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When to use .First and when to use .FirstOrDefault with LINQ?

Steilla Mitchel 208 17-Aug-2023

When to use .First and when to use .FirstOrDefault with LINQ?

c# c#  linq 
Updated on 18-Aug-2023
Steilla Mitchel

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Aryan Kumar

Aryan Kumar

18-Aug-2023

The First() and FirstOrDefault() methods in LINQ are both used to return the first element of a sequence. The difference between the two methods is that First() will throw an exception if the sequence is empty, while FirstOrDefault() will return the default value of the sequence's type if the sequence is empty.

Here is an example of how to use the First() method:

C#

var numbers = new List<int>();
numbers.Add(10);
numbers.Add(20);
numbers.Add(30);

var firstNumber = numbers.First();

In this code, the First() method returns the first element of the numbers list, which is 10.

Here is an example of how to use the FirstOrDefault() method:

C#

var numbers = new List<int>();

var firstNumber = numbers.FirstOrDefault();

In this code, the FirstOrDefault() method returns the first element of the numbers list, which is null because the list is empty.

So, when should you use First() and when should you use FirstOrDefault()?

  • Use First() when you are sure that the sequence will not be empty.
  • Use FirstOrDefault() when you are not sure whether the sequence will be empty.

In general, it is better to use FirstOrDefault() because it is more robust. If you use First() and the sequence is empty, your code will throw an exception. This can cause your program to crash.

However, if you use FirstOrDefault() and the sequence is empty, your code will simply return the default value of the sequence's type. This is usually a harmless outcome.

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