I have a tab control with a few tabs. When a tab is selected, I set the content of the tab to its corresponding view model.
I also have a DataTemplate defined for the base view model that all of the other view models derive from:
<DataTemplate DataType="{x:Type vm:BaseViewModel}">
<view:BaseView/>
</DataTemplate>
This way, my view models, which are nearly identical, will be displayed using the same base view.
BaseView is a user control. In BaseView I have an Infragistics XamDataGrid defined. It seems that only one instance of this grid is created for all of the view models, meaning I can switch between tabs as many times as I want but the user control is never recreated from scratch.
How does WPF handle the lifetime of user controls when combined with DataTemplates?
The problem I am trying to solve is that in the xaml of BaseView, I have defined a Field in the XamDataGrid like so:
<igDP:XamDataGrid.FieldLayouts>
<igDP:FieldLayout>
<igDP:FieldLayout.FieldSettings>
<igDP:FieldSettings DataValueChangedNotificationsActive="true"
AllowCellVirtualization="False"
AllowResize="True"
AllowRecordFiltering="True"/>
</igDP:FieldLayout.FieldSettings>
<igDP:Field Name="IsDirty" Visibility="Collapsed"/>
</igDP:FieldLayout>
</igDP:XamDataGrid.FieldLayouts>
The IsDirty column (all of the view models have an IsDirty property) is only correctly collapsed the first time the grid is displayed. When I click another tab, the grid's data source changes, a new FieldLayout is created by the grid, and it doesn't pick up the Collapsed setting for IsDirty. As a result the IsDirty column is visible. My thinking was if I can force the user control to be totally recreated, I could avoid this issue.
Add DataTemplate to Resources and set x:Shared="false"
Related
I am working on a an WPF MVVM application where I need to have a Main Window with just a logo and it has to show child views inside it. I don't have any controls in Main Window all the controls reside in child view for example Buttons like Next, Back, Cancel and some text blocks etc. Now If users select Next button on the child view I have to draw or load the next child view inside the Main Window. If Back button is clicked I have to go back to the previous child view. So basically I am changing the child views depending on which button is clicked. Also I am maintaining different view models for every child view. Now the problem is I am not able to figure how should I link the child views to there respective view models. This application is similar to some Installation applications where different dialogs are shown depending on the selection and the button clicked by the user.I am new to this wpf and don't want to use MVVM Light , Prism etc. Any detailed help will be greatly appreciated. Thanks in advance.
One of the easiest ways to associate any data type with XAML controls is to use a DataTemplate. Therefore, you can simply add something like this into your Application.Resources and as long as you do not set the x:Key properties on the DataTemplates, then they will be explicitly applied by the Framework whenever it comes across instances of your view models:
<DataTemplate DataType="{x:Type ViewModels:HomeViewModel}">
<Views:HomeView />
</DataTemplate>
...
<DataTemplate DataType="{x:Type ViewModels:MainViewModel}">
<Views:MainView />
</DataTemplate>
Then displaying the view is as simple as this:
<ContentControl Content="{Binding YourViewModelProperty"} />
In code behind, or your view model:
YourViewModelProperty = new MainViewModel();
It's often handy to create a base class for your view models and then the YourViewModelProperty can of that type and you will be able to interchange them using the same property and ContentControl.
UPDATE >>>
The general idea is that you have one MainViewModel class with one BaseViewModel property data bound to one ContentControl in MainWindow.xaml... the navigation controls should also be in MainWindow.xaml and not in the views themselves. In this way, the MainViewModel class is responsible for changing the property to the relevant view model instances when it receives navigation Commands from the MainWindow.xaml.
I'm using an MVVM pattern for my WPF application. If the "home" view model, which controls the layout of my application's main window, I have a ChildViewModel property. This holds a viewmodel that can be switched according to what the user is doing. When they select menu items, the child view model switches and the main area of the screen (it's in an Outlook style) switches accordingly.
I do this with a ContentControl and DataTemplate like this: (I'm only showing one of the embeddable views here to keep it short).
<ContentControl Grid.Row="1" Grid.Column="1" Margin="3"
Content="{Binding ChildViewModel}">
<ContentControl.Resources>
<DataTemplate DataType="{x:Type vm:VersionsViewModel}">
<Embeddable:VersionsView />
</DataTemplate>
</ContentControl.Resources>
</ContentControl>
I also want to add a ribbon to my main window, using the Telerik RadRibbonView control. I want this to have some fixed tabs and buttons that are always visible. In addition, I want to add and remove entire tabs, and buttons within existing tabs, according to the type of child view model. I'd like this to be done in the view in a similar manner to the way I've done the content control, above.
Is this possible? I've tried lots of things but got nowhere so far. I know I could do it by creating a huge "super ribbon" and binding visibility properties but this seems cludgey. I could also have multiple ribbons, each containing the common controls, but this would cause a maintenance problem.
In the end I went with the "super ribbon" approach, as I couldn't find any other way.
In my current scenario (WPF, MVVM), I have a user control which hosts a visio diagram. This user control is located on a view, next to a number of labels and a datagrid element.
The user control contains a DependencyProperty object SelectedNode which value is updated with the information received from the Visio diagram. The labels' content are binded so that they display the information contained in the SelectedNode (e.g. id, name):
<Label Grid.Row="1" Grid.Column="1" x:Name="lbNodeIdValue" HorizontalAlignment="Left"
Content="{Binding ElementName=visioControlUC, Path=SelectedNode.Id, UpdateSourceTrigger=PropertyChanged, Mode=OneWay}"/>
Every time I change the selection in the diagram, the label's content changes as expected.
Next to this label, I would like to display a datagrid containing information based on the id displayed in the label. This is where I ran into problems, as I can't seem to be able to get the value of the Content property of the label in the viewmodel class.
I have tried using the MultiBinding property on the Content element of the label, and creating a second binding with Mode=OneWayToSource to set the value of the label's Content to a property I have defined in the viewmodel class.
What would be a proper way to retrieve this value in my viewmodel class?
Thanks,
Adrian
Ideally your Datagrid's ViewModel should get the value of the selected label from the other ViewModel. You should not rely on Views to transfer application data between ViewModels.
It sounds like the SelectedNode value originates from the UserControl, and not the ViewModel, so you'll need to bind the UserControl.SelectedNodeId to a ViewModel somewhere so the ViewModels have access to this data
<local:myUserControl x:Name="visioControlUC"
SelectedNode="{Binding SelectedNodeId}" />
If the value is needed by more than one ViewModel, I would highly recommend some kind of event system, such as MVVM Light's Messenger or Prism's EventAggregator. This would allow your ViewModels to subscribe to something like a SelectedNodeChangedEventMessage, and the ViewModel which actually contains the SelectedNodeId can broadcast that message anytime the value changes. You can find an example of both on my blog post about Communication between ViewModels.
Just started learning MVVM. I have a tabcontrol where I am adding multiple instances of same views/pages
Dim tb As New UXTabItem
tb.Header = "Childrens"
tb.Name = "tab" & itrt
itrt = itrt + 1
tb.Source = New Uri("/Views/childrens.xaml", UriKind.Relative)
UXTabControl1.Items.Add(tb)
Since each of the same view will handle different data but since the uri is same so all the tabs get populated with same view and changes reflect on each tabs. Which should not be the case. Should I be using a separate viewmodel for each of those? Any example would be much helpful.
One of the primary goals/advantages of MVVM is that you don't create WPF UI objects in code.
You should be populating a collection of view model objects and binding the ItemsSource of the TabControl that you define in XAML to it. You should have a DataTemplate defined for the data type of those objects and put their XAML in there, instead of loading it at runtime.
The TabControl is a little tricky, because it uses two templates: the ItemTemplate is used to define the look of the tab, and the ContentTemplate is used to define the look of the tab items' content. It's pretty common to see this:
<TabControl ItemsSource="{Binding MyItems}">
<TabControl.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Text}"/>
</DataTemplate>
</TabControl.ItemTemplate>
<TabControl.ContentTemplate>
<DataTemplate>
<ContentPresenter Content="{Binding}"/>
</DataTemplate>
</TabControl.ContentTemplate>
</TabControl>
which populates the tab with a Text property on the view model, and the tab item's content with whatever template in the resource dictionary matches the view model's type.
I would have an ObservableCollection<TabViewModel> Tabs in my parent ViewModel, and bind the TabControl's ItemSource to that. Each Tab has it's own instance of TabViewModel, so adding a new Tab would mean adding a new TabViewModel to the Tabs collection in the ParentViewModel.
The TabViewModel would contain properties for things like Header or Uri, and these would be bound to the UI at the appropriate spots. Each TabViewModel can be drawn using the same View, but the data inside the object would be different for each tab.
My ParentViewModel would also contain a TabIndex property that defines which tab is selected
This is NOT trivial, IMO, and Rachel and Robert are both right.
Think of this task being one of managing 'work spaces", each represented by a tab control. I like to structure my view models into three related layers
DetailViewModel - the model for a given workspace (represented by a tab control)
MasterViewModel - the model for a collection of detail view models (ObservableCollection{DetailViewModel}). You would use this to bind to a list ion our presentation that shows what items may be selected for editing / display in a tab control. This is where filtering of the list would also be handled, if you allow that.
ShellViewModel - the model that actually has a collection of workspaces (ie, ObservableCollection{Workspace} along with the commands to manage them (ie, EditWorkspaceCommand, AddWorkspaceCommand, DeleteWorkspaceCommand). A workspace is a DetailViewModel that has a CloseCommand.
I found Josh Smith's MVVM article on MSDN useful for grokking this design.
HTH,
Berryl
I have a prism/silverlight view and it is mapped to a tabitem in a tab control of my shell.
It looks like this.
<sdk:TabControl>
<sdk:TabItem Header="User Portfolio" Regions:RegionManager.RegionName="MainRegion" />
<sdk:TabItem Header="Benchmark Portfolio" Regions:RegionManager.RegionName="BenchRegion" />
</sdk:TabControl>
The view consists of a datagrid,textbox and a button such that the datagrid maps to an observablecollection in the viewmodel and when the button is clicked, the text in the textbox gets added to the datagrid(and the corresponding collection).
Now, I want to declare multiple instances of this view-viewmodel pair. That is, in tabitem "MainRegion" I want one instance. In tabitem "BenchRegion" I want another instance
How do I do this?
You need to get the container, and for each instance of the view model you need to use IUnityContainer.ResolveType<>() to initialize the instance (Make sure you register your types first IUnityContainer.RegisterType<>()). You can think of ResolveType<>() as Prism's form of a constructor. Then for the each view you need to set the datacontext to your initialized view model for that view.
Edit I should note that this is for Prism 2.0 I know that with Prism 4.0 there are alternatives to unity.