Introduction
In order to select the first record from a list of entities with LINQ, we use the First or the FirstOrDefault methods.
First
The First method returns the first element of a list , or an InvalidOperationException if the list of elements is empty.
FirstOrDefault
The FirstOrDefault method returns the first element of a list , or a Default value if the list of elements is empty.
-
If the empty list is a list of integer values, then the default value is
0 -
If the empty list is a list of boolean values, then the default value is
false -
If the empty list is a list of nullable values, then the default value is
null
See the Default values table in C#
Examples
Non empty list
List<int> list = new List<int> { 14, 3, 29, 100, 15};
int value1 = list.FirstOrDefault(); // 14
int value2 = list.First(); // 14
Empty list
List<int> list = new List<int> { };
int value1 = list.FirstOrDefault(); // 0
int value2 = list.First(); // InvalidOperationException
List of nullable values
List<string> list = new List<string> { };
string value1 = list.FirstOrDefault(); // null
string value2 = list.First(); // InvalidOperationException
Namespace
To use the First or the FirstOrDefault methods, you have to include this namespace:
using System.Linq;