Why is this parameter not CLS-compliant?

Question

I am trying to eliminate all the CLS-compliant errors that we have throughout out solution. While I have managed to sort out several (e.g. public variables beginning with an underscore and using unsigned integers), there are a few which I can't seem to find the reason why they are failing.

I have pasted the all the code relevant to one of the problems, there is a fair amount of code, but it only consists of a form constructor, interface and class that implements the interface.

VB.Net form constructor (the warning is on the unitOfWork parameter and reads Type of parameter 'unitOfWork' is not CLS-compliant:

Public Sub New(ByRef unitOfWork As IUnitOfWork)

    MyBase.New()
    InitializeComponent()

    _unitOfWork = unitOfWork

End Sub

The interface IUnitOfWork is as follows:

public interface IUnitOfWork : IDisposable
{
    bool IsInTransaction { get; }

    bool IsDirty { get; }

    object BeginTransaction();

    object BeginTransaction(IsolationLevel isolationLevel);

    void Commit();

    void Rollback();

    object Session { get; }
}

And the one and only implementation of the interface (and therefore the an instance of which will be passed to the form constructor) is this:

public class UnitOfWork : IUnitOfWork
{
    private ISession _session;

    public UnitOfWork(SMSession session)
    {
        if (session == null)
        {
            throw new ArgumentNullException("Session wasn't supplied");
        }

        this._session = (ISession)session.OpenSession();
    }

    public bool IsInTransaction
    {
        get { return this._session.Transaction.IsActive; }
    }

    public bool IsDirty
    {
        get { return this._session.IsDirty(); }
    }

    public object Session
    {
        get { return this._session; }
    }

    public object BeginTransaction() 
    {
        return this._session.BeginTransaction(IsolationLevel.ReadCommitted);
    }

    public object BeginTransaction(IsolationLevel isolationLevel) 
    {
        return this._session.BeginTransaction(isolationLevel);
    }

    public void Commit()
    {
        if (this._session.Transaction == null)
        {
            throw new NullReferenceException
                ("The Transaction has not been initialised");
        }

        this._session.Transaction.Commit();
    }

    public void Rollback()
    {
        if (this._session.Transaction == null)
        {
            throw new NullReferenceException
                ("The Transaction has not been initialised");
        }

        this._session.Transaction.Rollback();
    }

    private bool disposed = false;

    protected virtual void Dispose(bool disposing)
    {
        if (!this.disposed)
        {
            if (disposing)
            {
                this._session.Dispose();
            }
        }
        this.disposed = true;
    }

    public void Dispose()
    {
        if (this._session != null)
        {
            this._session.Dispose();
        }

        Dispose(true);
        GC.SuppressFinalize(this);
    }
}

I am either being blind to the issue (could be the case as I have been staring at this for ages!) or there is another CLS-compliance restriction that I am unaware of. Any suggestions?

Answer 1

My guess is that your C# library itself is not marked with CLSCompliant. I just duplicated the error, with the VB project marked CLSCompliant, and the C# library that it references is not marked CLSCompliant.

I marked the C# library CLSCompliant, and the warning went away.