How to check whether a List contains a specified element in C#

To check whether a List contains a specified element in C#, you use the Contains() method. This method returns true if the element is found in the list, and false otherwise.

Syntax

Following is the syntax for the Contains() method −

bool Contains(T item)

Parameters

item: The element to search for in the list. The type T represents the element type of the list.

Return Value

Returns a bool value − true if the item is found, false if not found.

Using Contains() with String List

Example

using System;
using System.Collections.Generic;

public class Demo {
   public static void Main(String[] args) {
      List<string> countries = new List<string>();
      countries.Add("India");
      countries.Add("US");
      countries.Add("UK");
      countries.Add("Canada");
      countries.Add("Poland");
      countries.Add("Netherlands");
      
      Console.WriteLine("Countries in the list:");
      foreach (string country in countries) {
         Console.WriteLine(country);
      }
      
      Console.WriteLine("\nChecking if specific countries exist:");
      Console.WriteLine("Does list contain 'Canada'? " + countries.Contains("Canada"));
      Console.WriteLine("Does list contain 'Germany'? " + countries.Contains("Germany"));
   }
}

The output of the above code is −

Countries in the list:
India
US
UK
Canada
Poland
Netherlands

Checking if specific countries exist:
Does list contain 'Canada'? True
Does list contain 'Germany'? False

Using Contains() with Integer List

Example

using System;
using System.Collections.Generic;

public class Demo {
   public static void Main(String[] args) {
      List<int> numbers = new List<int>();
      numbers.Add(100);
      numbers.Add(200);
      numbers.Add(300);
      numbers.Add(400);
      numbers.Add(500);
      
      Console.WriteLine("Numbers in the list:");
      foreach (int num in numbers) {
         Console.WriteLine(num);
      }
      
      Console.WriteLine("\nChecking if specific numbers exist:");
      Console.WriteLine("Does list contain 300? " + numbers.Contains(300));
      Console.WriteLine("Does list contain 150? " + numbers.Contains(150));
   }
}

The output of the above code is −

Numbers in the list:
100
200
300
400
500

Checking if specific numbers exist:
Does list contain 300? True
Does list contain 150? False

Using Contains() with Custom Objects

When using Contains() with custom objects, the method uses the default equality comparer, which compares object references for reference types.

Example

using System;
using System.Collections.Generic;

class Person {
   public string Name { get; set; }
   public int Age { get; set; }
   
   public Person(string name, int age) {
      Name = name;
      Age = age;
   }
   
   public override bool Equals(object obj) {
      if (obj is Person other)
         return Name == other.Name && Age == other.Age;
      return false;
   }
   
   public override int GetHashCode() {
      return Name.GetHashCode() ^ Age.GetHashCode();
   }
}

public class Demo {
   public static void Main(String[] args) {
      List<Person> people = new List<Person>();
      Person person1 = new Person("Alice", 25);
      Person person2 = new Person("Bob", 30);
      
      people.Add(person1);
      people.Add(person2);
      
      Person searchPerson = new Person("Alice", 25);
      
      Console.WriteLine("Does list contain Alice (25)? " + people.Contains(searchPerson));
      Console.WriteLine("Does list contain Charlie (35)? " + people.Contains(new Person("Charlie", 35)));
   }
}

The output of the above code is −

Does list contain Alice (25)? True
Does list contain Charlie (35)? False

Conclusion

The Contains() method provides an efficient way to check if a List contains a specific element. It returns true if found and false otherwise. For custom objects, you may need to override the Equals() method to define custom equality logic.