Question

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.

Answer 1

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!