Check if an element is in the Collection in C#

To check if an element exists in a Collection in C#, you can use the Contains() method. This method returns true if the specified element is found in the collection, and false otherwise.

The Collection<T> class is part of the System.Collections.ObjectModel namespace and provides a generic collection that can be used as a base class for creating custom collections.

Syntax

Following is the syntax for using the Contains() method −

bool result = collection.Contains(item);

Parameters

• item − The element to search for in the collection.

Return Value

The method returns a bool value:

• true − If the element is found in the collection.

• false − If the element is not found in the collection.

Using Contains() with Integer Collection

Example

using System;
using System.Collections.ObjectModel;

public class Demo {
   public static void Main(){
      Collection<int> col = new Collection<int>();
      col.Add(10);
      col.Add(20);
      col.Add(30);
      col.Add(40);
      col.Add(50);
      col.Add(60);
      col.Add(70);
      col.Add(80);
      Console.WriteLine("Elements in the Collection...");
      foreach(int val in col){
         Console.WriteLine(val);
      }
      Console.WriteLine("Does the collection has the element 70? = "+col.Contains(70));
      Console.WriteLine("Does the collection has the element 100? = "+col.Contains(100));
   }
}

The output of the above code is −

Elements in the Collection...
10
20
30
40
50
60
70
80
Does the collection has the element 70? = True
Does the collection has the element 100? = False

Using Contains() with String Collection

Example

using System;
using System.Collections.ObjectModel;

public class Demo {
   public static void Main(){
      Collection<string> col = new Collection<string>();
      col.Add("John");
      col.Add("Gary");
      col.Add("Tom");
      col.Add("Brad");
      col.Add("Katie");
      col.Add("Andy");
      col.Add("Nathan");
      Console.WriteLine("Elements in the Collection...");
      foreach(string val in col){
         Console.WriteLine(val);
      }
      Console.WriteLine("Does the collection has the value 'Brad'? = "+col.Contains("Brad"));
      Console.WriteLine("Does the collection has the value 'Bradley'? = "+col.Contains("Bradley"));
   }
}

The output of the above code is −

Elements in the Collection...
John
Gary
Tom
Brad
Katie
Andy
Nathan
Does the collection has the value 'Brad'? = True
Does the collection has the value 'Bradley'? = False

How It Works

The Contains()T to compare elements. For reference types like strings, it compares by value. For value types like integers, it performs direct value comparison. The method iterates through the collection until it finds a match or reaches the end.

Conclusion

The Contains() method provides a simple and efficient way to check if an element exists in a Collection<T>. It returns true if the element is found and false otherwise, making it ideal for validation and conditional logic in your applications.