Hello,

I'm working in project that I had created composite control to verify
textbox with RequiredFieldVlidator or CompareValidator or
RegularExpressionValidator. The composite control working fine on the regular
web form but when I place composite control in User Control and place User
Control in web form then I got error message: System.NullReferenceException
was unhandled by user code
  Message="Object reference not set to an instance of an object." when I try
to call Composite control in User Control from web form. I do not get any
error if I call some regular asp:TextBox in user control from web form.

Thank you for any advice.

Check if you calling anything from your form in your customer control that
require Load event to fire to initialize.
In general check the order of events they may work differently if you put
your control inside of User Control.
Good luck.
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Hi Madison,

You could configure your VS2005 debugger to break whenever the
NullReferenceException occurs to see which statement is causing the error:

1) Click VS2005 menu Debug/Exceptions
2) Click on button "Find" and input "NullReferenceException", then click OK
3) After it found the exception in the list, click the checkbox at the
right side of it.

In the meanwhile, you could also show some of your code so that we can tell
more clearly what went wrong.


Regards,
Walter Wang (waw***@online.microsoft.com, remove 'online.')
Microsoft Online Community Support

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Hi Madison,

Have you tried above suggestion? Please feel free to let me know if there's
anything I can help.

Regards,
Walter Wang (waw***@online.microsoft.com, remove 'online.')
Microsoft Online Community Support

==================================================
When responding to posts, please "Reply to Group" via your newsreader so
that others may learn and benefit from your issue.
==================================================

This posting is provided "AS IS" with no warranties, and confers no rights.

Hi Walter,
Here is my codes. There is 3 parts
1.  aspx page called user control
2.  asxc user control use composite control and other asp controls
3. composite textbox control
------------------
Measure.aspx
------------------
Protected Sub ResetControls()
        CustomAdmin.SectorCd_ag = Nothing  ---> call user control
        CustomAdmin.CalcRewardAmtInd_ag = Nothing ---> call user control
        CustomAdmin.KWCalcRewardAmt_ag = Nothing ---> call user control
(problem)
        CustomAdmin.KWHCalcRewardAmt_ag = Nothing ---> call user control
(problem)
        CustomAdmin.ThermCalcRewardAmt_ag = Nothing ---> call user control
(problem)
    End Sub

-----------------------
customAdmin.asxc (user control)
-----------------------
---------------------------------
asp:checkbox control property
---------------------------------
Property SectorCd_ag() As String
        Get
            If ckbSector_ag.Checked Then  --->asp:checkbox
                Return "A"
            Else
                Return ""
            End If
        End Get
        Set(ByVal value As String)
            If value = "A" Then
                ckbSector_ag.Checked = True --->asp:checkbox
            Else
                ckbSector_ag.Checked = False --->asp:checkbox
            End If
        End Set
    End Property
------------------------------------
asp:radioButton control property
------------------------------------
Property CalcRewardAmtInd_ag() As String
        Get
            Select Case rdoCalcRewardInd_ag.SelectedIndex
                Case 0
                    Return "Y"
                Case 1
                    Return "N"
                Case Else
                    Return String.Empty
            End Select
        End Get
        Set(ByVal value As String)
            Select Case value
                Case "Y"
                    rdoCalcRewardInd_ag.SelectedIndex = 0
                Case "N"
                    rdoCalcRewardInd_ag.SelectedIndex = 1
                Case Else
                    rdoCalcRewardInd_ag.SelectedIndex = -1
            End Select
        End Set
    End Property
--------------------------------------
composite textbox control property
--------------------------------------
Property KWCalcRewardAmt_ag() As String
        Get
            Return ccKWCalcRewardAmt_ag.Text  ---> composite textbox control
        End Get
        Set(ByVal value As String)  --->called composite textbox control
(problem)
            If (value Is Nothing) Then
                ccKWCalcRewardAmt_ag.Text = Nothing ---> composite textbox
control
            Else
                ccKWCalcRewardAmt_ag.Text = value ---> composite textbox
control
            End If
        End Set
    End Property

---------------
ccTextBox.vb (composite text box control - only part that has problem)
---------------
Public Property Text() As String
            Get
                Return _textbox.Text
            End Get
            Set(ByVal value As String) -- this is problem part
                If (value Is Nothing) Then
                    _textbox.Text = Nothing
                Else
                    _textbox.Text = value
                End If

            End Set
End Property

I got error System.NullReferenceException: Object reference not set to an
instance of an object. Source error point to Property KWCalcRewardAmt_ag in
user control and when I debug the last code is Public Property Text() in
composite control.

Any idea?


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Hi Madison,

Whenever you need to acccess a child control in one of your public
method/property in the composite control class, you need to call
EnsureChildControls() to make sure the child controls are created first.
You can create a private wrapper property to return a child control such as:

Public Class ccTextBox
    Inherits CompositeControl

    Private _textbox As TextBox

    Private ReadOnly Property TheTextBox() As TextBox
        Get
            EnsureChildControls()
            Return _textbox
        End Get
    End Property

    Protected Overrides Sub CreateChildControls()
        Controls.Clear()
        _textbox = New TextBox()
        Controls.Add(_textbox)
    End Sub

    Public Property Text() As String
        Get
            Return TheTextBox.Text
        End Get
        Set(ByVal value As String)
            TheTextBox.Text = value
        End Set
    End Property
End Class


Hope this helps.


Regards,
Walter Wang (waw***@online.microsoft.com, remove 'online.')
Microsoft Online Community Support

==================================================
When responding to posts, please "Reply to Group" via your newsreader so
that others may learn and benefit from your issue.
==================================================

This posting is provided "AS IS" with no warranties, and confers no rights.

Hi Walter,

Thank you for your help. I can refer my composite control from asp page now.

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