[LINQ Operators] FirstOrDefault

The “FirstOrDefault” operator returns the first element of a sequence, or a default value if no element is found. You can provide the predicate delegate instead of using the “Where” operator.

 

1. Sample Data Object

To test examples, you need to include the <data classes> in your project.

 

2. “FirstOrDefault” operator

  • NonDeferred operator
  • Purpose: Element

 

3. Prototypes

public static T FirstOrDefault<T>(
  this IEnumerable<T> source)

public static T FirstOrDefault<T>(
  this IEnumerable<T> source,
  Func<T, bool> predicate)

The “FirstOrDefault()” operator returns the first element in a sequence just like the “First()” operator. The main difference is that the “FirstOrDefault()” returns a default value if the sequence is empty or there’s no matching element.

 

4. Example 1 (Standard Operator)

IEnumerable<Employee> emps = Employee.GetEmployees();

Employee emp =
  emps.Where(e => e.Name.Contains("Smith")).FirstOrDefault();
Console.WriteLine($"First Matching Employee: {emp.Name}"); // Jane Smith

Employee emp1 =
  emps.Where(e => e.Name.Contains("NoName")).FirstOrDefault();
if(emp1 == null)
{
  Console.WriteLine("Cannot find any employee");
}

 

5. Example 2 (Query Expression)

There’s no corresponding query expression for the “FirstOrDefault()” operator.

 

6. Example 3 (Standard Operator) – with a condition

IEnumerable<Employee> emps = Employee.GetEmployees();

Employee emp =
  emps.FirstOrDefault(e => e.Name.Contains("Smith"));

Console.WriteLine($"First Matching Employee: {emp.Name}"); // Jane Smith

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