asked on

Difficult! Bound user control property haschanges in dataset when no changes are made.

When databinding to the text property of a textbox the getchanges property of the dataset will only return values if the textbox is changed.
If I bind to a property of any usercontrol, dataset.haschanges will always be true.
I want my property to work like the text property.
Any code replies can be in C#.NET or VB.NET.

Here is the relevent code:

'User Control Property Declaration:
_________________________________________________________
Public Class UserControl1
Inherits System.Windows.Forms.UserControl
Private _BindMe As String

<Bindable(True)> _
Public Property BindMe() As String
Get
Dim myBinding As Windows.Forms.Binding
Return _BindMe
End Get
Set(ByVal Value As String)
_BindMe = Value
End Set
End Property

End Class
__________________________________________________________
'FORM Code

'DataBinding:
Me.UserControl11.DataBindings.Add(New System.Windows.Forms.Binding("BindMe", Me.DataSet11, "Customers.CompanyName"))

'Save:
Me.BindingContext.Item(Me.DataSet11, "Customers").EndCurrentEdit()
MsgBox("Has Changes: " & Me.DataSet11.HasChanges.ToString)
Me.SqlDataAdapter1.Update(Me.DataSet11)

jackiechen858

http://www.freeweb.hu/noiseehc/SimpleBind.html

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jackiechen858

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RobertRFreeman

ASKER

Thank you both very much. Here is the code in VB. Now I can make properties that handle simple binding correctly. WooHoo!
I found more documentation under Property Usage Guidelines in MSDN by searching for "property-changed events" or "properties, usage guidelines" in the index.

Public Event BindMeChanged As PropertyChangedEventHandler

<Bindable(True)> _
Public Property BindMe() As String
Get
Dim myBinding As Windows.Forms.Binding
Return _BindMe
End Get
Set(ByVal Value As String)
If _BindMe <> Value Then
_BindMe = Value
RaiseEvent BindMeChanged(Me, New PropertyChangedEventArgs("BindMe"))
End If
End Set
End Property

jackiechen858

you are welcome.

RobertRFreeman

ASKER

My last post has a bug, here is the correct code.

Private _BindMe As String
Public Event BindMeChanged As EventHandler

<Bindable(True)> _
Public Property BindMe() As String
Get
Dim myBinding As Windows.Forms.Binding
Return _BindMe
End Get
Set(ByVal Value As String)
If _BindMe <> Value Then
_BindMe = Value
RaiseBindMeChanged()
End If
End Set
End Property

Protected Sub RaiseBindMeChanged()
RaiseEvent BindMeChanged(Me, New EventArgs)
End Sub

jackiechen858

When I read your code, I really thought there is a PropertyChangedEventHandler :-)

RobertRFreeman

ASKER

There is. :) It just doesn't work like I thought. Let me know if you figure out what it does.

RobertRFreeman

ASKER

One other issue I found with using a usercontrol as a combobox is that the text is highlighted on initialization. I think I found a workaround, but this solution causes an error in the design time environment. When the control is on another form, the following VS.net error occurs: '-195465169' is not a valid value for 'start'.

Here is the workaround code in my databound combobox usercontrol:
Protected Overrides Sub OnPaint(ByVal e As System.Windows.Forms.PaintEventArgs)
MyBase.OnPaint(e)
'Gets rid of the selection
If Me.ComboBox1.SelectionLength > 0 Then
Me.ComboBox1.SelectionLength = 0
End If
End Sub

I may post this as another question.