C# Generics Constraints: Is there a way to express is not a?

Question

I have the following code:

interface IConverter<T, U>
{
    U Convert(T obj);
}

interface IBusinessEntityConveter<T, U> : IConverter<T, U>
    where U : BusinessEntity
{
}

class LookupConveter<B> : IBusinessEntityConveter<Lookup, B>, IConverter<Lookup, Moniker>
    where B : BusinessEntity, new()
{

    #region IConverter<Lookup, Moniker> Members

    public Moniker Convert(Lookup obj)
    {
       //...
    }

    #endregion


    #region IConverter<Lookup,B> Members

    public B Convert(Lookup obj)
    {
       //...
    }

    #endregion
}

I am getting this error:

Error 2 'Convertors.LookupConveter<B>' cannot implement both 'Convertors.IConverter<Microsoft.Crm.Sdk.Lookup,B>' and 'Convertors.IConverter<Microsoft.Crm.Sdk.Lookup,Microsoft.Crm.Sdk.Moniker>' because they may unify for some type parameter substitutions

Is there a way to specify that T isn't a business entity?

Answer 1

No, there are no "negative" constraints.

Answer 2

Nope, I'm afraid not. The only options you have are listed here Constraints on Type Parameters

Answer 3

I have been also trying to use explicit interfaces, as Stefan suggested, but it does not work. I assume IBusinessEntityConveter and IConverter are issuing two different concerns. I think you will have to split it and create two different IBusinessEntityConveters to fullfill both.