I want to create an application where the user navigates through pages that are placed inside a frame element. The problem is that one page can have different layouts which basically provide the same functionality. There can be a few buttons or input controls more or less per layout, but they all should share the same code behind file.
In Windows Forms, I used to place all elements (the layout) on the same form and then hide/show the controls I required, but that's a very ugly solution and I was hoping that WPF provided something more convenient here.
I tried to create 2 Pages, deleted their respective .cs files and set their "x:Class" attribute to a custom .cs file, but that results in compiler errors (ambiguous calls to InitializeComponent() ).
So can I have multiple pages that share the same code?
You should move the logic from the code-behind class to a view model class. This pattern is known as Model-View-ViewModel and is the recommended design pattern to use when developing XAML based user interface applications.
There are plenty of online tutorials about it and this one should provide a good starting point for you: https://msdn.microsoft.com/en-us/library/hh848246.aspx.
Once you have understood the pattern and implemented your application logic in a view model class, you could then simply set the DataContext property of both pages to the same view model:
public Page1()
{
InitializeComponent();
DataContext = new ViewModel();
}
A code-behind class is simply a partial class, i.e. it is partial definition of the Page that you define in XAML and therefore you cannot "share" this one between several different pages.
Partial classes are just a way of splitting the definition of a class across several different source files: https://learn.microsoft.com/en-us/dotnet/articles/csharp/programming-guide/classes-and-structs/partial-classes-and-methods.
Related
I've got standard MainWindow.xaml. Then I added some pages which I wanted to show in the MainWindow. There are some common elements for all views, for example, header text, header image, and the name of logged user. How can I set these elements on the MainWindow that will be visible when another view is shown?
Set the appropriate items in the resources.
Properties that need these values will be able to get them using DynamicResource.
But it will be much better if you implement the Solution in the MVVM pattern.
Then you won't even have such a task (to transfer data between views).
I'm kind of a beginner with the WPF platform. I've done a few Windows Forms apps that were very basic and now I'm working on a much more complex app for my current work.
I'd like to implement an MVVM model, but I'm getting lost in the different articles on how to do so.
Here's a screenshot of the app interface:
The section on the left is a ListView containing 6 sections that correspond to different UserControl. I would like the section on the right to display the UserControl that corresponds to the selected Item.
Each UserControl is stored in a separate XAML file.
By looking online, I found that I should use a ContentControl in my MainWindow, but every attempt I've made has been unfruitful. I know there's more than one way to skin a cat.
Which method would you use? Do you have any concrete examples or sources where I can find how to make it work?
The only difference between UserControl and ContentControl is the OnCreateAutomationPeer method. This method is responsible for UI automation.
Although this method is rarely used in practice, it is customary to use UserControl to represent some complex data types.
A typical use for a UserControl is to retrieve data (in normal CLR types) through the data context.
And the Content property specifies (using XAML) a visual tree to represent that context.
And each such UserControl is declared as a derived type (just like a Window).
If necessary, additional properties (CLR and DP) and other members (event handler methods, for example) are added to such a UserControl.
The base class ContentControl itself and others of its successor are used somewhat differently.
The data in them goes directly to the Content property.
And their visualization is set by the data template in the ContentTemplate property.
While DataTemplate's can be quite complex, they are usually much simpler than the XAML markup of the UserControl.
And, besides the task of visualization, you cannot add additional logic (properties, fields, methods).
Here's a photo of the app interface: ...
In this UI, I don't see where the ContentControl can be applied.
On the left is a navigation bar consisting of buttons.
It is usually implemented directly in the Window from an ItemsControl or ListBox.
On the right (while an empty area) is the region for the page content.
Usually, when you click on a button in the navigation bar, the corresponding UserControl is set to this region.
At a lower level, deeper in the visual tree, for smaller elements, it is quite possible that a ContentControl is needed.
P.S. Just in case, I will clarify, in view of the comment below.
By area for pages, I do not in any way mean the use of Frame + Page.
This is a very specific pair and it is extremely rarely justified to use it.
In combination with MVVM, its use is even more difficult, since this pair does not support DataContext inheritance.
And this is the main way for the View to interact with the ViewModel.
My project using MVVM design pattern using Prism and Unity, basically following the famous Prism video by Brian Lagunas, but the video didn't mention how to create/use partial view, User Control used in other User Controls.
I'm trying to create custom partial view(UserControl) can be reused in other page (User Control). For example, a View contains a "Browse" button Binding SelectFileCommand and Publish the file Path when done. If I have two of this View in one page, how can I subscribe to the correct command? Both Commands called same name.
For using Partial View:
Register View Type in Module like this:
container.RegisterType<IPartialView, PartialView>();
and use the view directly in page like this:
<views:PartialView DataContext="{Binding PartialViewModel}" />
I'm not sure if this is the correct way to implement Prism MVVM pattern. Please let me know if this is the wrong idea, and how to implement these kind of Partial View.
Thanks a lot.
I'm not sure I understand what you need but I'll give it a try.
If your partial view is in another module, first, you can't use elsewhere than in this same module. You could use some IPartialView, but I'm not sure this is needed here, Prism gives much simpler solutions.
The simplest way to do what I think you want to do would be to have a region where you want to have your partial view. You would use RegisterViewWithRegion in the module definition to register the PartialView against the corresponding region(s).
That way, if you have this partial view several times, you will have several regions with the same name, and only one registration of PartialView in the module. Just give the right DataContext to each region.
Okay, so I am working with Microsoft Prism in WPF using a MVVMC(or MVCVM) pattern.
In my ChatModule I have a series of Views, ViewModels, and one Controller.
For the Views I have
ChatAreaView - Displays the chat messages that come in to be read. This is hosted inside of a TabControl region so that I can have chat windows between the user and other users, or maybe file transfer windows, etc.
UserAreaView - This is a list of the users. Right clicking has context menu to interact with them... like sending a file or whispering.
MessageAreaView - This is where the user types in messages to be sent to all of the others.
For each view, I have a corresponding ViewModel. ChatAreaViewModel, UserAreaViewModel and MessageAreaViewModel. These ViewModels essentially only contain properties.
For example, the UserAreaViewModel defines a struct of type User which is essentially just a Name. Actually this is defined outside of the class, but still... it uses it. It has an ObservableCollection to store a list of all the Users who are currently connected. It also has ICommand properties defined to interact with the user. Right now I have SendFile, Whisper and Nudge... with intent on adding more in the future.
The Controller creates these views and ViewModels, and marriages them. It news them up, assigns the ViewModel as the corresponding View's DataContext, and sets all the initial properties of the ViewModel. Over the lifetime of the module, it will react to user interaction and execute DelegateCommands that it has assigned to each of the ViewModel's ICommand properties. These will further alter the state of the properties in a ViewModel.
I am using the actual types of Views and ViewModels, instead of interfaces, like such.
#region Views
ChatAreaView viewChatArea;
UserListView viewUserArea;
MessageView viewMessageArea;
LoginPromptView viewLoginPrompt;
#endregion
#region ViewModels
ChatAreaViewModel viewModelChatArea;
UserAreaViewModel viewModelUserArea;
MessageAreaViewModel viewModelMessageArea;
LoginPromptViewModel viewModelLoginPrompt;
#endregion
Would things be a lot more neat, less coupled if I defined interfaces for the Views and ViewModels, and operated on these interfaces within the controller instead of the concrete implementations? Could I then just register them with my Container in the Module class(which is essentially the root of each Module)?
What do I have to gain from doing this? How would I implement an interface for each view to distinguish them from the others? They don't really do ANYTHING except have XAML... and teh ViewModel's don't really do anything either except have certain properties. And those properties might be subject to change. On the UserAreaViewModel for instance, I will definitely want to add more commands so a user can interact with another user in different ways.
Can somebody help me out here? In my mind I'm thinking I should be abstracting this stuff, but I don't really know a logical way I should be going about it, or even if it's a wise idea to do so. What do I have to gain?
Thank you for your time. The below image is an example of what I'm working on. Ignore the Add new Item button and the styling of everything... that's not what I'm working on right now.
loosely coupled - can replace an entire class with altogether different implementation in future.
independent development.. can inject a dummy UI / view until final UI gets ready. two pieces can evolve at the same time (after having a common contract).
no need to add references to the modules (implementing the view). can use ConfigurationModuleCatalog to discover types from config file.
Bear with me because I'm new to WPF/XAML. I'm trying to write a MainWindow.xaml / App.xaml pair that properly isolates stylization and data binding, as close to a model-view-controller as possible. So far:
I have a styles.xaml that contains all of the formatting (fonts, margins, etc.). It's referred to from app.xaml's Application.Resources so that it can apply to all WPF forms in the project.
Model data collections exist as member variables of App, and App exposes them via GetX() acccessor functions.
mainwindow.xaml contains the view structure, as well as binding information. This is done like so:
ObjectDataProvider x:Key="AppX" MethodName="GetX"
ObjectInstance="{x:Static local:App.Current}"
The fact that mainwindow.xaml contains binding information is bad, since that should be the role of the controller (app). Unfortunately, I've found out that one of the restrictions of the WPF designer is that you can't (for instance) have two unkeyed Resources references (one for view styles, one for data binding styles). Similarly, app.xaml can't contain both the styles.xaml reference and a set of data binding styles in its Resources section.
I could theoretically manually instantiate the main window from the app's startup handler, and then do the binding in code, but that would violate the spirit of WPF in two ways - the app shouldn't need to make the window, as that's done in the background; and binding is better done in XAML than in code when possible. If there were a way for the app to be notified that the main window has been created so that it can then do binding, that wouldn't be bad, but I haven't seen any (short of the main window calling the app after load, but that shouldn't be the responsibility of the view).
So I'm kind of out on a limb. I don't know of a way to properly adhere to MVC while still doing things "the WPF way" - it seems that the default is for the VS designer to create a monolithic window XAML that has a mishmash of view, view stylization, and controller. Any descriptions on how to do this better or links to good websites on the topic will be appreciated.
MVVM is essentially MVC. In MVVM there is an extra seperation of the View into a view and view model where the view now is merely the controls of the UI and the view model holds the data and logic of the view. Additionaly, in MVVM, the relationship between the View and View Model, in isolation, can also be seen as the MVC pattern where M = ViewModel, V = View, C = DataBinding.