Here is a DateTimePicker that supports DBNull... have fun!

For those of you who are interested by a datetime picker that accepts Null
values. Here is a simple extension of the Microsoft DateTimePicker control.
I did not fully tested and code can be optimized. But it's a good start-up.

Notes:
* Use the NullableValue property to bind your data to the control.
* NullableValue will return DBNull if the checked property is true as
opposed to the Value property (inherited from DateTimePicker) that stills
returned a date.
* Since DateTimePicker doesn't allow an inherited class to change the
displayed text, I used custom formats to hide the date from the user...

FYI: I built it based on a thread "How to make DateTimePicker display
nothing?" found in the
microsoft.public.dotnet.framework.windowsforms.controls newsgroup.

For those of you who are interested in more, you may take a look at this
link: http://www.smithvoice.com/dropcal.htm. I didn't have time to check it
but, it could be interesting.

'-----------------------------------------------------------
'Filename : DateTimePickerEx.vb
'Description: Contains all the classes needed to handle the extended
datetime picker.
'History :
'-----------------------------------------------------------
Imports System.ComponentModel

'-----------------------------------------------------------
'Class name : DateTimePickerEx
'Description: Extends the datetimepicker class to allow binding a
DBNull database value
' to it.
'
' This class uses the display format to simulate an
"empty" selection since the
' base datetimepicker class doesn't support displaying an
empty text string.
'
' Since DBNull is not compatible with Date datatype, I
created a new method called
' NullableValue to support it.
'History :
'-----------------------------------------------------------
Public Class DateTimePickerEx
Inherits System.Windows.Forms.DateTimePicker

Private m_enmOriginalFormat As Windows.Forms.DateTimePickerFormat
Private m_strOriginalCustomFormat As String
Private m_blnRefreshing As Boolean = False

#Region " Windows Form Designer generated code "

Public Sub New()
MyBase.New()

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

'Add any initialization after the InitializeComponent() call
initializemembers()
End Sub

'UserControl overrides dispose to clean up the component list.
Protected Overloads Overrides Sub Dispose(ByVal disposing As
Boolean)
If disposing Then
If Not (components Is Nothing) Then
components.Dispose()
End If
End If
MyBase.Dispose(disposing)
End Sub

'Required by the Windows Form Designer
Private components As System.ComponentModel.IContainer

'NOTE: The following procedure is required by the Windows Form
Designer
'It can be modified using the Windows Form Designer.
'Do not modify it using the code editor.
<System.Diagnostics.DebuggerStepThrough()> Private Sub
InitializeComponent()
components = New System.ComponentModel.Container()
End Sub

#End Region

#Region " Event Declarations "

Public Event NullableValueChanged As EventHandler

'-----------------------------------------------------------
'Description: Raise the NullableValueChanged event.
' Required for "Bindable" properties.
'Return :
'Parameters :
'History :
'-----------------------------------------------------------
Protected Overridable Sub OnNullableValueChanged(ByVal e As
EventArgs)
RaiseEvent NullableValueChanged(Me, e)
End Sub

#End Region

#Region " Public Methods and Properties "

'-----------------------------------------------------------
'Description: Gets or Sets the date time picker value.
' Accepts DBNull values.
'Return :
'Parameters :
'History :
'-----------------------------------------------------------
<Bindable(True), _

DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)> _
Public Property NullableValue() As Object
Get
If Me.Checked Then
Return (DBNull.Value)
Else
Return (Me.Value)
End If
End Get
Set(ByVal newValue As Object)

Dim blnRaiseEvent As Boolean = False

If newValue Is DBNull.Value Then
'If the value changed
If Me.Checked Then

Me.Checked = False
Me.RefreshText()
blnRaiseEvent = True
End If

ElseIf IsDate(newValue) Then

'If only the "Checked" state changes (newValue parameter
is equal to the Value property)
'We must raise the NullableValueChanged event manually
since the parents ValueChanged
'event won't be fired.
blnRaiseEvent = (Not Me.Checked) And (CType(newValue,
Date).Equals(Me.Value))

Me.Checked = True
Me.Value = CType(Value, Date)
Me.RefreshText()

Else
Throw New ArgumentException()
End If

If blnRaiseEvent Then
Me.OnNullableValueChanged(New EventArgs())
End If

End Set
End Property

#End Region

#Region " Base Class Overrides "

'-----------------------------------------------------------
'Description: When the user changes the value, we need to refresh
' the display text formats and to throw our
NullableValueChanged event.
'Return :
'Parameters :
'History :
'-----------------------------------------------------------
Protected Overrides Sub OnValueChanged(ByVal e As System.EventArgs)

Me.RefreshText()

'When the value changes, the nullable value also changes.
Me.OnNullableValueChanged(e)

MyBase.OnValueChanged(e)
End Sub

'-----------------------------------------------------------
'Description: If the format is changed we need to get the
' new format and store it as the new original format.
'Return :
'Parameters :
'History :
'-----------------------------------------------------------
Protected Overrides Sub OnFormatChanged(ByVal e As System.EventArgs)

'If the format changes because of our RefreshText method, we
don't want to save
'the "temporary" format used to hide text as our original
format...

If Not m_blnRefreshing Then
Me.SaveOriginalFormats()
End If

MyBase.OnFormatChanged(e)
End Sub

'-----------------------------------------------------------
'Description: When the control is ask to refresh itself, we also
' refresh the display format.
'Return :
'Parameters :
'History :
'-----------------------------------------------------------
Public Overrides Sub Refresh()
Me.RefreshText()

MyBase.Refresh()
End Sub

#End Region

'-----------------------------------------------------------
'Description: Initialize the member variables.
'Return :
'Parameters :
'History :
'-----------------------------------------------------------
Private Sub InitializeMembers()
Me.SaveOriginalFormats()

'The default for the DateTimePickerEx is to display the
checkbox.
MyBase.ShowCheckBox = True
End Sub

'-----------------------------------------------------------
'Description: Save the current display formats.
'Return :
'Parameters :
'History :
'-----------------------------------------------------------
Private Sub SaveOriginalFormats()
m_enmOriginalFormat = Me.Format
m_strOriginalCustomFormat = Me.CustomFormat
End Sub

'-----------------------------------------------------------
'Description: Restore the original display formats
'Return :
'Parameters :
'History :
'-----------------------------------------------------------
Private Sub RestoreOriginalFormats()
Me.CustomFormat = m_strOriginalCustomFormat
Me.Format = m_enmOriginalFormat
End Sub

'-----------------------------------------------------------
'Description: Refresh the display format based on the current
state
' (Checked or not)
'Return :
'Parameters :
'History :
'-----------------------------------------------------------
Private Sub RefreshText()

m_blnRefreshing = True

If Me.Checked Then
Me.RestoreOriginalFormats()
Else
Me.Format = Windows.Forms.DateTimePickerFormat.Custom
Me.CustomFormat = " "
End If

m_blnRefreshing = False

End Sub

End Class

Oups there was a bug... ;)

Correction follows...

Pascal.

Public Sub New()
MyBase.New()

#End Region

#Region " Event Declarations "

#End Region

If Not Me.Checked Then

ElseIf IsDate(newValue) Then

Me.Checked = True
Me.Value = CType(newValue, Date)
Me.RefreshText()

End Set
End Property

#End Region

#Region " Base Class Overrides "

Me.RefreshText()

MyBase.OnValueChanged(e)
End Sub

MyBase.OnFormatChanged(e)
End Sub

MyBase.Refresh()
End Sub

#End Region

m_blnRefreshing = True

m_blnRefreshing = False

End Sub

End Class

"Pascal G." <nospam***pgill***@***vrsi.ca***> wrote in message
news:u8YlBcX...@TK2MSFTNGP10.phx.gbl...

Hi,

do you found the bug ?

regards,
Andreas Epp

"Pascal G." <nospam***pgill***@***vrsi.ca***> schrieb im Newsbeitrag
news:##Lu1euGD...@tk2msftngp13.phx.gbl...

[...]

Hi NG,

does anybody know where the bug is ?

regards,
Andreas Epp