Question

I have Expander from WPF (and using Entity Framework 4 and MVVM pattern) which contains ContentControl bound to some inner ViewModel. All I want is to bind this content control LAZILY. That is I want my ViewModel to be “get” when the Expander is opened.

How to do that? How to make complex windows with inner ViewModels faster?

Answer 1

You could add an IsExpanded property to your ViewModel, bind the expander to it, and take the value of that property into account when returning the content of the ContentControl:

private bool _isExpanded;
public bool IsExpanded
{
    get { return _isExpanded; }
    set
    {
        _isExpanded = value;
        OnPropertyChange("IsExpanded");
        OnPropertyChange("Content");
    }
}

public SomeType Content
{
    get
    {
        if (!_isExpanded)
            return null;
        return LoadContent();
    }
}