Sorting generic list(of obj) with mulltiple keys: VB net

Sorting generic list(of obj) with mulltiple keys

I need to sort a generic list with multiple keys ... for example, I want to sort a list of person objects by Age within Department.

I can sort the list to Age OK but when I then re-sort this sorted list by Department the Age sequence is destroyed.

Is there a way to preserve the sub-order?

Public Class Form1
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim lst As New List(Of cls)
        For age = 1 To 12 'generate test data
            lst.Add(New cls(age))
        Next
        For i = 0 To 11
            lst(i).dept = Math.Truncate(i / 4)
        Next
        cls.sortType = sortTypes.Dept
        lst.Sort()
        For i = 0 To 11
            Debug.Print(lst(i).dept & " : " & lst(i).age)
        Next
    End Sub
End Class
Public Enum sortTypes
    age
    dept
End Enum
Friend Class cls
    Implements IComparable(Of cls)
    Public Shared sortType As sortTypes
    Friend dept As Integer = 0
    Friend age As Integer = 0
    Public Sub New(ByVal _i)
        age = _i
    End Sub
    Public Function SortKey() As Object
        If sortType = sortTypes.age Then Return age
        Return dept
    End Function
    Public Overloads Function compareTo(ByVal other As cls) As Integer Implements IComparable(Of cls).CompareTo
        If SortKey() = other.SortKey Then Return 0
        Return IIf(other.SortKey > SortKey(), -1, 1)
    End Function
 
End Class

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Dim sortedLst As List(Of cls) = (From c In lst _ Order By c.dept, c.age _ Select c).ToList()

If you don't want LINQ, then you compare on the first field and store that value. If they are equal (zero is returned) then you compare on the second field, and so on...

Public Class Form1 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim lst As New List(Of cls)
        For age = 1 To 12 'generate test data
            lst.Add(New cls(age))
        Next
        For i = 0 To 11
            lst(i).dept = Math.Truncate(i / 4)
        Next
        cls.SortType = cls.sortTypes.DeptAge
        lst.Sort()
        For i = 0 To 11
            Debug.Print(lst(i).dept & " : " & lst(i).age)
        Next
    End Sub 
End Class 
Friend Class cls
    Implements IComparable(Of cls) 
    Public Enum sortTypes
        Age
        Dept
        AgeDept
        DeptAge
    End Enum 
    Public Shared SortType As sortTypes 
    Friend dept As Integer = 0
    Friend age As Integer = 0 
    Public Sub New(ByVal _i)
        age = _i
    End Sub 
    Public Overloads Function compareTo(ByVal other As cls) As Integer Implements IComparable(Of cls).CompareTo
        Select Case cls.SortType
            Case sortTypes.Age
                Return Me.age.CompareTo(other.age) 
            Case sortTypes.Dept
                Return Me.dept.CompareTo(other.dept) 
            Case sortTypes.AgeDept
                Dim ret As Integer = Me.age.CompareTo(other.age)
                If ret = 0 Then
                    ret = Me.dept.CompareTo(other.dept)
                End If
                Return ret 
            Case sortTypes.DeptAge
                Dim ret As Integer = Me.dept.CompareTo(other.dept)
                If ret = 0 Then
                    ret = Me.age.CompareTo(other.age)
                End If
                Return ret 
        End Select
    End Function 
End Class

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Sorting generic list(of obj) with mulltiple keys

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VB net

.NET Framework 3.x versions

VB Controls

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