Pushing Items into stack with LINQ

Question

How can i programatically push an array of strings into generic Stack ?

string array

 string[] array=new string[]{"Liza","Ana","Sandra","Diya"};

Stack Setup

 public class stack<T>
 {
    private int index;

    List<T> list; 

    public stack()
    {
        list = new List<T>();
        index=-1;

    }

    public void Push(T obj)
    {

        list.Add(obj);
        index++;
    }
 ...........
}

What is the change do i need here ?

stack<string> slist = new stack<string>();
var v = from vals in array select (p => slist.Push(p));

Error Report :

The type of the expression in the select clause is incorrect.

Answer 1

LINQ is a query language/framework. What you want to perform here is a modification to a collection object rather than a query (selection) - this is certainly not what LINQ is designed for (or even capable of).

What you might like to do, however, is to define an extension method that for the Stack<T> class, however. Note that it also makes sense to here to use the BCL Stack<T> type, which is exactly what you need, instead of reinventing the wheel using List<T>.

public static void PushRange<T>(this Stack<T> source, IEnumerable<T> collection)
{
    foreach (var item in collection)
        source.Push(item);
}

Which would then allow you do the following:

myStack.PushRange(myCollection);

And if you're not already convinced, another philosophical reason: LINQ was created to bring functional paradigms to C#/.NET, and at the core of functional programming is side-effect free code. Combining LINQ with state-modifying code would thus be quite inconsistent.

Answer 2

The first issue is you Push returns a void. Select is expecting a value of something.

You are just doing a loop and don't need to use link.

Since you stack is internally storing a list, you can create a list by passing it an array.

so in your case

List<string> myList = new List<string>(array);

Creats the list.

Answer 3

Push needs a return type for you to be able to use it in a select clause. As it is, it returns void. Your example is, I think, a horrible abuse of LINQ. Even if it worked, you'd be using a side-effect of the function in the select clause to accomplish something totally unrelated to the task that the select is intended for. If there was a "ForEach" extension, then it would be reasonable to use LINQ here, but I'd avoid it and stick with a foreach loop.

 foreach (var val in array)
 {
     slist.Push(val);
 }

This is much clearer in intent and doesn't leave one scratching their head over what you're trying to accomplish.

Answer 4

Change

public void Push(T obj)

to

public T Push(T obj)

and ignore the return values.

Disclaimer: I would not recommend mutation like this.

Answer 5

Try this

string[] arr = new string[]{"a","f"};
var stack = new Stack<string>();
arr.ToList().ForEach(stack.Push);

While this is "cool" is isn't any better than a for loop.