WinForms ComboBox -> DevExpress ComboBoxEdit (migration)

CorySmith — Wed, 29 Jul 2009 10:46:00 GMT

I found a couple of solutions on the DevExpress website for how to use the ComboBoxEdit component the way I wanted, however, none of them seemed to provide a smooth transition from the WinForms databound ComboBox to the DevExpress counterpart. So using some fo the examples that I found, reading through the help and reflecting on the subject for a whole five minutes... here is what I ended up with.

Option Explicit On

Option Strict On

Option Infer On

Imports System.ComponentModel

<ProvideProperty("DisplayMember", GetType(Control))> _

<ProvideProperty("ValueMember", GetType(Control))> _

<ProvideProperty("DataSource", GetType(Control))> _

Public Class ComboBoxEditEx

Inherits DevExpress.XtraEditors.ComboBoxEdit

Private m_valueMember As String

Private m_displayMember As String

<Category("Data")> _

<Description("Indicate the property to display for the items in this control.")> _

Public Property DisplayMember() As String

Get

Return m_displayMember

End Get

Set(ByVal value As String)

m_displayMember = value

End Set

End Property

<Category("Data")> _

<Description("Indicates the property to use as the actual value for the items in the control.")> _

Public Property ValueMember() As String

Get

Return m_valueMember

End Get

Set(ByVal value As String)

m_valueMember = value

End Set

End Property

<Category("Data")> _

<Description("Indicates the list that this control will use to get its items.")> _

Public WriteOnly Property DataSource() As DataTable

Set(ByVal value As DataTable)

Dim item As New ComboItem(Me.ValueMember, Me.DisplayMember)

item.SetDataSource(Me, value)

End Set

End Property

<Browsable(False)> _

Public Property SelectedValue() As Object

Get

Dim item As New ComboItem(ValueMember, DisplayMember)

Return item.GetItemValue(Me)

End Get

Set(ByVal value As Object)

Dim item As New ComboItem(Me.ValueMember, Me.DisplayMember)

item.SelectItem(Me, value)

End Set

End Property

<Browsable(False)> _

Public ReadOnly Property Items() As DevExpress.XtraEditors.Controls.ComboBoxItemCollection

Get

Return Me.Properties.Items

End Get

End Property

End Class

Friend Class ComboItem

Private m_value As Object

Private m_displayText As String

Friend Sub New(ByVal valueMember As Object, ByVal displayMember As String)

m_value = valueMember

m_displayText = displayMember

End Sub

Public Overrides Function ToString() As String

Return m_displayText

End Function

Friend ReadOnly Property Value() As Object

Get

Return m_value

End Get

End Property

Friend Sub SetDataSource(ByRef control As ComboBoxEditEx, ByVal dt As DataTable)

For Each row As DataRow In dt.Rows

Dim item As ComboItem = New ComboItem(row.Item(control.ValueMember), CStr(row.Item(control.DisplayMember)))

control.Properties.Items.Add(item)

End Sub

Friend Function GetItemValue(ByRef control As ComboBoxEditEx) As Object

Dim item As ComboItem = TryCast(control.SelectedItem, ComboItem)

If item Is Nothing Then

Return Nothing

Else

Return item.Value

End If

End Function

Friend Sub SelectItem(ByRef control As ComboBoxEditEx, ByVal value As Object)

Dim index As Integer = 0

For Each obj As Object In control.Properties.Items

Dim item As ComboItem = TryCast(obj, ComboItem)

If item IsNot Nothing AndAlso _

item.Value.Equals(value) Then

Exit For

Else

index += 1

End If

If index >= control.Properties.Items.Count Then

control.SelectedIndex = -1

Else

control.SelectedIndex = index

End If

End Sub

End Class

The overall goal was to provide a seemless transition (read: drop in replacement) for the comboboxes I already had on existing forms to migrate to use all devexpress controls since I wanted to take advantage of the skinning tech in XtraForm. So what I needed was an easy way to take the existing datatables I had bound to WinForms ComboBox's, the code already used to assign (SelectedValue and SelectedIndex depending on circumstances). So far this has worked out pretty nicely. If you are in the same situation... here you go...

AddressOf.com : DevExpress

WinForms ComboBox -> DevExpress ComboBoxEdit (migration)