具有泛型类型和列表的C＃多态

Question

Maybe my question is simple or just stupid but I have following problem:

I have 2 polymorphic methods:

public void Index<T>(string alias, IEnumerable<T> items) where T : class
{
    var result = Client.IndexMany(items, alias);
    ExceptionHandling(result);
}

public void Index<T>(string alias, T item) where T : class
{
    var result = Client.Index(item, x => x.Index(alias));
    ExceptionHandling(result);
}

When I'm now trying to call the method which is getting a List with following command:

ClientService.Index(Alias, items.ToList());

Always the method Index<T>(string alias, T item) is getting called. How can I change it that Lists call the first Method and single objects call the second Method?

Answer 1

I have an alternative solution!

You can use parameter names to differentiate the overloads!

You see, the first overload's second parameter is called items , whereas the second overload's second parameter is called item . Therefore, if you want to call the first overload, you just need:

ClientService.Index(Alias, items: items.ToList());

If you want the second instead, you can call:

ClientService.Index(Alias, item: items.ToList());

See the difference?

Clean and tidy! Tested on chsarppad: http://csharppad.com/gist/0d7f71c66079fefa680ea3f6afb2ed63

Answer 2

This is the problem with having the same name for a method (overloading) where the two overloads clearly do different things - you have a hint to the solution; elsewhere you have named the downstream methods Index and IndexMany .

Your two options are

1. Name the methods differently, and appropriately
2. Explicitly cast your list to an IEnumerable<T> using AsEnumerable() extension method.

Answer 3

您可以指定通用参数类型，例如

ClientService.Index<Item>(Alias, items.ToList());