Posts Tip: Simple Comparer for sorting in VB.NET
Post
Cancel

Tip: Simple Comparer for sorting in VB.NET

Here's a simple routine to sort a collection of objects posted by Jan Tielens.

Dim customers As New ArrayList
'Or you can use the Sort method of the strong typed collection,
'inheriting from CollectionBase.
customers.Sort(New SimpleComparer("Name"))
'or
customers.Sort(New SimpleComparer("Name",  SortOrder.Descending))

The complete code for SimpleComparer class is:

-------- 

Public Class SimpleComparer Implements IComparer

  Private _propertyToSort As String
  Private _sortOrder As SortOrder 

    
  Public Sub New(ByVal propertyToSort As String
    Me.new(propertyToSort, System.Windows.Forms.SortOrder.Ascending)
  End Sub 

  Public Sub New(ByVal propertyToSort As String, ByVal sortOrder As SortOrder)
    MyBase.new()
    _propertyToSort = propertyToSort
    _sortOrder = sortOrder
  End Sub

  Public Function Compare(ByVal x As Object, ByVal y As Object) As Integer _
    Implements System.Collections.IComparer.Compare
    Dim prop As Reflection.PropertyInfo = x.GetType.GetProperty(Me.PropertyToSort)
    If Me.SortOrder = SortOrder.None OrElse prop.GetValue(x, Nothing) = _
      prop.GetValue(y, Nothing) Then
      Return 0
    Else
      If prop.GetValue(x, Nothing) > prop.GetValue(y, Nothing) Then
        If Me.SortOrder = System.Windows.Forms.SortOrder.Ascending Then
          Return 1
        Else
          Return -1
        End If
      Else
        If  Me.SortOrder = System.Windows.Forms.SortOrder.Ascending Then
          Return -1 
        Else
          Return 1
        End If
      End If
    End If
  End Function

  Public Property SortOrder() As SortOrder
    Get
      Return _sortOrder
    End Get
    Set(ByVal Value As SortOrder)
      _sortOrder = Value
    End Set
  End Property 

  Public Property PropertyToSort() As String
    Get
      Return _propertyToSort
    End Get
    Set(ByVal Value As String)
      _propertyToSort = Value
    End Set
  End Property
End Class

This post is licensed under CC BY 4.0 by the author.