I'm creating an application that enables a user to insert, update and delete data that has been entered and then shown in a data-grid (CRUD operations).
In my View Model, it contains properties which are bound to the xaml (Firstname
for example). It also contains a navigation property as well as validation attributes.
[Required(ErrorMessage = "First Name is a required field")]
[RegularExpression(@"^[a-zA-Z''-'\s]{1,20}$", ErrorMessage = "First Name must contain no more then 20 characters and contain no digits.")]
public string FirstName
{
get { return _FirstName; }
set
{
if (_FirstName == value)
return;
_FirstName = value;
OnPropertyChanged("FirstName");
}
}
Furthermore, it contains commands for the xaml
to execute, which creates an instance of the CRUD operation;
private void UpdateFormExecute()
{
var org = new OrganisationTypeDetail();
UpdateOrganisationTypeDetail(org);
}
And lastly, it contains the CRUD operations as well. Such as the Insert, Update and Delete.
Which leads me to my question. if I want to implement the correct MVVM way, is all this code too much for the view model to contain?
Should I use the model and create a collection within my View-model and bound that to my xaml
? Would this be the correct way of doing it?
Should I use a Repository system for the CRUD operations? If so, how would I pass the data from the text fields through to the model to get updated?
Im new to WPF, MVVM and finding it hard to adapt without proper guidance.
Model-View-ViewModel (MVVM) is a structural design pattern that separates objects into three distinct groups: Models hold application data. They're usually structs or simple classes. Views display visual elements and controls on the screen.
Model–view–viewmodel (MVVM) is a software architectural pattern that facilitates the separation of the development of the graphical user interface (the view) – be it via a markup language or GUI code – from the development of the business logic or back-end logic (the model) so that the view is not dependent on any ...
MVVM is better than MVC/MVP because of its unidirectional data and dependency flow. Dependency is one way, thus it is a lot easier to decouple it when we need to. It is also easier for testing.
I would say that this is a correct way to implement MVVM, but not the correct way to implement MVVM.
What I mean by this is that there is no one correct way to implement this pattern. if you have created a ViewModel that can be bound to your View, without having any extra logic within your View (i.e. code-behind) then you have captured the essence of MVVM.
Whether or not you add more patterns and structure to your code is entirely up to you. If this is a simple application, I would keep the patterns light. Go ahead and have your ViewModel talk directly with a repository. You current code looks just fine to me in that respect.
If this is a large application, you might want to add further layers, like a service layer, data access layer. You might want to think about dependency injection.
But don't just adopt a pattern, or add an extra layer just because you think you should. Dependency Injection sounds cool, but in many cases it is more hassle than it is worth!
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