CODEWITHSUNDEEP
c#generics
Morten
Morten

Reputation: 3854

How do I give generics a constraint to reference types?

I have this situation: 

public class FOO<T> where T : IBar
{
    private T _xxx;
    public Y(T xxx)
    {
        if (xxx == null) throw new ArgumentNullException("xxx");
        _xxx = xxx;
    }
}

public interface IBar 
{
    string XString { get; }
}

In the constructor, I am checking T for null. The compiler correctly warns me that I am checking for null on something that may be a value type, as IBar could be implemented by a struct.

How can I constraint T to be a reference type?

Upvotes: 2

Views: 73

Answers (1)

cuongle
cuongle

Reputation: 75326

The typical myth (even I got before) is types which derive from interface are implicitly reference types, but it's actually not. Struct also could have interface.

So, you should add more constraints class to indicate as reference type

public class FOO<T> where T : class, IBar

Upvotes: 5

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