CODEWITHSUNDEEP
c#mvvmviewmodelcommunication
Rudi
Rudi

Reputation: 936

Call method of a ViewModel from MainViewModel

I'm currentyl having a problem by communicating between 2 ViewModels. Download my app here to see the problem: http://www76.zippyshare.com/v/26081324/file.html

I have 2 views.

The MainView has a ContentControl with the Content = FirstView. My FirstViewModel looked something like this:

public class FirstViewModel : ViewModelBase
{

    public FirstViewModel()
        {
        One = "0";
        Two = "0";
        Ergebnis = 0;
    }
    private string _one;
    public string One
    {
        get { return _one; }
        set
        {
            if (value != null)
            {
                    _one = value;
                    Calculate();
                    RaisePropertyChanged(() => One);
            }
        }
    }

    private string _two;
    public string Two
    {
        get { return _two; }
        set
        {
                    _two = value;
                    Calculate();
                    RaisePropertyChanged(() => Two9;
        }

    }

    private decimal _ergebnis;
    public decimal Ergebnis
    {
        get { return _ergebnis; }
        set
        {
            if (value != null)
            {
                if (value != _ergebnis)
                {
                    _ergebnis = value;
                    RaisePropertyChanged(() => Ergebnis);
                }
            }


        }
    }

    public void Calculate()
    {
        if (Two != null)
        {
            for (int i = 0; i < 500; i++)
            {
                Ergebnis = i;
            }
            Ergebnis = (decimal.Parse(One) + decimal.Parse(Two));
        }
    }

As you can see, every time the value of the property 'One' or 'Two' is being changed, it'll call Calculate(). What I want now is that when I click on a button in the MainView, the MainViewModel has to call Calculate() in FirstViewModel. So I commented out the Calculate() in the propertys and implemented a RelayCommand in my MainViewModel:

Button in MainView

<Button Grid.Row="3" Command="{Binding ChangeValue}" />

MainViewModel 

public MainViewModel
{
    ChangeValue = new RelayCommand(ChangeValueCommandExecute);
}

public RelayCommand ChangeValue { get; private set; }
private FirstViewModel fwm;

private void ChangeValueCommandExecute()
{
    //CurrentView = Content of the ContentControl in the MainView, which is FirstView
    if (CurrentView.Content.ToString().Contains("FirstView"))
    {   
        fwm.Calculate();
    }
}

This means when I click on the Button, ChangeValueCommandExecute() is being called. The Command will call fwm.Calculate() and set the new sum (=Ergebnis). The problem is that when Calculate() is being called, the value of 'One' and 'Two' is always "0". So how do I call a method of a ViewModel in another ViewModel?

Edit: To make it clear: I want to call the method 'Calculate()' of FirstViewModel() without using 'new FirstViewModel()'!

Upvotes: 3

Views: 1347

Answers (1)

ChrisO
ChrisO

Reputation: 5465

I can't view your project because it requires Windows 8 but are you sure the FirstViewModel you have as the DataContext of your FirstView is the same FirstViewModel you're referring to in your MainViewModel? From what I can see, you're newing up a FirstViewModel in the constructor of the MainViewModel which is private.

Upvotes: 2

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