C# | Removing first occurrence of object from Collection<T>

Collection<T>.Remove(T) is used to remove the first occurrence of a specific object from the Collection<T>.

Syntax:

public bool Remove (T item);

Here, item is the object to remove from the Collection<T>. The value can be null for reference types.

Return Value: True if item is successfully removed, otherwise, False. This method also returns False if item was not found in the original Collection<T>.

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

Example 1:

// C# code to remove the first
// occurrence of a specific object
// from the Collection
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;

class GFG {

    // Driver code
    public static void Main()
    {
        // Creating a collection of strings
        Collection<string> myColl = new Collection<string>();

        // Adding elements in Collection myColl
        myColl.Add("A");
        myColl.Add("B");
        myColl.Add("C");
        myColl.Add("D");
        myColl.Add("E");

        // Displaying the number of elements in myColl
        Console.WriteLine("Count : " + myColl.Count);

        // Displaying the elements in myColl
        foreach(string str in myColl)
        {
            Console.WriteLine(str);
        }

        // Removing the first occurrence of
        // a specific object from the Collection
        myColl.Remove("C");

        // Displaying the number of elements in myColl
        Console.WriteLine("Count : " + myColl.Count);

        // Displaying the elements in myColl
        foreach(string str in myColl)
        {
            Console.WriteLine(str);
        }
    }
}

Output:

Count : 5
A
B
C
D
E
Count : 4
A
B
D
E

Example 2:

// C# code to remove the first
// occurrence of a specific object
// from the Collection
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;

class GFG {

    // Driver code
    public static void Main()
    {
        // Creating a collection of ints
        Collection<int> myColl = new Collection<int>();

        // Adding elements in Collection myColl
        myColl.Add(2);
        myColl.Add(3);
        myColl.Add(4);
        myColl.Add(4);
        myColl.Add(5);

        // Displaying the number of elements in myColl
        Console.WriteLine("Count : " + myColl.Count);

        // Displaying the elements in myColl
        foreach(int i in myColl)
        {
            Console.WriteLine(i);
        }

        // Removing the first occurrence of
        // a specific object from the Collection
        myColl.Remove(4);

        // Displaying the number of elements in myColl
        Console.WriteLine("Count : " + myColl.Count);

        // Displaying the elements in myColl
        foreach(int i in myColl)
        {
            Console.WriteLine(i);
        }
    }
}

Output:

Count : 5
2
3
4
4
5
Count : 4
2
3
4
5

Note: This method performs a linear search. Therefore this method is an O(n) operation, where n is Count.

Reference:

• https://docs.microsoft.com/en-us/dotnet/api/system.collections.objectmodel.collection-1.remove?view=netframework-4.7.2