Using params keyword with dynamic type arguments

Question

I've declared an interface with Add method to add new item, 2 classes TopicModel and CommentModel to store data.

I've re-write the code in console mode, like this:

interface IAction
{
    void Add<T>(params T[] t) where T : class;
}

class TopicModel
{
    public string Id { get; set; }
    public string Author { get; set; }
}

class CommentModel
{
    public string Id { get; set; }
    public string Content { get; set; }
}

class Topic : IDisposable, IAction
{
    public void Add<T>(params T[] t) where T : class
    {
        var topic = t[0] as TopicModel;
        var comment = t[1] as CommentModel;

        // do stuff...
    }

    public void Dispose()
    {
        throw new NotImplementedException();
    }
}

class MainClass
{
    static void Main()
    {
        var t = new TopicModel { Id = "T101", Author = "Harry" };
        var c = new CommentModel { Id = "C101", Content = "Comment 01" };

        using (var topic = new Topic())
        {
            //topic.Add(t, c);
        }
    }
}

The line topic.Add(t, c) gave me error message:

The type arguments for method 'Topic.Add(params T[])' cannot be inferred from the usage. Try specifying the type arguments explicitly.

Then, I've tried again with:

topic.Add(c, c) // Good :))
topic.Add(t, t, t); // That's okay =))

That's my problem. I want the method accepts 2 different types ( TopicModel and CommentModel ).

And, I don't want to declare:

interface IAction
{
    void Add(TopicModel t, CommentModel c);
}

because another classes can re-use Add method within different argument types.

So, my question is: how to change params T[] t to accept multiple argument types?

Answer 1

TopicModel et CommentModel must inherit same class Or implement same interface. Try This :

interface IAction
{
    void Add<T>(params T[] t) where T : IModel;
}

class IModel
{
}

class TopicModel : IModel
{
    public string Id { get; set; }
    public string Author { get; set; }
}

class CommentModel : IModel
{
    public string Id { get; set; }
    public string Content { get; set; }
}

class Topic : IDisposable, IAction
{
    public void Add<T>(params T[] t) where T : IModel
    {
        var topic = t[0] as TopicModel;
        var comment = t[1] as CommentModel;

        Console.WriteLine("Topic witch ID={0} added",topic.Id);
        Console.WriteLine("Commment witch ID={0} added", comment.Id);
    }

    public void Dispose()
    {

    }
}

class Program
{
    static void Main()
    {
        TopicModel t = new TopicModel { Id = "T101", Author = "Harry" };
        CommentModel c = new CommentModel { Id = "C101", Content = "Comment 01" };

        using (var topic = new Topic())
        {
            topic.Add<IModel>(t, c);
        }

        Console.ReadLine();
    }
}