反射.Emit:为具有GenericTypeParameterBuilder类型参数的构造类型获取MethodInfo

本文关键字：类型 MethodInfo 获取 类型参数 GenericTypeParameterBuilder Emit 反射 | 更新日期: 2023-09-27 18:16:54

我正在尝试Reflection.Emit一个泛型类，实现用类的泛型参数构造的泛型接口，例如:

class Foo<U>: IEquatable<U>
{
    bool IEquatable<U>.Equals(U other) { /* ... */ }
}

我正在努力为IEquatable<U>.Equals(U)方法获得MethodInfo。

反映构造类型IEquatable<U>抛出NotSupportedException，因为U是GenericTypeParameterBuilder，而TypeBuilder.GetMethod(IEquatable<U>, IEquatable<T>.Equals(T))返回一个奇怪的IEquatable<U>.Equals(T)方法。

感谢任何帮助!

测试代码:

// define class Foo<U>
var tb = moduleBuilder.DefineType("Foo");
var genParams = tb.DefineGenericParameters("U");
// IEquatable<T>.Equals(T) method
var miEqualsT = typeof(IEquatable<>).GetMethod("Equals", typeof(IEquatable<>).GetGenericArguments());
// IEquatable<U> constructed type
var iEquatableU = typeof(IEquatable<>).MakeGenericType(genParams);
// now trying to get IEquatable<U>.Equals(U) method
MethodInfo miEqualsU;
try { miEqualsU = iEquatableU.GetMethod("Equals", genParams); }
catch (NotSupportedException) { Console.WriteLine("Reflecting constructed interface not supported."); }
miEqualsU = TypeBuilder.GetMethod(iEquatableU, miEqualsT);
var declaringType =$"{miEqualsU.DeclaringType.Name}<{miEqualsU.DeclaringType.GenericTypeArguments[0].Name}>";
var parameterType = miEqualsU.GetParameters()[0].ParameterType;
Console.WriteLine($"TypeBuilder.GetMethod() returns {declaringType}.{miEqualsU.Name}({parameterType.Name})");
// OUTPUT:
// Reflecting constructed interface not supported.
// TypeBuilder.GetMethod() returns IEquatable`1<U>.Equals(T)

反射.Emit:为具有GenericTypeParameterBuilder类型参数的构造类型获取MethodInfo

您已经获得了miEqualsT的正确方法。下面是如何使用方法实现接口:

var assemblyName = new AssemblyName { Name = "asd" };
var moduleBuilder = Thread.GetDomain().DefineDynamicAssembly(assemblyName, AssemblyBuilderAccess.Run).DefineDynamicModule(assemblyName.Name);
var tb = moduleBuilder.DefineType("Foo");
var genParams = tb.DefineGenericParameters("U");
var miEqualsT = typeof(IEquatable<>).GetMethod("Equals", typeof(IEquatable<>).GetGenericArguments());
var myMethod = tb.DefineMethod("Equals", MethodAttributes.Public | MethodAttributes.Virtual, typeof(bool), genParams);
var il = myMethod.GetILGenerator();
il.Emit(OpCodes.Ldstr, "I was invoked!");
il.Emit(OpCodes.Call, GetMethod<string>(a => Console.WriteLine(a)));
il.Emit(OpCodes.Ldc_I4_1);
il.Emit(OpCodes.Ret);
tb.AddInterfaceImplementation(typeof(IEquatable<>).MakeGener‌​icType(genParams));
tb.DefineMethodOverride(myMethod, miEqualsT);
var t = tb.CreateType();


//Hack for demonstration
private MethodInfo GetMethod<T>(Expression<Action<T>> thing)
{
    return ((thing as LambdaExpression).Body as MethodCallExpression).Method;
}

然后使用它:

var genericType = t.MakeGenericType(typeof(int));
var tObj = Activator.CreateInstance(genericType);
var method = genericType.GetMethods()
    .Where(m => m.Name == "Equals" && m.DeclaringType == genericType)
    .First();
method.Invoke(tObj, new object[] { 5 });

或:

var tObj = Activator.CreateInstance(genericType);
DoIt(tObj as IEquatable<int>);


private void DoIt(IEquatable<int> obj)
{
    obj.Equals(5);
}
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