Check item exists in list c#

C# Check if Element is present in List

List is a collection of items/elements. You can check if the list contains an item or an object is present in the list.

In this tutorial, we shall learn how to check if an item/element is present in a given List.

To check if an element is present in the list, use List.Contains[] method. The definition of List.Contains[] method is given below.

bool List.Contains[int item]

If given element is present in the list, then List.Contains[] returns True, else, it returns False.

Example 1 Check if Element is in C# List using Contains[]

In the following program, we have a list of integers.

We shall check if element 68 is present in the list or not using Contains[] method. As 68 is present in the list, List.Contains[] method returns True.

Then we shall check if the element 59 is present in the list. As 59 is not present in the list, List.Contains[] method returns false.

Program.cs

using System; using System.Collections.Generic; class Program { static void Main[string[] args] { //create list List nums = new List[]; nums.Add[52]; nums.Add[68]; nums.Add[73]; //check if element is present in the list bool isElementPresent = nums.Contains[68]; Console.WriteLine["68 present in the list : "+isElementPresent]; //check if element is present in the list isElementPresent = nums.Contains[59]; Console.WriteLine["59 present in the list : "+isElementPresent]; } }

Run the above C# program.

Output

68 present in the list : True 59 present in the list : False

Example 2 Check if Object is present in the C# List

In this example, we shall check if a given object is present in the list.

When working with objects, List.Contains[] method considers that two objects are equal only if they refer to same object instance. Two instances with same values for its properties is not considered equal.

Program.cs

using System; using System.Collections.Generic; class Program { static void Main[string[] args] { //create list List cars = new List[]; //add objects to the list cars.Add[new Car["Toyota", 1250000]]; cars.Add[new Car["Tata", 1300000]]; cars.Add[new Car["Honda", 1150000]]; //create a car object Car mycar = new Car["Tata", 1300000]; // check if mycar is present in the list bool isCarPresent = cars.Contains[mycar]; Console.WriteLine[isCarPresent]; } } class Car{ public string name; public int price; public Car[string name, int price]{ this.name = name; this.price = price; } }

Run the C# program.

Output

False

The values for properties are same, but the object instance is not the same.

Let us rewrite the above program and modify as shown below.

Program.cs

using System; using System.Collections.Generic; class Program { static void Main[string[] args] { //create list List cars = new List[]; //add objects to the list Car car1 = new Car["Toyota", 1250000]; cars.Add[car1]; Car car2 = new Car["Tata", 1300000]; cars.Add[car2]; Car car3 = new Car["Honda", 1150000]; cars.Add[car3]; // check if car2 is present in the list bool isCarPresent = cars.Contains[car2]; Console.WriteLine[isCarPresent]; } } class Car{ public string name; public int price; public Car[string name, int price]{ this.name = name; this.price = price; } }

Run the above C# program.

True

In the above program, we have used the same instance, that we added to the list, to check with Contains[] method. So, Contains[] method, when comparing the objects in the list, finds a match for the given object.

Conclusion

In this C# Tutorial, we learned how to check if an element or object is present in the list or not using List.Contains[] method.