I'm new to WPF and MVVM and attempting to write a firmware programmer so I can update stuff via USB and save and upload setting/state data. MVVM seems like it could work for this. I currently have pages and can navigate around the app (although the nav service is in code behind for now) but I'm stuck on how to implement things that aren't in the standard 'customer'/'person' examples.
On a couple of pages, there are subsections that I can see being sub-divided into separate views hosted in the page, and these subsections are used more than once in the app.
For instance, I want to have a TextBlock that displays the connection status and updates based on signposts in the connection process, firmware update, backup, etc. Progress bars with the % are another. Sections that are used to display errors, data or a selection box depending on what happens connecting would be another.
Having a sub-section house 3 completely different outputs all stacked on top of one another and shown based on the situation seems messy. I can see that section being a ViewBox and creating a unique view for each case being a better solution there (and possibly the other examples above).
Or take the 'status display', I can see implementing it as it's own view and the page's view model will use a messenger to pass the current status back to the 'status display' view model. I can also see it all just handled by the page's view model via calls to it's own methods. I can also see potentially using a global model to hold the status strings (maybe an enum?) and the view model can be made to pull the correct string into a 'currentStatus' variable.
What is the proper way to approach this? Keep it all a single page? Subdivide the dynamic/changing parts from the static parts?
OP:
Obviously the pages themselves are views, but would it be best to have the 'Status:'display TextBlock and it's value, and the Error/selector section be views also?
If you are asking whether the status and error displays should be UserControls then yes they can be "a view" irrespective of whether the control is using a view model or not.
Incidentally, it is generally better to use DependencyPropertys instead of view models in a UserControl otherwise you will end up having duplicate properties in both the view (so that MainWindow can databind to it) and in your control's view model (purely for the benefit of the user control).
If your UserControl uses DependencyPropertys then both users of the control and your view can both databind to the same set of properties without duplication. In this way you will realise that UserControls have no need for a separate VM.
OP:
...the page's view model will use a messenger to pass the current status back to the 'status display' view model...
Don't do this, this is what data binding is for.
I currently have a Ribboncontrol on top of my main window. On the Ribboncontrol there are several RibbonPages and depending on which RibbonPage is selected I want to display below the RibbonControl a different IDE Layout that suits the need of the chosen RibbonPage.
Is my approach correct that I create different views/viewmodels for each IDE layout and that with each different RibbonPage that is selected a corresponding view/viewmodel is perused? I like to use this approach because then I would not need to communicate between views/viewmodels because the functionality in each RibbonPage is self-contained.
Each view would be a UserControl that encapsulates a DockLayoutManager. I included some screenshots below (SS1 = MainWindow onto which I want to load different views; SS2 = the view that represent a UserControl that in turn represents a DockLayoutManager with all associated LayoutPanels, DocumentPanels, ....)
Question: How would I go about implementing that and is that a workable solution to display different views as a function of the chosen RibbonPage?
It is common to display different view pages that relate to different functions and or tabs of a RibbonControl. Typically you'd have a base view model class that all of your view models extend and a property of that type in your parent view model... let's call it YourViewModelProperty. To change the view, you'd just need to set a new view model to that property:
YourViewModelProperty = new SomeDerivedViewModel()
You can link each UserControl to its related view model in DataTemplates declared in App.xaml. In this way, they'll all be available to every view in the application. You can find out more information regarding this method in my answer to the WPF - automatic view resolving for view model question here on Stack Overflow.
UPDATE >>>
There is a much better explanation available in my answer to the WPF MVVM navigate views question.
I have 2 different layouts in my project that based on the view that is called, I will tell the view which layout to use. I'm having an issue where my first layout is rendered (my landing page), I render a certain set of scripts/styles. Once I want to render my 2nd layout, the browser is holding on to all the styles/scripts from my previous layout. Is there anyway to decouple those scripts/styles when changing layouts?
Never mind, I'm dumb. I forgot to change one of my script and style render strings. Once I put the right one in it works.
The problem I'm facing is that, I'm unable to access a control(button) which is in the MenuPanoramaPage.xaml from another page which is MyProfile.xaml.
I wanted to change the content within the button when I select the radio button which is in the MyProfile.xaml. How could I make this?
I tried using this within the button tag in xaml:
x:FieldModifier="public"
But it didn't work out. How can I work on this?
Thanks in advance.
I suggest you to use MVVM Pattern in which use can handle these kind of problems like handling data of one page from other page.
I give you a simple scenario :-
Suppose you want to change the content of a button that is on another page then what you have done basically is.
Some Points :-
1- > Define a string property in viewmodel of the page that contain button. and bind this property to the content property of the button.
2 -> So suppose you want to change it from other page then all you have to do is send a message from another page to change this property. And it will be automatically updated on button(you will get it after some example setup).
3 -> It is not related to some simple string contents. You handle whole data that will be displayed on that page and other View related properties too.(Basically MVVM is much more powerful than you can thought of).
4 -> Last point If you want to make a quality Windows Phone app then MVVM pattern is a good fit.
Links :-
How to implement MVVM in Windows Phone
Basic one from Channel9
What actually MVVM is ?
Explore those. You will not regret. Cheers :)
Sorry, but this is not possible. You only have direct access to the controls on the page you are on. In this case you can only change the controls in MyProfile.xaml.
But what you could do is sending an event or message (if you are using mvvm) to the MenuPanoramaPage.xaml / ViewModel.
I still don't get the primary purpose of Html.Action in asp.net mvc. I have been using Html.Partial every time I need to load up a partial view or wanted to split up some code in a view to clean it up.
Where does Html.Action fit into all of this (e.g. where would you want to use Html.Action and not use Html.Partial)?
Edit
The answers seem to be use Html.Action for dynamic data. I don't get this as you can use Partial Views for Dynamic data as well.
For instance if a user on my site edits a row. A ajax call is made to a method and I go grab that row from the db. I then return a parital view of a form that has all the data on it ready for editing. If an error occurs then I return a json result with the error method and my javascript consumes it and alerts the user.
If all is good then the rendered html is put into a jquery dialog and displayed to the user.
Is it because you can use the "ChildActionOnlyAttribute" that makes people use Action instead?
Ankur has the right idea but I find you can really simplify the concept down further.
For me it comes down to What versus How
If you know what you want to render but not how it's likely you'll use a partial to let it determine how to render the information.
For example, maybe your view model is for an invoice. Your invoice view model probably already has all the information you need about the invoice itself, including an enumerable of the line items on the invoice perhaps. A partial might be a good choice for the line items so that it's self contained. You already have the line items details (the what), but a partial will handle how it gets rendered (the how)
On the flip side, maybe your invoice view model has a customer ID on it but no actual customer details. Here you don't have the what, so you'd pass in the customer ID to an Action and it'll get what data it needs and pass it off to the view to render how it seems fit.
So in summary if you already have all the data you want to work with, just stick with a Partial, but if you are missing information that you need to obtain, Action would be better.
Where this get really fuzzy around the edges is when a Partial view includes the ability to retrieve it's own data via Ajax (or other technologies). In which case you might be able to get away with making that Customer details portion in my example, a Partial, and have it retrieve the data it needs Using Ajax after the client get's the response. But that's more up to you if that sort of thing even makes sense for your implementation.
Addendum:
It's worth noting that if you decide to try out ASP.NET MVC Core, ChildActions are no longer available. In which case your choices will be limited to partial views, ajax, or the newly introduced feature of Components. The last of which is similar to ChildActions, but slightly different in how they are implemented.
Perhaps an example will make this clearer.
Let's say you have a menu which appears on every page, so you put it in your layout. The menu will never change - there is just some basic navigation links, Home, About, Contact us etc, so you just use a normal partial view. This will work fine - as the content is static - you don't need to go to a database to get the data. You can just use #Html.Partial("Menu");.
Later you decide you need to change the menu so that it gets all the links from a database. You update your partial view to have a model that is a List<string> - one for each link.
Now, if you still want to just use a Partial View, every action would need to query the database to get the list of links, and every Model for every View would need to have a List<string> property for the links, so that it could pass this to the Menu Partial View. This would be a bad idea.
Instead, you would make a new Child Action GetMenuLinks() - this would query the database to get the links as a List<string>, and pass this to the Partial View. This puts the Child Action in charge of getting it's own data. This means you only need to have this query in one place, the 'About Us' action for example doesn't need to worry about getting the list of links for the menu.
Partial views
Use for sharing subsections of view markup between views. Partial views can
contain inline code, HTML helper methods, and references to other partial
views. Partial views do not invoke an action method, so they cannot be used
to perform business logic.
Child actions
Use for creating reusable UI controls or widgets that need to contain business
logic. When you use a child action, it invokes an action method, renders a
view, and injects the result into the response stream.
I use Html.Action() to load dynaimc content that I do not wish to contain in the view model (for instance, user information in a sidebar). It is very useful for keeping input and output view models identical.
Note that I always use Html.Action() in conjunction with applying the ChildActionOnlyAttribute to the controller method that I am calling so that the HTML fragment is not accessible via the URL.
Use Html.Partial when you require a subset of your view model to render the section in question--usually it is something that has to do with what you're working on. If could be a subsection of a form, a relevant content piece related to the main view etc. A partial receives its model information from the parent view.
Otherwise use Html.Action to render content that is independent of your main view, such as a navigation piece, an aside, or other distractions. Html.Action uses its own model provided by its controller, rather than provided by the parent view.
This question is answered (and elected for 149 times!) here:
Html.Partial vs Html.RenderPartial & Html.Action vs Html.RenderAction
Update
Sorry, meant to send you these postings rather
MVC Html.Partial or Html.Action\
#Html.Partial() Vs #Html.Action() - MVC Razor
Hope this helps.