How to use DefaultIfEmpty() function in LINQ with C#?

Question

Amrith Chandran · Answer

DefaultIfEmpty() in LINQ (C#)
The DefaultIfEmpty() method in LINQ is used to return a default value when a collection is empty.If the collection has elements, it remains unchanged.If the collection is empty, it returns a collection with a single default value (for example,
0 for numbers, and null for reference types).
and 
Basic Use
using System;
using System.Linq;
using System.Collections.Generic;
class Program
{
   static void Main()
   {
       Listandlt;intandgt; numbers = new Listandlt;intandgt;(); // Empty list
       var result = numbers.DefaultIfEmpty(); // Returns a collection with one element: 0
       Console.WriteLine("Result: " + string.Join(", ", result));
       // Output: Result: 0 (default int value)
   }
}
and 
DefaultIfEmpty() with Linq to SQL
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace MyConsoleApplication
{
   class MindStickSoft
   {
       static void Main()
       {
           Listandlt;intandgt; Numbers = new Listandlt;intandgt; { 3, 5, 7, 2, 8, 4 };
           var filterValue = Numbers.Where(x =andgt; x andgt; 20).DefaultIfEmpty(-1); // now value exist greater than 20;
           Console.WriteLine("Dafult value is: {0}", string.Join(',', filterValue));
           // Output: Dafult value is: -1
       }
   }
}
and 
When to it
When working with queries that may return empty collections but require at least one value.When aggregation functions (sum, average, etc.) are used to avoid exceptions on empty collections.When a fallback/default value is provided instead of manually handling empty collections.
and 
Also, read: 
What are the LINQ Single(), and SingleOrDefault() functions?

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How to use DefaultIfEmpty() function in LINQ with C#?

Ashutosh Kumar Verma

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1 Answers

DefaultIfEmpty() in LINQ (C#)

DefaultIfEmpty() with Linq to SQL

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