How to implement ​IBindingList​View.Filter like ​dataView.​Filter

I have an implementation of IBindingListView that filters on a single property using the '=' operator that works fair. I am needing to expand it to something like you get with DataView.Filter.

I want to be able to support expressions like x.filter = "LastName = 'Thomas' AND FirstName <> 'John'".

Surely that block of code has been written hundreds of times. Anybody know where I could find it?

This is a partial listing of the existing code:

Public Class BindingListView(Of T) : Inherits BindingList(Of T)   
   Implements IBindingListView
   Dim originalCollection As List(Of T) = New List(Of T)
   Dim SuspendOriginal As Boolean 

   Protected Sub UpdateFilter() Dim equalsPos As Int32 = _filter.IndexOf("=")
      Dim propName As String = _filter.Substring(0, equalsPos).Trim
      Dim criteria As String = _filter.Substring(equalsPos + 1, _filter.Length - equalsPos - 1).Trim
      criteria = criteria.Substring(1, criteria.Length - 2)
      Dim propdesc As PropertyDescriptor = TypeDescriptor.GetProperties(GetType(T))(propName)
      If originalCollection.Count = 0 Then
         originalCollection.AddRange(Me)
      End If
      Me.Clear() 
      Me.SuspendOriginal = True
      For Each item As T In originalCollection
         Dim value As Object = propdesc.GetValue(item)
         If value.ToString = criteria Then
            Me.Add(item)
         End If
      Next
      Me.SuspendOriginal = False
   End Sub
End Class

 

I know the solution lies in parsing the _filter string and putting the three pieces into a collection. 

PropertyName, Criteria and Operator.

But what would be the best way to parse through the _filter string and split it up.  A "Do Loop" using IndexOf to find operators and Join Words "AND" "OR" or maybe just "AND" I think allowing "OR" complicates it quite a bit more.

Filter is trivial with LINQ and expression trees.  For pre-3.5, take a look at Subsonic, nHibernate, or any ORM mapper and see how they implemented filtering.

This is what I have came up with. It is still somewhat limited in scope and a little rough around the edges but works for equality expressions involving multiple properties.

       Private Class Expression
              Friend PropertyName As String
              Friend Criteria As String
              Friend Condition As String
       End Class
 
       Dim SuspendOriginal As Boolean
       Protected Sub UpdateFilter()
              Dim expressions As New List(Of Expression)
              Dim expression As New Expression
              Dim lastPos As Int32 = -1
              Dim startPos As Int32 = 0
              Dim nextVal As String = "P"
              Dim IsString As Boolean
              Dim foundBegining As Boolean
 
              For i As Int32 = 0 To _filter.Length - 1
                     Select Case nextVal
                           Case "P"
                                  If Not foundBegining AndAlso _filter(i) <> " " Then
                                         foundBegining = True
                                         startPos = i
                                  ElseIf foundBegining Then
                                         If _filter(i) = " "c Then
                                                expression.PropertyName = _filter.Substring(startPos, i - startPos)
                                                foundBegining = False
                                                nextVal = "O"
                                         ElseIf _filter(i) = "="c Then
                                                foundBegining = False
                                                expression.PropertyName = _filter.Substring(startPos, i - startPos)
                                                expression.Condition = "="
                                                nextVal = "C"
                                                startPos = i
                                         End If
                                  End If
                           Case "O"
                                  If _filter(i) = "=" Then
                                         expression.Condition = "="
                                         nextVal = "C"
                                         startPos = i
                                  End If
                           Case "C"
                                  If Not foundBegining AndAlso _filter(i) <> " " Then
                                         If _filter(i) = "'" Then IsString = True
                                         foundBegining = True
                                         startPos = i
                                  ElseIf foundBegining Then
                                         If (IsString And _filter(i) = "'") Or (Not IsString And _filter(i) = " ") Or (i = Filter.Length - 1) Then
                                                If IsString Then
                                                       expression.Criteria = _filter.Substring(startPos, i - startPos).Trim("'"c)
                                                Else
                                                       expression.Criteria = _filter.Substring(startPos, i - startPos)
                                                End If
                                                foundBegining = False
                                                expressions.Add(expression)
                                                expression = Nothing
                                                startPos = i
                                                nextVal = "J"
                                         End If
                                  End If
                           Case "J"
                                  If _filter.Substring(i - 2, 3).ToUpper = "AND" Then
                                         expression = New Expression
                                         nextVal = "P"
                                  End If
                     End Select
              Next
 
              If originalCollection.Count = 0 Then
                     originalCollection.AddRange(Me)
              End If
              Me.Clear()
              Me.SuspendOriginal = True
              Dim NoMatch As Boolean
              For Each item As T In originalCollection
                     NoMatch = False
                     For Each entry As Expression In expressions
                           Dim propdesc As PropertyDescriptor = TypeDescriptor.GetProperties(GetType(T))(entry.PropertyName)
                           Dim value As Object = propdesc.GetValue(item)
                           Select Case entry.Condition
                                  Case "="
                                         If value.ToString <> entry.Criteria Then
                                                NoMatch = True
                                                Exit For
                                         End If
                           End Select
                     Next
                     If Not NoMatch Then
                           Me.Add(item)
                     End If
              Next
              Me.SuspendOriginal = False
       End Sub

What about impementing your filters as delegates? The idea is to create a dictionary of filters containing named filters. The filter string then would contain the name of the filter plus the required parameters. Something like this:

Public Class BindingListView(Of T) : Inherits BindingList(Of T)
    Implements IBindingListView

    Delegate Function FilterPredicate(ByVal item As T, ByVal params() As String) As Boolean

    Public FilterDict As Dictionary(Of String, FilterPredicate)

    Dim originalCollection As List(Of T) = New List(Of T)
    Dim SuspendOriginal As Boolean

    Protected Sub UpdateFilter()
        Dim params() As String = _filter.Split(";")
        Dim isMatch As FilterPredicate = FilterDict(params(0)) 'params(0) is name of filter

        If originalCollection.Count = 0 Then
            originalCollection.AddRange(Me)
        End If
        Me.Clear()
        Me.SuspendOriginal = True
        For Each item As T In originalCollection
            If isMatch(item, params) Then
                Me.Add(item)
           End If
        Next
        Me.SuspendOriginal = False
    End Sub

End Class

Then you would define a filter like this:

Function LastNameAndNotFirstName(ByVal c As Customer, ByVal params() As String) As Boolean
    Return c.LastName = params(1) And c.FirstName <> params(2)
End Function

Dim x As BindingListView(Of Customer) = New ...
x.FilterDict.Add("LastNameAndNotFirstName", AddressOf LastNameAndNotFirstName)

Later you can use the filter like this:

x.Filter = "LastNameAndNotFirstName;Thomas;John"

This way you don't need to parse the filter function.

olivier said:

What about impementing your filters as delegates? The idea is to create a dictionary of filters containing named filters. The filter string then would contain the name of the filter plus the required parameters. Something like this:

Public Class BindingListView(Of T) : Inherits BindingList(Of T)
    Implements IBindingListView

    Delegate Function FilterPredicate(ByVal item As T, ByVal params() As String) As Boolean

    Public FilterDict As Dictionary(Of String, FilterPredicate)

    Dim originalCollection As List(Of T) = New List(Of T)
    Dim SuspendOriginal As Boolean

    Protected Sub UpdateFilter()
        Dim params() As String = _filter.Split(";")
        Dim isMatch As FilterPredicate = FilterDict(params(0)) 'params(0) is name of filter

        If originalCollection.Count = 0 Then
            originalCollection.AddRange(Me)
        End If
        Me.Clear()
        Me.SuspendOriginal = True
        For Each item As T In originalCollection
            If isMatch(item, params) Then
                Me.Add(item)
           End If
        Next
        Me.SuspendOriginal = False
    End Sub

End Class

Then you would define a filter like this:

Function LastNameAndNotFirstName(ByVal c As Customer, ByVal params() As String) As Boolean
    Return c.LastName = params(1) And c.FirstName <> params(2)
End Function

Dim x As BindingListView(Of Customer) = New ...
x.FilterDict.Add("LastNameAndNotFirstName", AddressOf LastNameAndNotFirstName)

Later you can use the filter like this:

x.Filter = "LastNameAndNotFirstName;Thomas;John"

This way you don't need to parse the filter function.

ae said:

olivier said:

*snip*

Mister Olivier, any sample complete in  VB.NET ?

Thanks in advanded.

Yes, I have just tried to create a working example of this without success.
So, I too would love to see a working sample to try please Olivier.
Thanks

olivier said:

What about impementing your filters as delegates? The idea is to create a dictionary of filters containing named filters. The filter string then would contain the name of the filter plus the required parameters. Something like this:

Public Class BindingListView(Of T) : Inherits BindingList(Of T)
    Implements IBindingListView

    Delegate Function FilterPredicate(ByVal item As T, ByVal params() As String) As Boolean

    Public FilterDict As Dictionary(Of String, FilterPredicate)

    Dim originalCollection As List(Of T) = New List(Of T)
    Dim SuspendOriginal As Boolean

    Protected Sub UpdateFilter()
        Dim params() As String = _filter.Split(";")
        Dim isMatch As FilterPredicate = FilterDict(params(0)) 'params(0) is name of filter

        If originalCollection.Count = 0 Then
            originalCollection.AddRange(Me)
        End If
        Me.Clear()
        Me.SuspendOriginal = True
        For Each item As T In originalCollection
            If isMatch(item, params) Then
                Me.Add(item)
           End If
        Next
        Me.SuspendOriginal = False
    End Sub

End Class

Then you would define a filter like this:

Function LastNameAndNotFirstName(ByVal c As Customer, ByVal params() As String) As Boolean
    Return c.LastName = params(1) And c.FirstName <> params(2)
End Function

Dim x As BindingListView(Of Customer) = New ...
x.FilterDict.Add("LastNameAndNotFirstName", AddressOf LastNameAndNotFirstName)

Later you can use the filter like this:

x.Filter = "LastNameAndNotFirstName;Thomas;John"

This way you don't need to parse the filter function.

Why not just use dynamic linq and let it parse for you.

Example:
var q = db.Users.Where("UserID>1 and IsValid");

http://weblogs.asp.net/scottgu/archive/2008/01/07/dynamic-linq-part-1-using-the-linq-dynamic-query-library.aspx

staceyw said:

Why not just use dynamic linq and let it parse for you.

Example:
var q = db.Users.Where("UserID>1 and IsValid");

http://weblogs.asp.net/scottgu/archive/2008/01/07/dynamic-linq-part-1-using-the-linq-dynamic-query-library.aspx

ae said:

staceyw said:

*snip*

I  use .NET 3.0 not .NET 3.5, thanks.

 I need full implementation of BindingListView Class for Filter and sample code, please !!!.

Sorry for the dumb question, but why not just download 3.5 and use.  If you use 3.0 already, your almost there.  Just a few more libraries.  Is there a reason you can not use 3.5?

staceyw said:

ae said:

*snip*

Sorry for the dumb question, but why not just download 3.5 and use.  If you use 3.0 already, your almost there.  Just a few more libraries.  Is there a reason you can not use 3.5?

This works although "rough and ready":

Public Class Form1

   Private _BLV As BindingListView(Of Customer)

   Public Sub New()

      ' This call is required by the Windows Form Designer.
      InitializeComponent()

      cboFirstName.SelectedIndex = 0
      cboLastName.SelectedIndex = 0


      _BLV = New BindingListView(Of Customer)

      FillControls()


   End Sub

   Private Sub FillControls()


      _BLV.Add(New Customer("Fred", "Smith"))
      _BLV.Add(New Customer("Fred", "Jones"))
      _BLV.Add(New Customer("Jack", "Jones"))
      _BLV.Add(New Customer("Jack", "Pilchard"))
      _BLV.Add(New Customer("Fred", "Pilchard"))
      _BLV.Add(New Customer("Derek", "Pilchard"))
      _BLV.Add(New Customer("Fred", "Smith"))
      _BLV.Add(New Customer("Derek", "Smith"))
      _BLV.Add(New Customer("Fred", "Smith"))

      dgvCustomers.DataSource = _BLV

      _BLV.FilterDict.Add("LastNameAndNotFirstName", AddressOf _BLV.LastNameAndNotFirstName)
   End Sub

   Private Sub cboFirstName_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cboFirstName.SelectedIndexChanged
      Filter()
   End Sub

   Private Sub cboLastName_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cboLastName.SelectedIndexChanged
      Filter()
   End Sub

   Private Sub Filter()
      If cboFirstName.SelectedIndex <> 0 AndAlso cboLastName.SelectedIndex <> 0 Then
         _BLV.Filter = String.Format("LastNameAndNotFirstName;{0};{1}", cboFirstName.SelectedItem.ToString(), cboLastName.SelectedItem.ToString())
      End If
   End Sub

End Class

Option Strict On
Imports System.ComponentModel

Public Class BindingListView(Of T) : Inherits BindingList(Of T)
   Implements IBindingListView

   Delegate Function FilterPredicate(ByVal item As T, ByVal params() As String) As Boolean

   Public FilterDict As Dictionary(Of String, FilterPredicate) = New Dictionary(Of String, FilterPredicate)

   Dim originalCollection As List(Of T) = New List(Of T)
   Dim SuspendOriginal As Boolean

   Private _Filter As String


   Protected Sub UpdateFilter()
      Dim params() As String = _Filter.Split(CChar(";"))
      Dim isMatch As FilterPredicate = FilterDict(params(0)) 'params(0) is name of filter

      If originalCollection.Count = 0 Then
         originalCollection.AddRange(Me)
      End If
      Me.Clear()
      Me.SuspendOriginal = True
      For Each item As T In originalCollection
         If isMatch(item, params) Then
            Me.Add(item)
         End If
      Next
      Me.SuspendOriginal = False
   End Sub

   Public Function LastNameAndNotFirstName(ByVal c As Customer, ByVal params() As String) As Boolean
      Return c.FirstName = params(1) And c.LastName = params(2)
   End Function


   Public Sub ApplySort(ByVal sorts As System.ComponentModel.ListSortDescriptionCollection) Implements System.ComponentModel.IBindingListView.ApplySort

   End Sub

   Public Property Filter() As String Implements System.ComponentModel.IBindingListView.Filter
      Get
         Return _Filter
      End Get
      Set(ByVal value As String)
         _Filter = value
         UpdateFilter()
      End Set
   End Property

   Public Sub RemoveFilter() Implements System.ComponentModel.IBindingListView.RemoveFilter

   End Sub

   Public ReadOnly Property SortDescriptions() As System.ComponentModel.ListSortDescriptionCollection Implements System.ComponentModel.IBindingListView.SortDescriptions
      Get
         Return Nothing
      End Get
   End Property

   Public ReadOnly Property SupportsAdvancedSorting() As Boolean Implements System.ComponentModel.IBindingListView.SupportsAdvancedSorting
      Get

      End Get
   End Property

   Public ReadOnly Property SupportsFiltering() As Boolean Implements System.ComponentModel.IBindingListView.SupportsFiltering
      Get

      End Get
   End Property
End Class


Public Class Customer
   Private _FirstName As String
   Private _LastName As String

   Public Sub New(ByVal FName As String, ByVal LName As String)
      _FirstName = FName
      _LastName = LName
   End Sub

   Public ReadOnly Property FirstName() As String
      Get
         Return _FirstName
      End Get
   End Property

   Public ReadOnly Property LastName() As String
      Get
         Return _LastName
      End Get
   End Property
End Class