C＃typedef泛型

Question

I am using a shorthand version for a class, which looks like this:

using NodeSteps = Tuple<Node, int>;

Node is a class defined by myself. This works fine usually, but the problem here is, is that Node is a generic requiring a struct.

My questions are as follows:

1. How are these typedefs called in C#. I know they are not exactly typedefs, but it was the most similar thing I could think of.

2. How can I make a generic version?

using NodeSteps<T> = Tuple<Node<T>, int>;

I noticed this is not the way to do it. I also would like to specify T is a struct.

Answer 1

Use

class NodeSteps<T> : Tuple<Node<T>, int>
{
}

This is the closest equivalent to a typedef I know of. If there are any non-default constructors, you would need to declare them, though.

Answer 2

1. They are called aliases.

2. No, this isn't possible. C# Language spec:

Using aliases can name a closed constructed type, but cannot name an unbound generic type declaration without supplying type arguments.

Therefore, using x<T> = List<T> or something similar isn't possible.

You may use a class (see the other answers(s)) instead.

Answer 3

This is covered in section 9.4.1 of the C# Language spec.

Using aliases can name a closed constructed type, but cannot name an unbound generic type declaration without supplying type arguments.

This is called alias and can not be generic, but right hand of the using can be generic

using ListOfInts = List<int>

is valid

Answer 4

using NodeSteps = Tuple<Node, int>;

is not the equivalent of a typdef but just an alias to that class. It's designed to work around namespace collisions without having to use the whole namespace. What I would do is define a new class:

public class NodeSteps<T> : Tuple<Node<T>, int> where t: struct
{
}

Answer 5

This works:

namespace Test1
{
    class Node<T>
    {
        public T Test()
        {
            return default(T);
        }
    }
}

namespace Test1
{
    using NodeSteps = System.Tuple<Node<string>, int>;

    public class Class1
    {
         public static void Main()
         {
            NodeSteps t1 = new NodeSteps(new Node<string>(), 10);

            t1.Item1.Test();
         }
    }
}