Question

Unable to cast object of type 'System.Collections.Generic.List`1[WindowsApplication1.Car]' to type 'WindowsApplication1.CarCollection'.

Asked by: Hoboly

why there is a error in this line "        cc2 = cc1.FindAll(p1) "?


Unable to cast object of type 'System.Collections.Generic.List`1[WindowsApplication1.Car]' to type 'WindowsApplication1.CarCollection'.

How can I solve it and still want to return CarCollection?

Public Class Form2
 
    Friend Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim cc1 As New CarCollection
        Dim cc2 As CarCollection
        'Dim cc2 As List(Of Car)
        cc1.Add(New Car With {.name = "F1", .price = 10000})
        cc1.Add(New Car With {.name = "F3", .price = 30000})
        cc1.Add(New Car With {.name = "F2", .price = 20000})
        Dim p1 As Predicate(Of Car)
        p1 = AddressOf findCar
        cc2 = cc1.FindAll(p1) '''''''
        DataGridView1.DataSource = cc2
    End Sub
 
    Private Function findCar(ByVal car12 As Car) As Boolean
        If car12.name = "F2" Then
            Return True
        Else
            Return False
        End If
    End Function
 
    Private Sub Form2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
 
    End Sub
End Class
 
 
Friend Class CarCollection
    Inherits List(Of Car)
 
End Class
 
 
Friend Class Car
    Public name As String
    Public price As Integer
End Class

                                  
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Asked On
2009-10-18 at 05:50:19ID24821581
Tags

vb.net

Topics

Microsoft Visual Basic.Net

,

.NET

,

VB Objects

Participating Experts
2
Points
250
Comments
3

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Answers

 

by: Omego2KPosted on 2009-10-18 at 06:05:53ID: 25599715

change your code to this:

Public Class Form2
 
    Friend Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim cc1 As New CarCollection
        Dim cc2 As CarCollection
        'Dim cc2 As List(Of Car)
        cc1.Add(New Car With {.name = "F1", .price = 10000})
        cc1.Add(New Car With {.name = "F3", .price = 30000})
        cc1.Add(New Car With {.name = "F2", .price = 20000})
        Dim p1 As Predicate(Of Car)
        cc2 = cc1.FindAllCars("F2")
        DataGridView1.DataSource = cc2
    End Sub
 
End Class
 
 
Friend Class CarCollection
    Inherits List(Of Car)
 
    Public Function FindAllCars(ByVal name As String) As CarCollection
        Dim foundCol As New CarCollection
 
        For Each car As Car In Me
            If car.name = name Then
                foundCol.Add(car)
            End If
        Next
        Return foundCol
 
    End Function
 
End Class
 
 
Friend Class Car
    Public _name As String
    Public Property Name() As String
        Get
            Return _name
        End Get
        Set(ByVal value As String)
            _name = value
        End Set
    End Property
    Public _price As Integer
    Public Property Price() As Integer
        Get
            Return _price
        End Get
        Set(ByVal value As Integer)
            _price = value
        End Set
    End Property
End Class

                                              
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by: FernandoSotoPosted on 2009-10-18 at 08:52:47ID: 25600250

Hi Hoboly;

To your question, "why there is a error in this line "        cc2 = cc1.FindAll(p1) "?", That is because cc1.FindAll returns a List(Of Car) and not a CarCollection type.

To your question, "How can I solve it and still want to return CarCollection?", The solution to this is simple in the Car class implement Properties this way the List collection can implement IList on your class which is needed by DataGridView.DataSource to get the values to place in the celles.

Friend Class Car
    Private _name As String
    Public Property name() As String
        Get
            Return _name
        End Get
        Set(ByVal value As String)
            _name = value
        End Set
    End Property
    Private _price As Integer
    Public Property price() As Integer
        Get
            Return _price
        End Get
        Set(ByVal value As Integer)
            _price = value
        End Set
    End Property
End Class

Then in your code make these two modifications.

'Dim cc2 As New CarCollection    ' Remove this line
Dim cc2 As List(Of Car)             ' Put this statement back in

Then it should display the results.

Fernando

 

by: HobolyPosted on 2009-11-01 at 20:32:26ID: 31642612

still can't return CarCollection?

20120131-EE-VQP-002

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