Datagridview Not Showing derived class properties?

Question

Hallo,

I have a following code and i am trying to get all the properties from the derived class to showup on the datagridview through bindingsource. Any idea why it is not showing up? thanks

Imports System.ComponentModel

Public Class Form1
    Public BS As New BindingSource
    Public equipments As New BindingList(Of Equipment)
    
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        equipments.Add(New Motor With {.Name = "M1", .HorsePower = 10})
        equipments.Add(New Motor With {.Name = "M2", .HorsePower = 20})
        equipments.Add(New Motor With {.Name = "M3", .HorsePower = 30})
        equipments.Add(New Engine With {.Name = "E1", .FuelType = "Diesel"})
        equipments.Add(New Engine With {.Name = "E2", .FuelType = "Petrol"})
        BS.DataSource = equipments
        DataGridView1.DataSource = BS
    End Sub

End Class

Public Class Equipment
    Public Property Name As String
    Public Property Group As String
End Class

' Implement on Motor class
Public Class Motor
    Inherits Equipment
    Implements IEquipment

    Public Property HorsePower As Integer

    Public Function GetSpecifications() As Dictionary(Of String, Object) Implements IEquipment.GetSpecifications
        Dim specs As New Dictionary(Of String, Object) From {
                                                            {"Horse Power", HorsePower}
                                                                                     }
        Return specs
    End Function
End Class

Public Class Engine
    Inherits Equipment
    Implements IEquipment

    Public Property FuelType As String
    Public Function GetSpecifications() As Dictionary(Of String, Object) Implements IEquipment.GetSpecifications
        Dim specs As New Dictionary(Of String, Object) From {
                                                            {"Fuel Type", FuelType}
                                                                                     }
        Return specs
    End Function

End Class

Interface IEquipment
    Function GetSpecifications() As Dictionary(Of String, Object)
End Interface

Also i am trying to dynamically databind derived class properties to textboxes on button click.

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

        ' Get selected equipment
        'Dim selectedEquipment = CType(selectedRow.DataBoundItem, Equipment)

        Dim selectedEquipment = CType(BS.Current, Equipment)

        ' Get its type  
        Dim equipmentType = selectedEquipment.GetType()

        ' Create instance of that type
        Dim equipment As IEquipment = CType(Activator.CreateInstance(equipmentType), Equipment)

        ' Copy values from selected to new instance
        Dim specs = equipment.GetSpecifications()


        Dim NewX As Integer = 10
        Dim NewY As Integer = 10


        For Each prop In equipmentType.GetProperties()
            prop.SetValue(equipment, prop.GetValue(selectedEquipment))
            Debug.Print(prop.Name & ": " & prop.GetValue(selectedEquipment))

            Dim ValtxtBox As New TextBox
            Dim Speclbl As New Label
            Dim Unitlbl As New Label

            Speclbl.Text = prop.Name
            Speclbl.Location = New Point(NewX, NewY)
            Me.Controls.Add(Speclbl)

            'txtBox.DataBindings.Add("Text", BS, prop.Name)
            ValtxtBox.Location = New Point(NewX + 100, NewY - 3)
            Me.Controls.Add(ValtxtBox)

            NewY += 28

        Next

 End Sub

Answer 1

Hi @Hobbyist_programmer ,

You can use reflection to dynamically determine the properties of the derived classes and add them as columns in the DataGridView.

    Private Sub GetProperties()

        ' Clear existing columns

        DataGridView1.Columns.Clear()

        ' Keep track of added columns to avoid duplicates

        Dim addedColumns As New HashSet(Of String)

        ' Add columns for properties of the base class

        For Each prop As PropertyInfo In GetType(Equipment).GetProperties()

            If Not addedColumns.Contains(prop.Name) Then

                DataGridView1.Columns.Add(prop.Name, prop.Name)

                DataGridView1.Columns(prop.Name).DataPropertyName = prop.Name

                addedColumns.Add(prop.Name)

            End If

        Next

        ' Iterate through the items in the list to determine additional columns based on the derived class type

        For Each item As Equipment In equipments

            Dim itemType = item.GetType()

            Dim properties = itemType.GetProperties()

            For Each prop As PropertyInfo In properties

                ' Exclude properties from the base class

                If prop.DeclaringType IsNot GetType(Equipment) Then

                    If Not addedColumns.Contains(prop.Name) Then

                        DataGridView1.Columns.Add(prop.Name, prop.Name)

                        DataGridView1.Columns(prop.Name).DataPropertyName = prop.Name

                        addedColumns.Add(prop.Name)

                    End If

                    ' Populate cell with corresponding data

                    Dim rowIndex As Integer = equipments.IndexOf(item)

                    Dim columnIndex As Integer = DataGridView1.Columns(prop.Name).Index

                    Dim value As Object = prop.GetValue(item)

                    DataGridView1.Rows(rowIndex).Cells(columnIndex).Value = value

                End If

            Next

        Next

    End Sub

Best Regards.

Jiachen Li

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