In C# how can i check if T is of type IInterface and cast to that if my object supports that interface?

Question

In C#, I have a function that passes in T using generics and I want to run a check to see if T is an object that implements a

Answer 1

In my answer, I assume that method FilterMe is used internally and should not be visible outside your model and could be marked private. If my assumption is wrong, you could create a private overload of FilterMe.

In my answer I just removed the generic . I assume that this FilterMe always is about then entities of type T (since it is in the same Model class). This solves the problem about casting between T and TResult. TResult does not have to be marked as IFilterable since none of the members of IFilterable are used. And since the code already checks if T is IFilterable why check again (especially when FilterMe would be private)?

    public IQueryable GetRecords()
    {
        var entities = Repository.Query();
        if (typeof(IFilterable).IsAssignableFrom(typeof(T)))
        {
            //Filterme is a method that takes in IEnumerable
            entities = FilterMe(entities).AsQueryable();
        }
        return entities;
    }

    public IEnumerable FilterMe(IEnumerable linked) 
    {
        var dict = GetDict();
        return linked.Where(r => dict.ContainsKey(r.Id));
    }

If you would create a second FilterMe, replace the IEumerable types with Queryable, so you do not have to convert your entities with AsQueryable().