I have a following generic class:
public class SearchResult<T>
{
public int ResultCount { get; set; }
public IEnumerable<T> Result { get; set; }
}
I also have a Bird
class, which implements IFlyble
interface:
public class Bird : IFlyable
{
public void Fly() {}
}
public interface IFlyable
{
void Fly();
}
I also have a variable res
of type object
.
How do I check if res
is a SearchResult<IFlyable>
?
I tryied this way:
if (res.GetType().IsAssignableFrom(typeof(SearchResult<IFlyable>)))
{
///
}
And this way:
if(res is SearchResult<IFlyable>)
{
///
}
But it does not seems to work.
The problem you are having is probably due to the fact that SearchResult<Bird>
is not convertible to SearchResult<IFlyable>
because SearchResult<T>
is invariant in T
.
C# only admits generic type variance in interfaces and delegates. You need to define an ISearchResult<>
interface that is covariant in its generic type.
In your case, if it’s acceptable that T
is only used as an output you could define such interface as follows:
public interface ISearchResult<out T>
{
int ResultCount { get; }
IEnumerable<T> Result { get; }
}
And now a ISearchResult<Bird>
is a ISearchResult<IFlyable>
because you’ve given the compiler enough information so that it can verify that the conversion is in fact safe.