Question

Here is my code

public interface ITranslator<E, R>
{       
    E ToEntity<T>(R record);
}

class Gens : ITranslator<string, int>
{
    #region ITranslator<string,int> Members

    public string ToEntity<MyOtherClass>(int record)
    {
        return record.ToString();
    }

    #endregion
}

When I compile this, I get an error Type parameter declaration must be an identifier not a type

Why is that I cannot have ToEntity<MyOtherClass> but can only have ToEntity<T> ??

Edit: what is MyOtherClass doing ? I am converting between entities(POCOs equivalent of Entity framework) and record(Object returned by the framework) for multiple tables/classes. So I would want to use this to do my class specific conversion

Answer 1

Your interface has a generic ToEntity<T> method that you’ve made non-generic in your implementation class Gens as ToEntity<MyOtherClass>. (A generic method could take any type parameter, possibly given certain constraints on T. Your Gens class is trying to provide a definition for ToEntity only for the type parameter MyOtherClass, which defeats the purpose of generics.)

In your code example, it’s unclear how your Gens class is trying to use the MyOtherClass type; it’s certainly not involved in the logic of ToEntity. We’d need more information to be able to guide you further.

To illustrate, here’s what your current definition of the ITranslator<E, R> interface offers, in plain English:

“I provide a mechanism to translate
any record of type R into an entity
of type E, this mechanism being
dependent upon any user-specified type
T.”

Your Gens class, on the other hand, the way it’s currently designed, “implements” the above interface like so:

“I can translate integers to strings.
I provide the illusion of allowing
the user to specify a type to control
how this translation is performed, but
in fact there is no choice of type.
The MyOtherClass class is involved
somehow; that’s all I can say.”

From these two descriptions, it’s clear that the Gens class is not really doing what the ITranslator<E, R> interface guarantees. Namely, it is not willing to accept a user-specified type for its ToEntity method. That’s why this code won’t compile for you.