System.Reflection.TargetException when an interface is used as class mapping proxy definition

[micmerchant]

Hello,

as u may know, we are currently updating from an old NHibernate 4 (4.0.3) version to the current NHibernate 5 (5.2.3) version and are facing some issues.

We often declare an interface as class proxy, as it is stated in the Mapping Documetation.

proxy (optional): Specifies an interface to use for lazy initializing proxies. You may specify the name of the class itself.

With NHibernate 5 a System.Reflection.TargetException is thrown now, when a Many-To-One reference is updated with a proxy object. I first thought, that this only happens in case of union-subclass-mappings (cause we often used proxy definitions in inheritance mappings), but this isn't the case. It is independ from inheritance mappings. Let me explain.

This is an example model:

public class EntityWithInterfaceProxyDefinition: IEntityProxy
{
	public virtual Guid Id { get; set; }
	public virtual string Name { get; set; }
}

This is the model where it is referenced:

public class EntityWithInterfaceLookup
{
	public virtual Guid Id { get; set; }
	public virtual string Name { get; set; }
	public virtual IEntityProxy EntityLookup { get; set; }
}

I've deactivated the reflection optimization to better debug this problem:

Cfg.Environment.UseReflectionOptimizer = false;

The exception was triggerd from the flush after the update and is thrown here:

protected virtual object GetIdentifierPropertyValue(object entity)
{
	return idGetter.Get(entity);
}

This makes of course sense, because:

entity.GetType().ToString()
"IEntityProxyProxy"
entity.GetType().BaseType.ToString()
"System.Object"
entity.GetType().GetInterfaces()
{System.Type[3]}
    [0]: {Name = "ISerializable" FullName = "System.Runtime.Serialization.ISerializable"}
    [1]: {Name = "INHibernateProxy" FullName = "NHibernate.Proxy.INHibernateProxy"}
    [2]: {Name = "IEntityProxy" FullName = "NHibernate.Test.NHSpecificTest.IlogsProxyTest.IEntityProxy"}
idGetter
{NHibernate.Properties.BasicPropertyAccessor.BasicGetter}
    Method: {System.Guid get_Id()}
    Property: {System.Guid Id}
    PropertyName: "Id"
    ReturnType: {Name = "Guid" FullName = "System.Guid"}
    clazz: {Name = "EntityWithInterfaceProxyDefinition" FullName = "NHibernate.Test.NHSpecificTest.IlogsProxyTest.EntityWithInterfaceProxyDefinition"}
    @property: {System.Guid Id}
    propertyName: "Id"

As you can see, the given entity parameter doesn't inherit from the "EntityWithInterfaceProxyDefinition" class, which is the parent class of the idGetter. So you get an TargetException by invoking the idGetter.

I guess this fix raised this issue:

SHA-1: da56a73

• Fix TransientObjectException in ISession.IsDirty() with many-to-one (Fix #1419 - ISession.IsDirty() shouldn't throw exception for transient many-to-one object in a session #1420)
  Add an explicit check for transient objects in ManyToOne.IsDirty
  Fixes ISession.IsDirty() shouldn't throw exception for transient many-to-one object in a session #1419

I've attached some test mapping classes, as well as a test fixture with two tests to reproduce this problem. The test "UpdateEntityWithInterfaceLookup" fails the other one doesn't fail (cause it uses the clsas itself as proxy)

I know removing the proxy definition should be the workaround for this issue. But as long you don't say, we are doing something completly wrong, i would rather avoid that.

Thx, in adavance.
TargetExceptionTest.zip

[fredericDelaporte]

Regression of 5.0.