CODEWITHSUNDEEP
c#.netgenericsreflection.emit
Yann Olaf
Yann Olaf

Reputation: 597

Emitting non generic type from generic base type

I am trying to create a non generic class from a generic parent. But I allways get InvalidProgramException.

My base classes:

public interface IServiceType{}
public class ServiceType: IServiceType{}
public class EntityType{}
public class KeyType{}

public class Base<TService,TEntity, TKey>
{
    public Base(TService service)
    {
        Service = service;
    }

    public TService Service { get; set; }
}

Type constructor:

static Type CreateType(Type serviceType, Type entityType, Type keyType)
{
    var assemblyName = new AssemblyName("AssName");
    var assemblyBuilder = AppDomain.CurrentDomain.DefineDynamicAssembly(assemblyName, AssemblyBuilderAccess.Run);
    var moduleBuilder = assemblyBuilder.DefineDynamicModule("MainMod");

    var tb = moduleBuilder.DefineType(serviceType.Name.Substring(1)+entityType.Name, TypeAttributes.Public);

    var baseType = typeof (Base<,,>).MakeGenericType(serviceType, entityType, keyType);

    tb.SetParent(baseType);

    var baseCtor = baseType.GetConstructor(new [] {serviceType});
    if (baseCtor == null)
        throw new InvalidOperationException("Base type constuctor not found");

    var constuctor = tb.DefineConstructor(MethodAttributes.Public, CallingConventions.Standard, new[] {serviceType});

    var ilgen = constuctor.GetILGenerator();
    ilgen.Emit(OpCodes.Ldarg_0);
    ilgen.Emit(OpCodes.Call, baseCtor);
    ilgen.Emit(OpCodes.Ret);

  return tb.CreateType();
}

When I am calling invoke I am getting "Exception has been thrown by the target of an invocation."

void Main()
{
    var type = CreateType(typeof(IServiceType), typeof(EntityType), typeof(KeyType));
    var instance = Activator.CreateInstance(type, new ServiceType{});
    instance.Dump();
}

what am I doing wrong?

Upvotes: 1

Views: 85

Answers (1)

leppie
leppie

Reputation: 117330

You need to pass this and the first parameter

var ilgen = constuctor.GetILGenerator();
ilgen.Emit(OpCodes.Ldarg_0); // this
ilgen.Emit(OpCodes.Ldarg_1); // 1st parameter
ilgen.Emit(OpCodes.Call, baseCtor);
ilgen.Emit(OpCodes.Ret);

Protip: Always dump your generated IL to an assembly and check it with PEVerify.

Upvotes: 4

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