I am in the process of translating a Forms user control into a WPF user control. In my forms version do i overwrite a method called CreateHandle, where i hook up some events. I am having problems translating this to WPF as it do not have a CreateHandle method to overwrite, and i have been unable to figure out what else to overwrite. I am not able to do it in the constructor as the events i want to hook up is have not been created at this point.
Update: What i would like to do it have a method that is executed in WPF roughly at the some time the CreateHandle method in a forms user control would have.
Found a way to do it.
Public Sub New()
' This call is required by the designer.
InitializeComponent()
AddHandler Me.IsVisibleChanged, AddressOf OnView
End Sub
Private Sub OnView(ByVal sender As Object, ByVal e As DependencyPropertyChangedEventArgs)
' Do stuff here
RemoveHandler Me.IsVisibleChanged, AddressOf OnView
End Sub
Related
I have a wpf Custom Control which is now raising custom events. In a test project that I have created to test the ongoing development of the control I have placed a copy of my new custom control on the main window.
In the properties dialog for said control I can see my new event and I can type in the name for a handler for it in the code behind the main window and it's not only created for me but when I place a break point on it I see both the sender and my own event args raised in the control.
What I would now like to know Is what is the correct way to alert a viewmodel about that event respecting the principles of MVVM.
Below is the xaml markup for my custom control in the mainwindow of the test application
<WpfControls:VtlDataNavigator Name="vtlDn"
ItemsSource="{Binding Path=Orders}"
Grid.Row="1"
AddButtonVisibility="True"
CancelNewRecordButtonVisibility="True"
SaveButtonVisibility="True" />
The event I want to catch is called 'RecordControlButtonClicked' and this is the event automatically created in the mainwindow code behind
Private Sub MyCustomHandlerForControlEvent(sender As Object, e As ViewToLearn.WpfControls.VtlDataNavigatorEventArgs) Handles vtlDn.RecordControlButtonClicked
End Sub
So now what I'm after is the correct syntax in both the xaml and my new MainWindowViewModel to have this event transferred across to the viewmodel for handling (or suggestions as to the most efficient way to do this idf there is no direct route.
FYI I already have a relay command set up in the test application but the way that I've used it to bind commands in the past doesn't appear to be working with events.
Edit
One approach I've tried which appears to work is to add the following in the code behind of the main window's loaded event.
Class MainWindow
Public Sub New()
InitializeComponent
DataContext = New MainWindowViewModel
End Sub
Private Sub MainWindow_Loaded(sender As Object, e As RoutedEventArgs) Handles Me.Loaded
Dim mvm As MainWindowViewModel = DirectCast(DataContext, MainWindowViewModel)
mvm.vtldn = vtlDn
End Sub
End Class
and then add the following in the viewmodel;
Private _vtldn As ViewToLearn.WpfControls.VtlDataNavigator
Public Property vtldn As ViewToLearn.WpfControls.VtlDataNavigator
Get
Return _vtldn
End Get
Set(ByVal Value As ViewToLearn.WpfControls.VtlDataNavigator)
If (_vtldn Is Value) Then Return
If Not IsNothing(vtldn) Then
RemoveHandler vtldn.RecordControlButtonClicked, AddressOf MyCustomHandler
End If
_vtldn = Value
If Not IsNothing(vtldn) Then
AddHandler vtldn.RecordControlButtonClicked, AddressOf MyCustomHandler
End If
RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(NameOf(vtldn)))
End Set
End Property
Private Sub MyCustomHandler(ByVal sender As Object, ByVal e As VtlDataNavigatorEventArgs)
'this does get called when buttons in the custom control are clicked
End Sub
However I'm acutely aware that this is not really 'pure' mvvm so if there are better ways to do this I'm open to suggestions.
I've created a custom control called ecTextBox in VB.NET which uses a control template in Generic.xaml. That works.
In code behind of the custom control I override metadata in the constructor:
Public Sub New()
DefaultStyleKeyProperty.OverrideMetadata(GetType(ecTextBox), New FrameworkPropertyMetadata(GetType(ecTextBox)))
End Sub
In MainWindow.xaml I use the custom control with a simple
<ec:ecTextBox/>
That works fine.
But if I throw a second control or change the propertys of the first ecTextBox in MainWindow.xaml, I get the message "PropertyMetaData is already registered for type ecTextBox".
In StackOverflow I've read, that C# programmers should use the static-Keyword for the constructor. But if I change the constructor to
Shared Sub New
DefaultStyleKeyProperty.OverrideMetadata(GetType(ecTextBox), New FrameworkPropertyMetadata(GetType(ecTextBox)))
End Sub
the second custom control don't uses the control template but appears as a normal TextBox without Border.
What is the correct way to override the metadata for all used ecTextBox controls and prevent the errors?
This is the solution:
Public Sub New()
MyBase.New()
End Sub
Shared Sub New()
DefaultStyleKeyProperty.OverrideMetadata(GetType(ecTextBox), New FrameworkPropertyMetadata(GetType(ecTextBox)))
End Sub
We have a few scenarios in our WPF/MVVM application where a window is being instanciated and opened within the confines of a method. Very simplistic example:
Private Sub subOpenWindow
Dim myViewModel = New Viewmodel1 'create viewmodel that Window1 will use as datacontext
AddHandler myViewModel.SomeEvent, AddressOf subHandleSomeEvent
Dim myWindow = New Window1(ViewModel1)
myWindow.Show
End Sub
Private Sub subHandleSomeEvent
'do some stuff
End Sub
Now - we are debating whether or not the use of an AddHandler without a subsequent RemoveHandler (normally a big no-no) is causing us memory issues given that the AddHandler declaration is decalred and used inside of the subOpenWindow method and there is no obvious means of performing a RemoveHandler call. We could move the viewmodel declaration to a more global level but this does not seem as clean.
The question is: is a RemoveHandler necessary in this scenario? Or will garbage collection clean up properly once the window has been closed?
You could handle the Window's Closed event to remove the handler. As it is, the reference created by the current class (the one containing the handler) does indeed keep myViewModel in memory. An alternative would be to look into using weak events - see here for details.
I created a usercontrol with a treeview inside it. The treeview will be populated if I add nodes in the onload handler of the usercontrol. But after that(for example, I click a button in its parent form), the treeview will not refresh. I can see the nodes was updated in memory, but it just cannot display on the screen. I called refresh/update after adding nodes. Any suggestion is appreciated.
I put a quick test together based on your description and it seems to paint just fine.
UserControl1
<Global.Microsoft.VisualBasic.CompilerServices.DesignerGenerated()> _
Partial Class UserControl1
Inherits System.Windows.Forms.UserControl
'UserControl overrides dispose to clean up the component list.
<System.Diagnostics.DebuggerNonUserCode()> _
Protected Overrides Sub Dispose(ByVal disposing As Boolean)
Try
If disposing AndAlso components IsNot Nothing Then
components.Dispose()
End If
Finally
MyBase.Dispose(disposing)
End Try
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()
Me.TreeView1 = New System.Windows.Forms.TreeView
Me.SuspendLayout()
'
'TreeView1
'
Me.TreeView1.Dock = System.Windows.Forms.DockStyle.Fill
Me.TreeView1.Location = New System.Drawing.Point(0, 0)
Me.TreeView1.Name = "TreeView1"
Me.TreeView1.Size = New System.Drawing.Size(150, 150)
Me.TreeView1.TabIndex = 0
'
'UserControl1
'
Me.AutoScaleDimensions = New System.Drawing.SizeF(6.0!, 13.0!)
Me.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font
Me.Controls.Add(Me.TreeView1)
Me.Name = "UserControl1"
Me.ResumeLayout(False)
End Sub
Friend WithEvents TreeView1 As System.Windows.Forms.TreeView
End Class
Public Class UserControl1
Public Sub AddNewNode(ByVal text As System.String)
TreeView1.Nodes.Add(text)
End Sub
End Class
Put the usercontrol on a form with a button
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
UserControl11.AddNewNode(Now.ToString)
End Sub
End Class
If you are seeing proper painting as well then look at any graphics handling in the parent form then the usercontrol then the controls within the usercontrol. We really need more info.
Thank you, Dave. I figured it out. I put the usercontrol twice to my form by mistake(I cannot remember how I did it). And the one I operate is underneath the other one. That's why I cannot see it. Sorry for wasting your time.
In order to take advantage of the spell checking ability of WPF textboxes, I have added one to a user control (with the use of elementhost). This user control is used in various window forms. My current problem is trying to handle keyup events from this textbox but the windows form is unable to "get" any event from the control. I can access the properties of the textbox just fine (i.e. text, length, etc.) but keyboard events don't seem to work.
I have found, however, that the following will bring back events from the WPF textbox:
Public Class MyUserControl
Private _elementHost As New ElementHost
Private _wpfTextbox As New System.Windows.Controls.Textbox
Private Sub MyUserControl_Load(...) Handles Me.Load
Me.Controls.Add(_elementHost)
_elementHost.Dock = DockStyle.Fill
_elementHost.Child = _wpfTextbox
Dim MyEventInfo As EventInfo
Dim MyMethodInfo As MethodInfo
MyMethodInfo = Me.GetType().GetMethod("WPFTextbox_KeyUp")
MyEventInfo = _wpfTextBox.GetType().GetEvent("PreviewKeyUp")
Dim dlg As [Delegate] = [Delegate].CreateDelegate(MyEventInfo.EventHandlerType, Me, MyMethodInfo)
MyEventInfo.AddEventHandler(_wpfTextBox, dlg)
End Sub
Public Sub WPFTextbox_KeyUp(ByVal sender As Object, ByVal e As RoutedEventArgs)
' something goes here
End Sub
End Class
The user control is now able to do something after the PreviewKeyUp event is fired in the WPF textbox. Now, I'm not completely sure how to have the window form containing this user control to work with this.
Im a C# person not VB so please bear with me.. Basically you could assign the event from your Window rather than within your UserControl.. So in the constructor of your Window assign the PreviewKeyUp:
this.myUserContorl.PreviewKeyUp += new System.Windows.Input.KeyEventHandler(WPFTextbox_KeyUp);
then place the event handler in your Window:
private void WPFTextbox_KeyUp(object sender, System.Windows.Input.KeyEventArgs e)
{
}
Incidentally you needn't go through the hassle of capturing the event in your UserControl as you can still access your TextBox within you UserControl directly from your Window (if you make it public), again from your constructor in your Window:
this.myUserContorl.wpfTextbox.PreviewKeyUp += new System.Windows.Input.KeyEventHandler(WPFTextbox_KeyUp);
I imagine it would look like this in VB (at a guess):
AddHandler myUserContorl.wpfTextbox.PreviewKeyUp, AddressOf WPFTextbox_KeyUp
ElementHost has a static method called EnableModelessKeyboardInterop(). Try calling it?
ElementHost.EnableModelessKeyboardInterop();
Read more here
Seems basic, but did you set the KeyPreview to TRUE on your form?