CODEWITHSUNDEEP
c#asynchronousmvvmwindows-phone-8.1
sidy3d
sidy3d

Reputation: 549

Mvvm application loading data

I have a windows phone application built using the MVVM pattern and I have pages that have to load data. I know this practice is bad but I used an async void LoadData() called in the constructor to load data. Are there any better ways to achive this?

Thanks in advance

public class SomeViewModel: BaseViewModel
{
    public SomeViewModel()
    {
        LoadData();   
    }

    public async void LoadData()
    {
        //load data, ex. add items to list
    }

    private RelayCommand _refreshCommand;
    /// <summary>
    /// Gets the RefreshCommand.
    /// </summary>
    public RelayCommand RefreshCommand
    {
        get
        {
            return _refreshCommand
                ?? (_refreshCommand = new RelayCommand(() => LoadData()));
        }
    }
}

Upvotes: 0

Views: 277

Answers (1)

Breno Santos
Breno Santos

Reputation: 110

Who's responsible for create view model is Ioc in Locator, so putting your LoadData method on constructor you will not have control.

My advice: Does not load data in Vm constructor. Do like this:

public class SomeViewModel: BaseViewModel
{

    public IMessenger Messenger { get { return base.MessengerInstance; } }

    public SomeViewModel()
    {
        Initialize(); 
    }

    public void Initialize()
    {
        RegisterMessengers();
    }

    public void RegisterMessengers()
    {
         Messenger.Register<string>(
            this, "TokenRefresh", u => LoadData(u));
    }

    public async void LoadData(string u)
    {
        //load data, ex. add items to list
    }

    private RelayCommand _refreshCommand;
    /// <summary>
    /// Gets the RefreshCommand.
    /// </summary>
    public RelayCommand RefreshCommand
    {
        get
        {
            return _refreshCommand
                ?? (_refreshCommand = new RelayCommand(() => LoadData()));
        }
    }
}

And you call from another view model like that:

_navigationService.Navigate(typeof(YourView));
Messenger.Send("", "TokenRefresh");

Upvotes: 1

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