I'm developing an MVVM WPF application and have run across another small stumbling block. In my main application window, I'm using a tabbed control as my MDI. This tab control is bound to a (observable) collection named OpenWorkspaces, which contains all the "windows" (or Workspaces in my app's language) the user has open. Here is what a "Workspace" looks like:
Public Class Workspace
Private _WorkspaceID As Integer
Public Property WorkspaceID() As Integer
Get
Return _WorkspaceID
End Get
Set(ByVal value As Integer)
_WorkspaceID = value
End Set
End Property
Private _WorkspaceName As String
Property WorkspaceName As String
Get
Return _WorkspaceName
End Get
Set(value As String)
_WorkspaceName = value
End Set
End Property
Private _ViewModelName As String
Property ViewModelName As String
Get
Return _ViewModelName
End Get
Set(value As String)
_ViewModelName = value
End Set
End Property
Private _ViewObjectName As String
Public Property ViewObjectName() As String
Get
Return _ViewObjectName
End Get
Set(ByVal value As String)
_ViewObjectName = value
End Set
End Property
Private _ViewObject As UserControl
Property ViewObject As UserControl
Get
Return _ViewObject
End Get
Set(value As UserControl)
_ViewObject = value
End Set
End Property
Private _CanSupportMultipleInstances As Boolean
Property CanSupportMultipleInstances As Boolean
Get
Return _CanSupportMultipleInstances
End Get
Set(value As Boolean)
_CanSupportMultipleInstances = value
End Set
End Property
Private _CanOpenDisconnectedFromDB As Boolean
Public Property CanOpenDisconnectedFromDB() As Boolean
Get
Return _CanOpenDisconnectedFromDB
End Get
Set(ByVal value As Boolean)
_CanOpenDisconnectedFromDB = value
End Set
End Property
End ClassHere is the Xaml for my TabControl:
<TabControl ItemsSource="{Binding OpenWorkspaces}" SelectedItem="{Binding SelectedTab, Mode=TwoWay}"
Grid.Column="1" Grid.Row="1" Grid.ColumnSpan="2" BorderThickness="0" BorderBrush="Transparent"
HorizontalAlignment="Stretch" VerticalAlignment="Stretch"><TabControl.ItemTemplate><DataTemplate><Grid><Grid.ColumnDefinitions><ColumnDefinition/><ColumnDefinition Width="10"/><ColumnDefinition/></Grid.ColumnDefinitions><TextBlock Text="{Binding WorkspaceName}" Grid.Column="0" Padding="0,1,0,0"/><Button Content="X" Grid.Column="2"
Command="{Binding DataContext.CloseWorkspace, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=Window}, Mode=TwoWay}"
CommandParameter="{Binding}"
BorderThickness="0" BorderBrush="Transparent" Background="Transparent" Padding="-4"/></Grid></DataTemplate></TabControl.ItemTemplate><TabControl.ContentTemplate><DataTemplate><UserControl Content="{Binding ViewObject}"/></DataTemplate></TabControl.ContentTemplate></TabControl>Here is my Execute (from the ICommand) routine bound to my left hand menu buttons (one for each Workspace the user has permission to) which opens a Workspace on Click:
Public Sub ExecOpenWorkspace(ByVal inWorkspaceName As String)
'Declare new Workspace variable
Dim objWorkspace As New Workspace
Dim exCreatingWorkspace As New CustomException
'Check to see if this Workspace exists in _OpenWorkspaces
If CheckForOpenWorkspace(inWorkspaceName) = False Then
'Attempt to create new workspace and check for an error
If CreateWorkspaceByName(inWorkspaceName, objWorkspace, exCreatingWorkspace) = 0 Then
'Error occurred... set consequence and inform user of error
exCreatingWorkspace.ExceptionConsequence = "Unable to launch form " & inWorkspaceName
exCreatingWorkspace.ShowErrorMessage()
Else
'Add inWorkspace to _OpenWorkspaces
_OpenWorkspaces.Add(objWorkspace)
'Set focus to new tab
'???
End If
Else
'Attempt to create the Workspace and check return value
If CreateWorkspaceByName(inWorkspaceName, objWorkspace, exCreatingWorkspace) = 0 Then
'Error occurred... set consequence and show Error
exCreatingWorkspace.ExceptionConsequence = "Unable to launch form " & inWorkspaceName
exCreatingWorkspace.ShowErrorMessage()
Else
'Need to check to see if this workspace can have multiple instances
'open at the same time.
If objWorkspace.CanSupportMultipleInstances = True Then
'Add the workspace to OpenWorkspaces collection
_OpenWorkspaces.Add(objWorkspace)
'Set focus to new tab
'???
Else
'Set Focus to the existing Tab
'???
Debug.Print(_SelectedTab.Header.text)
End If
End If
End If
End SubI'm not certain if this is relevant to this problem, but here is the code for CreateWorkspaceByName:
Public Function CreateWorkspaceByName(inWorkspaceName As String, ByRef outWorkspace As Workspace, _
ByRef outException As CustomException) As Integer
'This routine will attempt to create a new Workspace correlated to the passed in
'WorkspaceName.
'The routine will return 1 if it runs successfully, 0 if any error occurs, and will
'also pass back a workspace object through outWorkspace when successful.
'Declare variables
Dim objTempWorkspace As New Workspace
Dim objViewObject As New Object
Dim objViewType As Type
Dim exConnecting As New CustomException
Try
'Use LINQ to retrieve the passed in Workspace by Name
Dim objWorkspace = (From WorkSpace In _AvailableWorkspaces
Where WorkSpace.WorkspaceName = inWorkspaceName
Select WorkSpace).SingleOrDefault
'Attempt to connect to the database. Since the Property/Field CanOpenDisconnectedFromDB
'determines whether a Workspace can be opened without a database connection, we should
'attempt to connect now before we bother to go through with creating the workspace.
'Attempt to connect and check for error
If viewModelMainWindow.CurrentUser.EstablishUserConnection(exConnecting) = 0 Then
'No Connection. Need to check CanOpenDisconnectedFromDB
If objWorkspace.CanOpenDisconnectedFromDB = False Then
'Set outException to exConnecting
outException = exConnecting
'Return 0
Return 0
End If
End If
'I want to create a temporary Workspace object to pass back because I believe that if
'I create a ViewObject (View) for objWorkspace that it will actually store that view
'with the Workspace objects in _AvailableWorkspaces. I don't want that to happen...
'I want the application to close and recreate the ViewObject every time the user
'closes or opens a form and I also don't want the memory overload of my menu class objects
'storing Views.
objTempWorkspace.WorkspaceID = objWorkspace.WorkspaceID
objTempWorkspace.WorkspaceName = objWorkspace.WorkspaceName
objTempWorkspace.ViewObjectName = objWorkspace.ViewObjectName
objTempWorkspace.ViewModelName = objWorkspace.ViewModelName
'Use GetType to cast object as new View from ViewObjectName field
objViewType = Type.GetType("CoreTimeClock." & objTempWorkspace.ViewObjectName, True, True)
objViewObject = Activator.CreateInstance(objViewType)
'Add objViewObject to objWorkspace
objTempWorkspace.ViewObject = objViewObject
'Return objTempWorkspace
outWorkspace = objTempWorkspace
'Return 1 to indicate success
CreateWorkspaceByName = 1
Catch ex As Exception
'Return 0 to indicate failure
CreateWorkspaceByName = 0
'Set CustomException properties
outException.IsCustomException = False
outException.ExceptionObject = ex
outException.AttemptedAction = "attempting to create form " & inWorkspaceName & "."
outException.GeneratedBy = "viewModelMainWindow"
outException.GeneratedByRoutine = "CreateWorkSpaceByName"
'Log Error
outException.LogError()
End Try
End Function So, if you look at ExecOpenWorkspace, my comments indicate what my problem is. When I create a new Workspace (which is a TabItem on my TabControl), it gets created just fine, but doesn't get "focus". Also, I want the result of clicking a button for a Workspace (which can only be opened once) that is already opened to be for it to receive "focus". On a different form, I was able to do "on demand loading" of the individual tabs of a tab control by binding to "SelectedItem". However, that TabControl isn't dynamic like the one for my main window, which I think makes a big difference because "SelectedItem" always seems to be Nothing. In other words... my "Debug.Print" line always generates an exception.
Any ideas on how to accomplish setting focus with my dynamic tab control? As always, thanks in advance for the help! The guidance I've received from the MSDN community has been absolutely invaluable :).