the method, ClassBMethod, for ClassB
MethodBuilder classBMethod = classB.DefineMethod("ClassBMethod",
MethodAttributes.Public, typeof(void), new Type[] { listOfClassA });
classBMethod.DefineParameter(1, ParameterAttributes.None, "list");
// Write the body of ClassAMethod that calls ClassBMethod
ILGenerator ilgenA = classAMethod.GetILGenerator();
ilgenA.Emit(OpCodes.Nop);
ilgenA.Emit(OpCodes.Ldarg_0);
ilgenA.Emit(OpCodes.Ldfld, classBField);
ilgenA.Emit(OpCodes.Ldnull);
ilgenA.Emit(OpCodes.Callvirt, classBMethod);
ilgenA.Emit(OpCodes.Ret);
/////////////////////////////////////////////////////////////////////
// Create the types.
//
classA.CreateType();
classB.CreateType();
/////////////////////////////////////////////////////////////////////
// Save the assembly.
//
assembly.Save(assemblyName.Name + ".dll");
Sorry this is a bit long.. :-P
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