NHibernate BasicSample与Nhibernate 3.3

Question

I started a new project and for this project i wanted to use BasicSample (NHibernate best practise, http://www.codeproject.com/Articles/13390/NHibernate-Best-Practices-with-ASP-NET-1-2nd-Ed ) i haven´t used this before and now i get problems. In this project i use NHibernate 3.3.1 and modified the source code from BasicSample to use my entieties. I get this error for every class model (just showing for the class "Month"):

System.TypeInitializationException was unhandled by user code

Message=The type initializer for 'Nested' threw an exception. Source=Project.Data TypeName=Nested StackTrace: at Project.Data.NHibernateSessionManager.get_Instance() in Project.Data\\NHibernateSessionManager.cs:line 28 at Project.Web.NHibernateSessionModule.BeginTransaction(Object sender, EventArgs e) in App_Code\\NHibernateSessionModule.cs:line 27 at System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) InnerException: NHibernate.InvalidProxyTypeException Message=The following types may not be used as proxies: Project.Core.Domain.Calendar.Month: method Equals should be 'public/protected virtual' or 'protected internal virtual' Project.Core.Domain.Calendar.Month: method IsTransient should be 'public/protected virtual' or 'protected internal virtual' Project.Core.Domain.Calendar.Month: method get_Year should be 'public/protected virtual' or 'protected internal virtual' Project.Core.Domain.Calendar.Month: met hod set_Year should be 'public/protected virtual' or 'protected internal virtual' Blockquote

the class looks like:

public class Month : DomainObject<int>
{
    private Year _year;
    public Year Year
    {
        get { return _year; }
        set { _year = value; }
    }

    private string _monthName; 
    public string MonthName
    {
        get { return _monthName; }
        set { _monthName = value; }
    }

    private IList<Consumption> consumptions = new List<Consumption>();
    public IList<Consumption> Consumptions
    {
        get { return new List<Consumption>(consumptions).AsReadOnly(); }
        protected set { consumptions = value; }
    }

    public Month()
    { }

    public override int GetHashCode()
    {
        return (GetType().FullName + "|" +
                MonthName.GetHashCode()).GetHashCode();
    }

Does anoyone know what the problem could be? I have been crosschecking my project and the BasicSample project but i can´t find anything that missmatch.

2.Can someone explain for me how to use the GetHashCode from DaomainObject because i don´t know how to use this one in every class= Should every property in the class be added here?

I hope someone can help me.

Answer 1

The problem is contained in your exception stack trace. You need to read them more carefully:

The following types may not be used as proxies:
Project.Core.Domain.Calendar.Month: method Equals should be 'public/protected virtual' or 'protected internal virtual'
Project.Core.Domain.Calendar.Month: method IsTransient should be 'public/protected virtual' or 'protected internal virtual'
Project.Core.Domain.Calendar.Month: method get_Year should be 'public/protected virtual' or 'protected internal virtual'
Project.Core.Domain.Calendar.Month: method set_Year should be 'public/protected virtual' or 'protected internal virtual'

What it says is basically, that you need to make all public and protected members of your class virtual , otherwise lazy loading won't work.

---

GetHashCode :
The hash code of an instance should not change over the course of its lifetime, therefore you shouldn't include properties that can be changed.

Answer 2

1. NHibernate uses lazy loading by default. It performs it by creating proxy classes from your entities - inheriting from your entity and overriding it's members. In order for this to work, you need to mark all of your entity members as virtual . That was what it complains about in exception message.

2. As for GetHashCode , you should implement it in DomainObject and only use Id in GetHashCode overrides. You should also override Equals . Here you can find reasons why: NHibernate: Reasons for overriding Equals and GetHashCode .