C# Program to Show the Use of Exists Property

The Exists method in C# is a useful method that checks whether any element in a List<T> matches a given condition. This method takes a predicate as an argument and returns a bool value indicating whether any element exists in the list that satisfies the specified condition.

Syntax

Following is the syntax for the Exists method

public bool Exists(Predicate<T> match)

Parameters

• match A Predicate<T> delegate that defines the conditions of the elements to search for.

Return Value

Returns true if at least one element matches the specified predicate; otherwise, false.

Using Exists to Check for Specific Values

Example

using System;
using System.Collections.Generic;

class Program {
   static void Main(string[] args) {
      List<string> fruits = new List<string>() { "apple", "banana", "orange", "grape", "mango" };
   
      bool exists = fruits.Exists(f => f.Equals("apple"));
   
      if (exists) {
         Console.WriteLine("Apple exists in the list");
      } else {
         Console.WriteLine("Apple does not exist in the list");
      }
      
      // Check for non-existing item
      bool existsKiwi = fruits.Exists(f => f.Equals("kiwi"));
      Console.WriteLine("Kiwi exists: " + existsKiwi);
   }
}

The output of the above code is

Apple exists in the list
Kiwi exists: False

Using Exists with Complex Conditions

Example

using System;
using System.Collections.Generic;

class Program {
   static void Main(string[] args) {
      List<int> numbers = new List<int>() { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
   
      // Check if any number is greater than 5
      bool existsGreaterThan5 = numbers.Exists(n => n > 5);
      Console.WriteLine("Number greater than 5 exists: " + existsGreaterThan5);
      
      // Check if any even number exists
      bool existsEven = numbers.Exists(n => n % 2 == 0);
      Console.WriteLine("Even number exists: " + existsEven);
      
      // Check if any number is negative
      bool existsNegative = numbers.Exists(n => n < 0);
      Console.WriteLine("Negative number exists: " + existsNegative);
   }
}

The output of the above code is

Number greater than 5 exists: True
Even number exists: True
Negative number exists: False

Using Exists with Custom Objects

Example

using System;
using System.Collections.Generic;

public class Student {
   public string Name { get; set; }
   public int Age { get; set; }
   public double Grade { get; set; }
   
   public Student(string name, int age, double grade) {
      Name = name;
      Age = age;
      Grade = grade;
   }
}

class Program {
   static void Main(string[] args) {
      List<Student> students = new List<Student>() {
         new Student("Alice", 20, 85.5),
         new Student("Bob", 22, 92.0),
         new Student("Charlie", 19, 78.5)
      };
      
      // Check if any student has grade above 90
      bool existsHighGrade = students.Exists(s => s.Grade > 90);
      Console.WriteLine("Student with grade above 90 exists: " + existsHighGrade);
      
      // Check if any student is under 20
      bool existsYoung = students.Exists(s => s.Age < 20);
      Console.WriteLine("Student under 20 exists: " + existsYoung);
      
      // Check if specific student exists
      bool existsAlice = students.Exists(s => s.Name == "Alice");
      Console.WriteLine("Alice exists: " + existsAlice);
   }
}

The output of the above code is

Student with grade above 90 exists: True
Student under 20 exists: True
Alice exists: True

Comparison with Other Methods

Conclusion

The Exists method provides an efficient way to check if any element in a List<T> satisfies a given condition. It returns true as soon as the first matching element is found, making it more efficient than iterating through the entire collection manually.