LINQ FirstOrDefault and LastOrDefault operator in VB.NET
This article defines the basic use of FirstOrDefault and LastOrDefault operator in LINQ.
FirstOrDefault operator
The FirstOrDefault operator returns the first element of a sequence, or a default value if no element is found.
Example1
This example defines the FirstOrDefault operator with a integer array without element then it will return 0 value.
Module Module1
Sub Main()
Dim numbers() As Integer = {}
Dim first As Integer = numbers.FirstOrDefault()
MsgBox(first)
End Sub
End Module
OUTPUT
Example2
This example defines the FirstOrDefault operator with a integer array with some element in the array then it will return the first value.
Module Module1
Sub Main()
Dim numbers() As Integer = {1, 2, 3}
Dim first As Integer = numbers.FirstOrDefault()
MsgBox(first)
End Sub
End Module
OUTPUT
Example 3
Module Module1
Sub Main()
Dim numbers As Integer() = {1, 3, 5, 7, 9}
Dim query = numbers.FirstOrDefault(Function(n) n Mod 2 = 0)
MsgBox("The first even element in the sequence:" & query)
End Sub
End Module
OUTPUT
LastOrDefault operator
The LastOrDefault operator returns the last element of a sequence, or a default value if no element is found.
For example
Module Module1
Sub Main()
Dim numbers As Integer() = {1, 3, 5, 7, 9}
Dim query = numbers.FirstOrDefault(Function(n) n Mod 2 = 0)
query = numbers.LastOrDefault(Function(n) n Mod 2 = 1)
MsgBox("The last odd element in the sequence:" & query)
End Sub
End Module
OUTPUT