In looking through samples I have seen a number of examples where it is possible to present data within a wpf applicaiton by binding to collections. However I was wondering is it possible to write to a collection from an applicaiton. Say for example i have 2 or more fields such as names and I wanted to have hte ability to add up to three names in my application ( all stored in memory). Will collections serve this purpose. In the past with asp.net I have done this by creating data tables and storing values on the fly or during the session. I am trying to learn WPF and I was wondering if collections work in the same fashion?
If so could you please post an example or point me to references that show examples of this?
Thank you in advance.
Use ObservableCollection as a datasource if you want UI to update on the changes you made to collection from your code.
See ObservableCollection<(Of <(T>)>) Class It also contains quite a good sample.
Related
I need to build our future business applications with WPF using MVVM.
My typical application consists of several windows/tab pages with grids and form style windows. Both edit windows and grid windows can be different depending on the logged in user, so most of them will be built datadriven.
And I'm trying to write as few code as possible, as not written code is the only one to be guaranteed error free .
So, now my question: how to structure the entire thing?
The View is clear to me - is is built using XAML or by code.
The ViewModel should contain the business logic and the validation rules and should let feed the View the data, and should contain the commands for the actions.
So, where to put the data? A select returns a DataTable. Should this datatable exposed through the ViewModel to the View for the grid windows?
And for the form windows? Should the single DataRow exposed trough the ViewModel to the View?
Are there other helper or intermediate classes needed?
Thank you for any useful suggestion!
Wolfgang
Its best way to go with WPF and MVVM,
I suggest before you start go thru the basics of MVVM. for your reference you can understand better here
The preferred UI paradigm in WPF is to have tab controls and grids in a single window, something like this:
You don't have to stop there, you can nest them as deeply as you need to for the sake of clarity.
I have bound a Data Grid to an ObservableCollection. It fills the grid with more than 200 records. Now user makes changes using editable control provided in the grid and finally clicks the save button to update the data back to database but I am not getting the idea how to update the modified collection back to the database because there is no PRIMARY KEY in the table.
The table has four columns apart from created by and modified by.
Like this i think i'll have to keep two collections. One older collection to compare against a new modified collection. I am quite new to think of better ideas.
What could be a simple and better approach?
You should refer to this video by Nikhil Kothari Developing with WCF Ria Services quickly and effectively.
There are several others on YouTube.
Hi i am trying to find the best way to manage the Data (that comes from tables in a Database) in your App.
My main question is, what is the best approach to take to then i successfully work with Bindings, Notifying Properties/Collections Changes?
My App is to manage the Inventory of all kind of things in an Enterprise, so i collect the Data to my App, and then i am using DataViews to store it? But this is the best approch to then i can work with bindings and Notifying Changes?
I am recently entering in WPF (about 2 months), the concept of ViewModel it's what i am trying to understand now, because seems that is the most thing used to manage the Data stored in an WPF App. Or maybe i am understanding all wrong.
What I am asking is for advices and examples to then i understand which is the best aprroach.
Note: In my case i have a Main Window with a DataGrid which have DataGridTextColumns and DataGridComboBoxColumns, and i have auxiliary Windows to manage Categories, Places and etc with ListViews.
Thanks in advance!
When we are talking about WPF, then of-course we are talking about MVVM pattern, its the best way :)
This link is the best start point for MVVM pattern:
MVVM for Beginners
I am using a WCF service reference in a WPF project, and my entity framework data model resides in WCF project.
And I am using MVVM Light framework. I am doing the following things:
I use LINQ in the service to get data and then fetch it from WPF, obersvablecollections usually.
Everything works in view part like populating datagrid, views as required.
But I have following doubts:
Is this correct way of transferring data between wcf and wpf.
I haven't used the Model for anything yet, I have doubt about when to use it?
I also wanted to save data from datagrid. I was able to pass on the observablecollection of updated data of datagrid to the service's function. But how do i update the entity from this collection? by looping? doesnt sound right. Once I update the entity from this collection I will be able to use saveChanges to update into database.
When I need to show hierarchal data in a treeview, where to make that data hierarichal, from stored procedure xml? use a view to create a grouping criteria column? create this column in service? create this column/property in presentation?
1 - There is no correct way, it depends on your requirements and goals.
2 - With MVVM, the model should sit between WPF and the database. That means all calls to the database should go through the model, and all writes to the database should also go through the model. The WPF GUI should only bind to the model. This usually means that your WPF portion consists mostly of XAML code. All code that accesses the database should be in the model.
There are good reasons for separating this.
You can write unit tests that on the model.
The view model is independent from the look of the GUI. This means that you can easily change the GUI by dropping in different components and just binding to the model.
A quick google search can probably yield more reasons.
3 - I would try to send over only the entities that have changed. This can be done by passing the collection to your view model, and have your view model figure out what has changed.
4 - I don't quite understand what you want to do. Usually, to make a TreeView, you should create HierarchicalDataTemplate for each of your view models. The TreeView control will take care of the rest. You should really do some tutorials on this one, because it's kinda hard to wrap your head around.
I have a service that returns an observable collection of persons that will be used to display the person name in a list box in my Silverlight application.
While designing the list box, the designer used sample data. However, when the xaml reaches the developer working on the view model and the service that returns an observable collection of persons to be displayed, there are some changes that need to be done.. like remove all bindings to the sample data, plug in the observable collection persons properties.
So my questions are:-
Is there a way to do this in a way where in design mode it shows the sample data and when it runs it shows the service data?
Is there a way for it to return service data while in design mode itself?
Does the designer using Expression Blend need to know what properties of the observable collection {persons} will be bound to the list box?
I would want to do this in an MVVM friendly manner {without using MVVM Light toolkit}.
Thanks for your time...
Loads of good examples out there:
http://blogs.msdn.com/b/avip/archive/2010/12/06/the-simplest-way-to-do-design-time-viewmodels-with-mvvm-and-blend.aspx
http://karlshifflett.wordpress.com/2009/10/28/ddesigninstance-ddesigndata-in-visual-studio-2010-beta2/
It's very simple. Lots of other resources on google if you need them
Edit based on comment
2. Is there a way for it to return service data while in design mode itself?
Possibly but I've not seen it. In my mind you probably wouldn't want to do this for many reasons.
You may get a delay before your data
shows up which could get quite
frustrating if you need to make a lot
of small changes.
You have a reliance on services being
available which is going to make you
even more unproductive if they ever
go down.
You or a designer doesn't have any
control over changing what is
displayed on an ad-hoc basis. At
least using the sample data system
you can change values to test
different scenarios without having to
get services data changed.
3. Does the designer using Expression Blend need to know what properties of the observable collection {persons} will be bound to the list box?
The designer/developer workflow is a tricky one. Obviously each project will be different, but having just finished a design heavy wpf project I can tell you that our designers want as little to do with Blend as possible.
The workflow that has worked for us, is for the developers (we have a front end team that work at the view/viewmodel level and backend team that build up the model and service layer) to build up the views as best they can. That means building the layout, composing the controls, adding most of the design and hooking up the bindings. We then had a designer who had experience in using Blend (there aren't many) delve in and tweak the designs to get them exactly as they wanted.
This way they had very little to do with the main brunt of the work and we could keep clean and organised views (something few designers would have the experience to do). The designers didn't really have to know anything about domain objects. It all worked very well once we'd worked out how it was going to work. Having the designers build up the views themselves would have been a nightmare in my opinion... and not something they'd have enjoyed either.