Linq statement with mutiple OrderBy clauses not working

Question

I have a local collection that I am trying to sort with Linq but the returned in memory collection still remains sorted by the numeric ID column FailureID. Any idea why these OrderBy clauses are not taking effect?

Object

Public Class OpenBuildFaultsViewModel

    Public Property FailureID As Int64
    Public Property ModelName As String
    Public Property ZoneName As String
    Public Property Fault As String
    Public Property FaultCode As String
    Public Property FaultCodeDetail As String
    Public Property FaultArea As String
    Public Property MajorAssembly As String
    Public Property SubAssembly As String
    Public Property ComponentAssembly As String
    Public Property BusinessTest As String
    Public Property AuditScore As String
    Public Property Comment As String
    Public Property ShortagePart As String
    Public Property CreatedBy As String
    Public Property FixedByID As Int32
    Public Property FixedByComment As String
    Public Property FixedByFaultRectificationID As Int32

End Class

Order By

Function Index() As ActionResult

        Dim data As IEnumerable(Of OpenBuildFaultsViewModel) = Session("Failures")

        Dim model = From fails In data.Where(Function(w) w.FixedByID.Equals(0)).
                                        OrderBy(Function(o) o.MajorAssembly).
                                        OrderBy(Function(o) o.SubAssembly).
                                        OrderBy(Function(o) o.ComponentAssembly).
                                        OrderBy(Function(o) o.BusinessTest).
                                        OrderBy(Function(o) o.FailureID)

        Return View(model)

    End Function

score 7 · Accepted Answer · answered Aug 15 '12 at 13:31

If you want to order the data by several criteria, you must use OrderBy only for the first criterion. For the next ones, you should use ThenBy:

    Dim model = From fails In data.Where(Function(w) w.FixedByID.Equals(0)).
                                    OrderBy(Function(o) o.MajorAssembly).
                                    ThenBy(Function(o) o.SubAssembly).
                                    ThenBy(Function(o) o.ComponentAssembly).
                                    ThenBy(Function(o) o.BusinessTest).
                                    ThenBy(Function(o) o.FailureID)

If you use OrderBy every time, it "forgets" the previous order and reorders completely by the subsequent criteria, ignoring the previous ones.

BTW, the From fails In part is useless; the following statement has the same meaning:

    Dim model = data.Where(Function(w) w.FixedByID.Equals(0)).
                    OrderBy(Function(o) o.MajorAssembly).
                    ThenBy(Function(o) o.SubAssembly).
                    ThenBy(Function(o) o.ComponentAssembly).
                    ThenBy(Function(o) o.BusinessTest).
                    ThenBy(Function(o) o.FailureID)

Linq statement with mutiple OrderBy clauses not working

1 Answers1