C# | Removing the node at the start of the LinkedList<T>

LinkedList<T>.RemoveFirst method is used to remove the node at the start of the LinkedList<T>.

Syntax:

public void RemoveFirst ();

Exception: The method throws InvalidOperationException if the LinkedList<T> is empty.

Below given are some examples to understand the implementation in a better way:

Example 1:

// C# code to remove the node at
// the start of the LinkedList
using System;
using System.Collections;
using System.Collections.Generic;

class GFG {

    // Driver code
    public static void Main()
    {
        // Creating a LinkedList of Strings
        LinkedList<String> myList = new LinkedList<String>();

        // Adding nodes in LinkedList
        myList.AddLast("A");
        myList.AddLast("B");
        myList.AddLast("C");
        myList.AddLast("D");
        myList.AddLast("E");

        // Displaying the nodes in LinkedList
        Console.WriteLine("The elements in LinkedList are : ");

        foreach(string str in myList)
        {
            Console.WriteLine(str);
        }

        // Removing the node at the start of LinkedList
        myList.RemoveFirst();

        // Displaying the nodes in LinkedList
        Console.WriteLine("The elements in LinkedList are : ");

        foreach(string str in myList)
        {
            Console.WriteLine(str);
        }
    }
}

Output:

The elements in LinkedList are : 
A
B
C
D
E
The elements in LinkedList are : 
B
C
D
E

Example 2:

// C# code to remove the node at
// the start of the LinkedList
using System;
using System.Collections;
using System.Collections.Generic;

class GFG {

    // Driver code
    public static void Main()
    {
        // Creating a LinkedList of Integers
        LinkedList<int> myList = new LinkedList<int>();

        // Removing the node at the start of LinkedList
        // This should raise "InvalidOperationException"
        // as the LinkedList is empty
        myList.RemoveFirst();

        // Displaying the nodes in LinkedList
        Console.WriteLine("The elements in LinkedList are : ");

        foreach(int i in myList)
        {
            Console.WriteLine(i);
        }
    }
}

Runtime Error:

Unhandled Exception:
System.InvalidOperationException: The LinkedList is empty.

Note: This method is an O(1) operation.

Reference:

• https://docs.microsoft.com/en-us/dotnet/api/system.collections.generic.linkedlist-1.removefirst?view=netframework-4.7.2