In LINQ (Language-Integrated Query), both the First and FirstOrDefault
methods are used to retrieve the first element from a sequence.
However, there is a difference in how they handle scenarios where no
element matches the specified criteria. Here's a breakdown of the
difference between First and FirstOrDefault
- First method will return the first value, but it is not able to handle null values.
- FirstOrDefault will return the first value, and it is able to handle null values also.
First: The First method returns the first element that matches the specified condition in a sequence. If no matching element is found, it throws an exception (InvalidOperationException).Here's an example using First:
int[] numbers = { 1, 2, 3, 4, 5 };
int firstEvenNumber = numbers.First(n => n % 2 == 0);
Console.WriteLine(firstEvenNumber); // Output: 2
In this example, the First method is used to find the first even number in the numbers array. Since the condition n % 2 == 0 matches the element 2, it is returned as the result. If there were no even numbers in the array, the First method would throw an exception.
FirstOrDefault: The FirstOrDefault method also returns the first element that matches the specified condition in a sequence. However, if no matching element is found, it returns the default value for the type of the elements in the sequence (null for reference types or the default value for value types).Here's an example using FirstOrDefault:
int[] numbers = { 1, 3, 5, 7, 9 };
int firstEvenNumber = numbers.FirstOrDefault(n => n % 2 == 0);
Console.WriteLine(firstEvenNumber); // Output: 0
In this example, since there are no even numbers in the numbers array, the FirstOrDefault method returns the default value for the int type, which is 0. No exception is thrown.
The main difference between First and FirstOrDefault is in their behavior when no matching element is found. First throws an exception, while FirstOrDefault returns the default value. So, if you expect that there might not be a matching element and want to handle that scenario without an exception, you can use FirstOrDefault.