How to work with windows in WPF/MVVM?

Question

.NET

Hello.
How to properly implement windows in WPF/MVVM? For example, the main form for entering login / passwords opens, after entering data, another form opens, depending on which user and what role he has. I googled and didn't find any suitable examples. Everywhere modal windows are considered. Leave examples, please. Which are made strictly in accordance with the MVVM pattern. Thanks to.

Answer 1

Good afternoon.
Here is an old article with three different implementations of showing child windows. Now I'm actually using a different approach. When all child Views are created as controls. The child window is one and contains a ContentPresenter. When a child window's show method is called, a ViewModel is placed in its DataContext. And how to match View and ViewModel stored in resources:

<DataTemplate DataType="{x:Type viewmodel:ResponsePart8ViewModel}">
     <view:ResponsePart8View HorizontalAlignment="Stretch" />
</DataTemplate>

When showing a window, the ContentPresenter itself, by the type of the object lying in the DataContext, creates a View. If it is not very clear, then I can throw off a detailed example.

Answer 2

there are no navigation conventions in the MVVM pattern. The topic itself is complex, I recommend to see how it is
done in
Prism which shows the necessary View according to the transferred VM, stores the backstack, etc.

Answer 3

I don't see a problem, to be honest. If the view model is initialized in all windows in the same way, especially if automatically, then you can simply create windows and show them. Different depending on the conditions.
Example:
Model:

namespace MyApp.MyNamespace.ViewModels
{
  public class MyWindowModel : INotifyPropertyChanged
  {
     private object _foo;
     public object Foo
     {
      get { return _foo; }
      set { _foo = value; RaisePropertyChanged("Foo"); }
     }

  ...

  }
}

View:

<Window x:Class="MyApp.MyNamespace.MyWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:viewModels="clr-namespace:MyApp.MyNamespace.ViewModels">
   <Window.DataContext>
      <viewModels:MyWindowModel x:Key="Model" />
   </Window.DataContext>
   <Grid>
      <TextBlock Text={Binding Foo} />
   </Grid>
</Window>

You can call it like this, for example, as you say from the login window:

...
// проверяем успешность логина
if (!loginSuccess)
  return;

// если всё хорошо, то создаём новое окно
var myWindow = new MyWindow();

// если нужно - что-то делаем с моделью внутри окна
var model = myWindow.DataContext as MyWindowModel;
model.Foo = new object();

// показываем новое окно
myWindow.Show();

// закрываем текущее окно логина
var window = Application.Current.Windows[0];
if (window != null)
  window.Close();

Answer 4

So it's not difficult.
On the button you hang a command with logic and a transition to the desired page.
I can throw off the simplest example with Prism, but for UWP.