NHibernate and virtual methods/properties

NOTE: This post was originally published on July 4, 2008

I love NHibernate but one of the things that bothers the hell out of me is that i keep forgetting to add the virtual keyword to each method or property in my entities. And since NHibernate needs your classes' properties and methods to be virtual, this causes run-time errors when i run my tests. Since i'm already using custom compile time checks, i figured i might as well add another one... from now on, i want my compilation to fail if any of my NHibernate entities have public methods/properties that aren't marked virtual. Once again, it's PostSharp to the rescue:

using System;
using System.Reflection;
 
using PostSharp.Extensibility;
using PostSharp.Laos;
 
namespace Northwind.Aspects
{
    [Serializable]
    [AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Method | AttributeTargets.Property)]
    [MulticastAttributeUsage(MulticastTargets.Method, TargetMemberAttributes = MulticastAttributes.Managed | 
        MulticastAttributes.NonAbstract | MulticastAttributes.Instance | 
        MulticastAttributes.Protected | MulticastAttributes.Public)]
    public class RequireVirtualMethodsAndProperties : OnMethodBoundaryAspect
    {
        public override bool CompileTimeValidate(MethodBase method)
        {
            if (!method.IsVirtual)
            {
                string methodName = method.DeclaringType.FullName + "." + method.Name;
 
                var message = new Message(SeverityType.Fatal, "MustBeVirtual",
                    string.Format("{0} must be virtual", methodName), GetType().Name);
                MessageSource.MessageSink.Write(message);
 
                return false;
            }
 
            return true;
        }
    }
}

And then we make sure this check is applied to my NHibernate entities:

#if DEBUG
[assembly: RequireVirtualMethodsAndProperties(AttributeTargetTypes = "Northwind.Domain.Entities.*")]
#endif

Now, whenever i forget to mark my properties/methods as virtual, i get this:

EXEC : error MustBeVirtual: Northwind.Domain.Entities.Region.RemoveTerritory must be virtual

EXEC : error MustBeVirtual: Northwind.Domain.Entities.Region.AddTerritory must be virtual

EXEC : error MustBeVirtual: Northwind.Domain.Entities.Region.get_Territories must be virtual

EXEC : error MustBeVirtual: Northwind.Domain.Entities.Region.set_Description must be virtual

EXEC : error MustBeVirtual: Northwind.Domain.Entities.Region.get_Description must be virtual

EXEC : error MustBeVirtual: Northwind.Domain.Entities.Region.set_Id must be virtual

EXEC : error MustBeVirtual: Northwind.Domain.Entities.Region.get_Id must be virtual

... Done building project "Northwind.csproj" -- FAILED.

And there we go :)

Posted Sun, 31 August 2008 06:02:00 AM by DavyBrion

Filed under: postsharp, virtual, validation, proxy