C# | Check if an element is in the Collection<T>

Collection<T>.Contains(T) method is used to determine whether an element is in the Collection<T>.

Syntax:

public bool Contains (T item);

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

Return Value: This method return True if item is found in the Collection<T>, otherwise, False.

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

Example 1:

// C# code to check if an
// element is in 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>();

        myColl.Add("A");
        myColl.Add("B");
        myColl.Add("C");
        myColl.Add("D");
        myColl.Add("E");

        // Checking if an element is in the Collection
        // The function returns "True" if the
        // item is present in Collection
        // else returns "False"
        Console.WriteLine(myColl.Contains("A"));
    }
}

Output:

True

Example 2:

// C# code to check if an
// element is in 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>();

        myColl.Add(2);
        myColl.Add(3);
        myColl.Add(4);
        myColl.Add(5);

        // Checking if an element is in the Collection
        // The function returns "True" if the
        // item is present in Collection
        // else returns "False"
        Console.WriteLine(myColl.Contains(6));
    }
}

Output:

False

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.contains?view=netframework-4.7.2