I am little confused about how to create Master Detail view with two different user controls.
There are three choices,
Choice 1
CustomerMasterView + CustomerMasterViewModel
CustomerDetailView + CustomerDetailViewModel
And keep both View Models in App.Resources
But by doing this, binding becomes complex with all static resources source markup code.
Choice 2
CustomerViewModel
CustomerMasterView
CustomerDetailView
Both views share same ViewModel via App.Resources, well even with the binding code has too many items.
Choice 3
CustomerMasterView + CustomerMasterViewModel
CustomerDetailView + CustomerDetailViewModel
Both view's have DataContext set to their corresponding ViewModel. Now here is the little issue,
CustomerMasterView has Selector (ListBox or DataGrid or whatever), whose SelectedItem needs to be bound to CustomerDetailViewModel's "Customer" Property as two way binding.
Does it look good?
<!-- CustomerMasterView -->
<ListBox
ItemsSource="{Binding CustomerList}"
SelectedItem="{Binding DataContext.Customer,ElementName=customerDetailView}"
/>
<local:CustomerDetailView
x:Name="customerDetailView"
/>
But by doing this, I am defying purpose of ViewModel as it adds more dependency in my UI code.
Which one is most preferred way or is there any other way?
Should I create nested View Models?
I am also trying to learn Prism, and I have little confusion of how to do this right, any help will be appriciated.
The simplest appraoch in my opinion would be to have a single view model, with two UserControls.
Your ViewModel would have your list of customers, as well as a "ActiveCustomer" or "SelectedCustomer". Your MasterView (with the DataContext set to you ViewModel), would contain your list, wired up like this:
<ListBox ItemsSource="{Binding Customers}" SelectedItem="{Binding ActiveItem, Mode=TwoWay}" />
Your MasterView will also include your DetailsView (another UserControl). It looks like this:
<views:DetailsUserControl DataContext="{Binding ActiveItem}" />
You might be interested in the BookLibrary sample application of the WPF Application Framework (WAF). It shows how to implement a Master/Detail scenario with two Views (separate UserControls) and two ViewModels.
Related
I am new to MVMM Light toolkit (note, I'm using Light on .NET 3.5). So far I am really starting to like the pattern save for two challenges.
I'd like to have reusable XAML templates for certain types of pages in my application. Think of a movie ticket kiosk. Main content in the center but almost always a button somewhere on the screen to cancel or go back. I'd like to have reusable grid(s) where when I create a new page I basically import that grid layout and don't have to worry about the common bits and can just focus on my part. Doing a little research I feel like <ContentPresenter> might be the way to go here but it's still foreign to me.
Assumign I succeed in my first challenge, I would think the data context for those common items (say a Cancel button) would be somewhere else other than that page's ViewModel to avoid a bunch of duplication of code. Is that best approach to take the individual controls and reference a different view model from the XAML? Something like...
<Button ... DataContext={Binding CommonStuffVM, Source={StaticResource Locator}} />
You can use Templates or DataTemplates to create a reusable template defining how an object should look.
For example,
<DataTemplate DataType="{x:Type local:MovieTicket}">
<!-- Write the XAML for your Movie Ticket -->
</DataTemplate>
You can give your DataTemplate an x:Key to reference it specifically in an ItemTemplate or ContentTemplate, or leave it out so it will be used anytime WPF tries to draw a MovieTicket object
<ItemsControl ItemsSource="{Binding MovieTickets}" />
<ContentControl Content="{Binding SelectedMovieTicket}" />
For your second question, I think this would be a bad idea for individual controls, although its a common practice for complete sections of the program.
When using MVVM, your ViewModels are your application, not your UI.
If your window should display a list of Movies for the user to edit, and allow the user to Save or Cancel their changes, then your ViewModel should contain an ObservableCollection<Movie> and contain an ICommand SaveCommand and ICommand CancelCommand
You really want your View to only reflect your ViewModels, and not have them pulling the data they need from all over the ViewModel hierarchy.
Based on your question, you may be interested in a blog article I have about Navigation with MVVM which uses code very similar to what you're asking about. It shows how to change the UI using implicit DataTemplates, and contains a complete code sample that you can download and look at to get a better idea of the MVVM architecture.
I have an application that uses Caliburn.Micro. My View contains a user control which contains e.g. a tab control. I want to be able to access that tab control from the outer ViewModel to select a particular tab. Is it possible?
Thanks.
The standard MVVM way is to have the TabControls SelectedItem property bound to a property on your viewModel.
<TabControl ItemsSource="{Binding PropertyToYourViews}"
SelectedItem="{Binding PropertyToYourSelectedView}">
</TabControl>
If you do it this way your ViewModel does not have to know about the existence of the TabControl.
The next step is dependant on your implementation. Your outer ViewModel could simply keep a reference to the child viewModels SelectedView property and access it directly however,
If you want to keep your ViewModels decoupled then you will need to implement some sort of notification system. I'm not sure of the specifics of Caliburn.Micro but most MVVM frameworks offer some kind of solution for this.
Implementation would depend on exactly how you have it set up, but you can bind a variable in your view model to the SelectedItem of the TabControl
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 collection of objects that I want to present. How can I do this? A listbox would do but each object has many attributes which I want to present. I already bound a listbox to a collection and I have all my objects listed. My question is regarding the visualization of the listbox and if the listbox is the correct thing to use or there is something else that I should use.
I find the existing answers to be a bit lacking, normally one would not process collections or boil their items down to a string, at the very best you would do some dynamic manipulation using a CollectionView (e.g. sorting, grouping), but normally you use Data Templating to display the individual items which allows you to use all their properties.
Further there are several controls which work well with collections, firstly you need to know if you want selection, if not an ItemsControl is a good choice, otherwise you should use a ListBox or ListView.
ListViews are normally employed if you have different views for your objects, e.g. a details view and a thumbnail view. You can use the ListView.View for this, there is one existing view in the framework, the GridView, which offers columns. What Matthew Ferreira suggested is exactly what you should not do with a ListView since you want to make the templates dependent on the current view, in fact that code does not even compile since DataTemplate can only have one child.
ListViews are supposed to encapsulate the view logic in their view so it can be changed at will. If you decide to use a ItemsControl or ListBox then setting the ItemTemplate is what you want to do. Read the Data Templating overview i linked to, it makes for a good starting point.
You might want to consider using a ListView control instead. ListView has support for columns if you are planning on showing several properties from your object. You can use the ItemTemplate property to format the display of your object. For example:
<ListView ItemsSource="{Binding Path=myObjectCollection}">
<ListView.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Path=Title}"/>
<CheckBox IsChecked="{Binding Path=ShouldCheck}"/>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
This example assumes that your object has the properties Title and ShouldCheck.
Your collection of object is probably to be viewed as your model. The usual thing in WPF is to add a ViewModel that translates and exposes the model data into a form suitable for binding. Depending on what you want to do, your VM could e.g. format each object into a string representation and then expose it as a collection of strings that the Listbox can bind to and display.
I feel mysefl confused about how to implement view switching when view model changes. Example of what i'm tring to do:
The control I want to make is something like a wizard control. I have a list of view models added to collection of wizardsteps, and a current item viewmodel. How to display the view of active view model and switch them then active view model changes? How do I bind them?
In WPF I'd use DataTemplate but Silverlight doesn't support x:Type.
<DataTemplate DataType="{x:Type ViewModel1}">
<view:View1 />
</DataTemplate>
<DataTemplate DataType="{x:Type ViewModel2}">
<view:View2 />
</DataTemplate>
I think a wizard is a case where you should have one ViewModel for multiple Views.
You could control the visibility of each view with Properties (IsPage1Visible, IsPage2Visible,...), Commands (PreviowsPageCommand, NextPageCommand, CancelComamnd) and all logic in only one VM.
Put all "pages" of the wizard in one UserControl and bind the visilitiy of each with the boolean properties and a BooleanToVisibilityConverter.
Check this out, it talks about non-linear navigation in SL/WPF and how to maintain state. http://karlshifflett.wordpress.com/2010/07/07/non-linear-navigation-in-silverlight-4/