Stack.Contains() Method in C#

This method(comes under System.Collections namespace) is used to check whether a specified element is present is Stack or not. Internally this method checks for equality by calling the Object.Equals method. Also, it performs a linear search, therefore, this method is an O(n) operation, where n is Count.

Syntax:

public virtual bool Contains (object obj);

Here, obj is the object to locate in the Stack. The value can be null.

Return Value: It returns true, if obj is found in the Stack otherwise returns false.

Below programs illustrate the use of above-discussed method:

Example 1:

// C# code to illustrate the
// Stack.Contains() Method
using System;
using System.Collections;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating a Stack
        Stack myStack = new Stack();

        // Inserting the elements into the Stack
        myStack.Push("Geeks");
        myStack.Push("Geeks Classes");
        myStack.Push("Noida");
        myStack.Push("Data Structures");
        myStack.Push("GeeksforGeeks");

        // Checking whether the element is
        // present in the Stack or not
        // The function returns True if the
        // element is present in the Stack,
        // else returns False
        Console.WriteLine(myStack.Contains("GeeksforGeeks"));
    }
}

Output:

True

Example 2:

// C# code to illustrate the
// Stack.Contains() Method
using System;
using System.Collections;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating a Stack
        Stack myStack = new Stack();

        // Inserting the elements
        // into the Stack
        myStack.Push(5);
        myStack.Push(10);
        myStack.Push(15);
        myStack.Push(20);
        myStack.Push(25);

        // Checking whether the element is
        // present in the Stack or not
        // The function returns True if the
        // element is present in the Stack, else
        // returns False
        Console.WriteLine(myStack.Contains(7));
    }
}

Output:

False

Reference:

• https://docs.microsoft.com/en-us/dotnet/api/system.collections.stack.contains?view=netframework-4.7.2