C# | Insert an object at the top of the Stack - Push Operation

Last Updated : 01 Feb, 2019

Stack represents a last-in, first out collection of object. It is used when you need a last-in, first-out access of items. When you add an item in the list, it is called pushing the item and when you remove it, it is called popping the item. Stack<T>.Push(T) Method is used to inserts an object at the top of the Stack<T>. Properties:

The capacity of a Stack<T> is the number of elements the Stack<T> can hold. As elements are added to a Stack<T> , the capacity is automatically increased as required through reallocation.
If Count is less than the capacity of the stack, Push is an O(1) operation. If the capacity needs to be increased to accommodate the new element, Push becomes an O(n) operation, where n is Count. Pop is an O(1) operation.
Stack<T> accepts null as a valid value and allows duplicate elements.

Syntax:

void Push(object obj);

Example:

CSHARP

// C# code to insert an object
// at the top of the Stack
using System;
using System.Collections.Generic;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating a Stack of strings
        Stack<string> myStack = new Stack<string>();

        // Inserting the elements into the Stack
        myStack.Push("one");

        // Displaying the count of elements
        // contained in the Stack
        Console.Write("Total number of elements in the Stack are : ");

        Console.WriteLine(myStack.Count);

        myStack.Push("two");

        // Displaying the count of elements
        // contained in the Stack
        Console.Write("Total number of elements in the Stack are : ");

        Console.WriteLine(myStack.Count);

        myStack.Push("three");

        // Displaying the count of elements
        // contained in the Stack
        Console.Write("Total number of elements in the Stack are : ");

        Console.WriteLine(myStack.Count);

        myStack.Push("four");

        // Displaying the count of elements
        // contained in the Stack
        Console.Write("Total number of elements in the Stack are : ");

        Console.WriteLine(myStack.Count);

        myStack.Push("five");

        // Displaying the count of elements
        // contained in the Stack
        Console.Write("Total number of elements in the Stack are : ");

        Console.WriteLine(myStack.Count);

        myStack.Push("six");

        // Displaying the count of elements
        // contained in the Stack
        Console.Write("Total number of elements in the Stack are : ");

        Console.WriteLine(myStack.Count);
    }
}

Output:

Total number of elements in the Stack are : 1
Total number of elements in the Stack are : 2
Total number of elements in the Stack are : 3
Total number of elements in the Stack are : 4
Total number of elements in the Stack are : 5
Total number of elements in the Stack are : 6

Reference: