C# 使用TypeBuilder为基类创建传递构造函数
假设我有一个C# 使用TypeBuilder为基类创建传递构造函数,c#,reflection,typebuilder,C#,Reflection,Typebuilder,假设我有一个太空船类,就像这样: public class SpaceShip { public SpaceShip() { } public SpaceShip(IRocketFuelSource fuelSource) { } } 我想在运行时创建一个继承自SpaceShip的类型,并为SpaceShip中的每个类型定义一个构造函数。我不需要构造函数实际执行任何操作,只需要将其参数传递给父级(“传递”构造函数)。例如,如果用C#表示,则生成的类型将如下所示: 让事情有点
太空船
类,就像这样:
public class SpaceShip {
public SpaceShip() { }
public SpaceShip(IRocketFuelSource fuelSource) { }
}
我想在运行时创建一个继承自SpaceShip的类型,并为SpaceShip中的每个类型定义一个构造函数。我不需要构造函数实际执行任何操作,只需要将其参数传递给父级(“传递”构造函数)。例如,如果用C#表示,则生成的类型将如下所示:
让事情有点复杂的是,在运行时之前,我实际上不知道生成的类型将从哪个类继承(因此我必须考虑任意数量的构造函数,可能带有默认参数)
这可能吗?我想如果我有一个大致的方向可以开始的话,我可以找到答案,只是我对TypeBuilder
完全是新手
谢谢 好吧,我在网上找不到任何东西,所以我最终实现了我自己的。这也应该有助于任何人开始编写某种代理
public static class TypeBuilderHelper
{
/// <summary>Creates one constructor for each public constructor in the base class. Each constructor simply
/// forwards its arguments to the base constructor, and matches the base constructor's signature.
/// Supports optional values, and custom attributes on constructors and parameters.
/// Does not support n-ary (variadic) constructors</summary>
public static void CreatePassThroughConstructors(this TypeBuilder builder, Type baseType)
{
foreach (var constructor in baseType.GetConstructors()) {
var parameters = constructor.GetParameters();
if (parameters.Length > 0 && parameters.Last().IsDefined(typeof(ParamArrayAttribute), false)) {
//throw new InvalidOperationException("Variadic constructors are not supported");
continue;
}
var parameterTypes = parameters.Select(p => p.ParameterType).ToArray();
var requiredCustomModifiers = parameters.Select(p => p.GetRequiredCustomModifiers()).ToArray();
var optionalCustomModifiers = parameters.Select(p => p.GetOptionalCustomModifiers()).ToArray();
var ctor = builder.DefineConstructor(MethodAttributes.Public, constructor.CallingConvention, parameterTypes, requiredCustomModifiers, optionalCustomModifiers);
for (var i = 0; i < parameters.Length; ++i) {
var parameter = parameters[i];
var parameterBuilder = ctor.DefineParameter(i + 1, parameter.Attributes, parameter.Name);
if (((int)parameter.Attributes & (int)ParameterAttributes.HasDefault) != 0) {
parameterBuilder.SetConstant(parameter.RawDefaultValue);
}
foreach (var attribute in BuildCustomAttributes(parameter.GetCustomAttributesData())) {
parameterBuilder.SetCustomAttribute(attribute);
}
}
foreach (var attribute in BuildCustomAttributes(constructor.GetCustomAttributesData())) {
ctor.SetCustomAttribute(attribute);
}
var emitter = ctor.GetILGenerator();
emitter.Emit(OpCodes.Nop);
// Load `this` and call base constructor with arguments
emitter.Emit(OpCodes.Ldarg_0);
for (var i = 1; i <= parameters.Length; ++i) {
emitter.Emit(OpCodes.Ldarg, i);
}
emitter.Emit(OpCodes.Call, constructor);
emitter.Emit(OpCodes.Ret);
}
}
private static CustomAttributeBuilder[] BuildCustomAttributes(IEnumerable<CustomAttributeData> customAttributes)
{
return customAttributes.Select(attribute => {
var attributeArgs = attribute.ConstructorArguments.Select(a => a.Value).ToArray();
var namedPropertyInfos = attribute.NamedArguments.Select(a => a.MemberInfo).OfType<PropertyInfo>().ToArray();
var namedPropertyValues = attribute.NamedArguments.Where(a => a.MemberInfo is PropertyInfo).Select(a => a.TypedValue.Value).ToArray();
var namedFieldInfos = attribute.NamedArguments.Select(a => a.MemberInfo).OfType<FieldInfo>().ToArray();
var namedFieldValues = attribute.NamedArguments.Where(a => a.MemberInfo is FieldInfo).Select(a => a.TypedValue.Value).ToArray();
return new CustomAttributeBuilder(attribute.Constructor, attributeArgs, namedPropertyInfos, namedPropertyValues, namedFieldInfos, namedFieldValues);
}).ToArray();
}
}
这正是我要找的!虽然我必须更改为
GetConstructors(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance)
来保护那些讨厌的构造函数。@Dan:太好了,我不确定其他人会需要它。谢谢你添加那个关键词,我必须(错误地)手写声明,然后复制粘贴在正文上。这位先生,是纯金的!
public static class TypeBuilderHelper
{
/// <summary>Creates one constructor for each public constructor in the base class. Each constructor simply
/// forwards its arguments to the base constructor, and matches the base constructor's signature.
/// Supports optional values, and custom attributes on constructors and parameters.
/// Does not support n-ary (variadic) constructors</summary>
public static void CreatePassThroughConstructors(this TypeBuilder builder, Type baseType)
{
foreach (var constructor in baseType.GetConstructors()) {
var parameters = constructor.GetParameters();
if (parameters.Length > 0 && parameters.Last().IsDefined(typeof(ParamArrayAttribute), false)) {
//throw new InvalidOperationException("Variadic constructors are not supported");
continue;
}
var parameterTypes = parameters.Select(p => p.ParameterType).ToArray();
var requiredCustomModifiers = parameters.Select(p => p.GetRequiredCustomModifiers()).ToArray();
var optionalCustomModifiers = parameters.Select(p => p.GetOptionalCustomModifiers()).ToArray();
var ctor = builder.DefineConstructor(MethodAttributes.Public, constructor.CallingConvention, parameterTypes, requiredCustomModifiers, optionalCustomModifiers);
for (var i = 0; i < parameters.Length; ++i) {
var parameter = parameters[i];
var parameterBuilder = ctor.DefineParameter(i + 1, parameter.Attributes, parameter.Name);
if (((int)parameter.Attributes & (int)ParameterAttributes.HasDefault) != 0) {
parameterBuilder.SetConstant(parameter.RawDefaultValue);
}
foreach (var attribute in BuildCustomAttributes(parameter.GetCustomAttributesData())) {
parameterBuilder.SetCustomAttribute(attribute);
}
}
foreach (var attribute in BuildCustomAttributes(constructor.GetCustomAttributesData())) {
ctor.SetCustomAttribute(attribute);
}
var emitter = ctor.GetILGenerator();
emitter.Emit(OpCodes.Nop);
// Load `this` and call base constructor with arguments
emitter.Emit(OpCodes.Ldarg_0);
for (var i = 1; i <= parameters.Length; ++i) {
emitter.Emit(OpCodes.Ldarg, i);
}
emitter.Emit(OpCodes.Call, constructor);
emitter.Emit(OpCodes.Ret);
}
}
private static CustomAttributeBuilder[] BuildCustomAttributes(IEnumerable<CustomAttributeData> customAttributes)
{
return customAttributes.Select(attribute => {
var attributeArgs = attribute.ConstructorArguments.Select(a => a.Value).ToArray();
var namedPropertyInfos = attribute.NamedArguments.Select(a => a.MemberInfo).OfType<PropertyInfo>().ToArray();
var namedPropertyValues = attribute.NamedArguments.Where(a => a.MemberInfo is PropertyInfo).Select(a => a.TypedValue.Value).ToArray();
var namedFieldInfos = attribute.NamedArguments.Select(a => a.MemberInfo).OfType<FieldInfo>().ToArray();
var namedFieldValues = attribute.NamedArguments.Where(a => a.MemberInfo is FieldInfo).Select(a => a.TypedValue.Value).ToArray();
return new CustomAttributeBuilder(attribute.Constructor, attributeArgs, namedPropertyInfos, namedPropertyValues, namedFieldInfos, namedFieldValues);
}).ToArray();
}
}
var typeBuilder = ...; // TypeBuilder for a SpaceShipSubClass
typeBuilder.CreatePassThroughConstructors(typeof(SpaceShip));
var subType = typeBuilder.CreateType(); // Woo-hoo, proxy constructors!