CODEWITHSUNDEEP
c#wpfmvvm
Vishal
Vishal

Reputation: 6378

get value of a property from one viewmodel's current instance in another

I have a setup something like below:

MainWindow ------> MainWindowViewModel
  |--Menu
  |--Frame

Page1 --------> Page1ViewModel
Page2 --------> Page2ViewModel

Suppose my menu has 2 items in it namely Item1 and Item2. Menu's SelectedMenuItem is bound to a property called SelectedItem in MainWindowViewModel. When I click on Item1 I am navigated to Page1 and similarly when I click on Item2 I am navigated to Page2.

Now, In Page1ViewModel and in Page2ViewModel I want to have the current value of SelectedItem. How can I get that value ?

Before asking this question I have looked at Mediator Pattern as well as EventAggregator but for a newbie(in WPF) like me it is very hard to understand those patterns. Is there any other solutions that I can adopt?

Also I have looked at the accepted answer of this question. I have tried the code given there but I don't get value in Page1ViewModel or Page2ViewModel.

Update ---> @Poke

Sorry, I didn't mentioned that in question.

I have another item in my menu called Item3. When I Click on it Page1 should be visible.

So, now my setup is:

MenuItem   |      Page     |    ViewModel
-----------+---------------+-------------
Item1      |     Page1     |  Page1ViewModel
Item2      |     Page2     |  Page2ViewModel
Item3      |     Page1     |  Page1ViewModel

The only difference between Item1 Click and Item3 Click is that :

  1. When Clicking on Item1 :

    A Combobox called cbEffects should be visible.

  2. When Clicking on Item1 :

    A Combobox called cbEffects should be hidden.

Upvotes: 2

Views: 2045

Answers (2)

JGU
JGU

Reputation: 909

Not sure if this is what you are looking for, but you can access the application viewmodel through the App.Current.MainWindow.DataContext property, and store common properties in there.. or, what I do, is store variables accessible to all views in a static class..

Upvotes: 0

Brock Hensley
Brock Hensley

Reputation: 3655

Here's one example of maintaining ViewModel instances in a static property available anywhere in your application via SessionViewModel.GetModuleInstance('VMName'):

namespace MyProject.ViewModels
{
    public sealed class SessionViewModel : ViewModelBase
    {
        private static readonly SessionViewModel instance = new SessionViewModel();
        public static SessionViewModel Instance
        {
            get { return instance; }
        }

        private List<IModule> modulesOpen;
        public List<IModule> ModulesOpen
        {
            get { return modulesOpen; }
            set
            {
                modulesOpen = value;
                NotifyPropertyChanged(() => ModulesOpen);
            }
        }
    }

    public static IModule GetModuleInstance(string moduleName)
    {
        string finalName = "MyProject.ViewModels." + moduleName + "ViewModel";
        IModule moduleToOpen = null;
        if (Instance.ModulesOpen != null)
        {
            moduleToOpen = Instance.ModulesOpen.SingleOrDefault(mod => mod.ModuleName == moduleName);
        }
        else
        {
            Instance.ModulesOpen = new List<IModule>();
        }
        if (moduleToOpen != null) return moduleToOpen;
        Type module = Type.GetType(finalName);
        moduleToOpen = (IModule) Activator.CreateInstance(module);
        Instance.ModulesOpen.Add(moduleToOpen);
        return moduleToOpen;
    }

    public class UsageExample()
    {
        var vm = SessionViewModel.GetModuleInstance("MyVMName");
        ((MyVMName)vm).MyVMPropertyName;
    }
}

Upvotes: 1

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