I have a list (i.e. Dim nList as new List(of className)). Each class has a property named zIndex (i.e. className.zIndex). Is it possible to sort the elements of the list by the zIndex variable in all of the elements of the list?
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3 Answers
Assuming you have LINQ at your disposal:
Sub Main()
Dim list = New List(Of Person)()
'Pretend the list has stuff in it
Dim sorted = list.OrderBy(Function(x) x.zIndex)
End Sub
Public Class Person
Public Property zIndex As Integer
End Class
Or if LINQ isn't your thing:
Dim list = New List(Of Person)()
list.Sort(Function(x, y) x.zIndex.CompareTo(y.zIndex))
'Will sort list in place
LINQ offers more flexibility; such as being able to use ThenBy if you want to order by more than one thing. It also makes for a slightly cleaner syntax.
5 Comments
Freesnöw
I was unable to use the LINQ example, how would I enable that? I got the second one to work though, thanks :)
vcsjones
@DalexL It depends on the framework version you are targeting. You need 3.5 or greater. The VB.NET Compiler should import the System.Linq namespace for you. (Look on the References tab of the Project's properties).
Jay Imerman
OK, I am comparing dates. When I use my line
a.Sort(Function(x, y) x.DelegationDate.CompareTo(y.DelegationDate)), it doesn't sort at all. It leaves it in the original order.vcsjones
@JayImerman I think you should start a new question with more information about the classes and dates you are trying to sort, and more could around your example.
DrMarbuse
My list was defined as
Dim list = new List(Of Person) and I had to use list = list.OrderBy(Function(x) x.zIndex).ToList to get the sorted list.You can use a custom comparison to sort the list:
nList.Sort(Function(x, y) x.zIndex.CompareTo(y.zIndex))
If not LINQ, then you can implement the IComparable(Of ClassName) to your class:
Public Class ClassName
Implements IComparable(Of ClassName)
'Your Class Stuff...
Public Function CompareTo(ByVal other As ClassName) As Integer Implements System.IComparable(Of ClassName).CompareTo
If _ZIndex = other.ZIndex Then
Return 0
Else
If _ZIndex < other.ZIndex Then
Return -1
Else
Return 1
End If
End If
End Function
End Sub
and then from your code:
nList.Sort()
1 Comment
vcsjones
You can shorten that entire
CompareTo method to Return _ZIndex.CompareTo(other.ZIndex)