How can I delete an item from an array in VB.NET?

Question

How can I delete an item from an array in VB.NET?

Answer 1

Yes, you can delete an element from an array. Here is an extension method that moves the elements as needed, then resizes the array one shorter:

' Remove element at index "index". Result is one element shorter.
' Similar to List.RemoveAt, but for arrays.
 _
Public Sub RemoveAt(Of T)(ByRef a() As T, ByVal index As Integer)
    ' Move elements after "index" down 1 position.
    Array.Copy(a, index + 1, a, index, UBound(a) - index)
    ' Shorten by 1 element.
    ReDim Preserve a(UBound(a) - 1)
End Sub

Usage examples (assuming array starting with index 0):

Dim a() As String = {"Albert", "Betty", "Carlos", "David"}
a.RemoveAt(0)    ' Remove first element => {"Betty", "Carlos", "David"}
a.RemoveAt(1)    ' Remove second element => {"Betty", "David"}
a.RemoveAt(UBound(a))    ' Remove last element => {"Betty"}

Removing First or Last element is common, so here are convenience routines for doing so (I like code that expresses my intent more readably):

 _
Public Sub DropFirstElement(Of T)(ByRef a() As T)
    a.RemoveAt(0)
End Sub

 _
Public Sub DropLastElement(Of T)(ByRef a() As T)
    a.RemoveAt(UBound(a))
End Sub

Usage:

a.DropFirstElement()
a.DropLastElement()

And as Heinzi said, if you find yourself doing this, instead use List(Of T), if possible. List already has "RemoveAt" subroutine, and other routines useful for inserting/deleting elements.