LINQ SingleOrDefault Method

In LINQ, SingleOrDefault() method is used to return the single element. In case if there are no elements present in the list/collection, then this will return more than one element and will throw an exception like a Single () method.

Syntax of LINQ SingleOrDefault() Method

Here is the syntax of using the LINQ SingleOrDefault() method to get the single element from the collection.

In the above syntax, we will return the single element from the collection "objList". And if the collection does not contain any element, then it will return the default value.

Example of LINQ SingleOrDefault() Method

Here is the example of the LINQ SingleOrDefault method to get a single element from the collection when an element is not present in the collection.

using System;
using System. Collections;
using System.Collections.Generic;
using System. Linq;
using System. Text;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    class Programme2
    {
        static void Main(string[] args)
        {
//create the object 'objStudnet' of the class 'Student' added the record to the list 
            List<Student> objStudent = new List<Student>()
            {
                new Student() { Name = "Akshay Tyagi", Gender = "Male",Location="Chennai" },
                new Student() { Name = "Vaishali Tyagi", Gender = "Female", Location="Chennai" },
                new Student() { Name = "Arpita Rai", Gender = "Male",Location="Bangalore" },
                new Student() { Name = "Shubham Rastogi", Gender = "Male", Location ="Vizag"},
                new Student() { Name = "Aman Singhal", Gender = "Male", Location="Nagpur"}
            };
    //initialize the array 'vs' from 1 to 5
                int[] vs = { 1, 2, 3, 4, 5 };
    //objStudent.SingleOrDefault() method will return the information of the student
                var user = objStudent.SingleOrDefault(i => i.Name == "Akshay Tyagi");
                string result = user.Name;
                int val = vs.SingleOrDefault(j => j > 5);
                Console.WriteLine("Element from objStudent: {0}", result);
                Console.WriteLine("Element from objList: {0}", val);
                Console.ReadLine();
        }
    }
      class Student
        {
            public string Name { get; set; }
            public string Gender { get; set; }
            public string Location { get; set; }
        }
}

In the above example, we are trying to get the single element from the two lists (objStudent,objList) objects by using the LINQ SingleOrDefault() method

OUTPUT:

The LINQ SingleOrDefault() method will throw the InvalidOperationException error in case if the list/collection returns more than one element.

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    class Programme2
    {
        static void Main(string[] args)
        {
           List<Student> objStudent = new List<Student>()
           {
                new Student() { Name = "Akshay Tyagi", Gender = "Male",Location="Chennai" },
                new Student() { Name = "Vaishali Tyagi", Gender = "Female", Location="Chennai" },
                new Student() { Name = "Arpita Rai", Gender = "Male",Location="Bangalore" },
                new Student() { Name = "Shubham Rastogi", Gender = "Male", Location ="Vizag"},
                new Student() { Name = "Aman Singhal", Gender = "Male", Location="Nagpur"}
            };
    //initialize the objList array from 1 to 5
            int[] objList = { 1, 2, 3, 4, 5 };
    //here SingleOrDefault()method will return the default value
            int val = objList.SingleOrDefault();

            Console.WriteLine("Element from objList: {0}", val);

            Console.ReadLine();

            //int[] vs = { 1, 2, 3, 4, 5 };

            //var user = objStudent.SingleOrDefault(i => i.Name == "Akshay Tyagi");

            //string result = user.Name;

            //int val = vs.SingleOrDefault(j => j > 5);

            //Console.WriteLine("Element from objStudent: {0}", result);

            //Console.WriteLine("Element from objList: {0}", val);

            Console.ReadLine();

        }

    }

    class Student

    {

        public string Name { get; set; }

        public string Gender { get; set; }

        public string Location { get; set; }

    }
}

If we run the above code, it will throw the InvalidOperationException error because "objlist" returns the more than one value.

OUTPUT: