Daniel Hoelbling-Inzko talks about programming

Displaying different screens with ContentPresenters in Silverlight

In WPF you can use a ContentPresenter with DataTemplate to display different Views for different ViewModels. And although writing those DataTemplates gets old pretty quickly (and you resort to frameworks or roll your own code to alleviate that problem), I do like to use them in small demo apps at times.

Silverlight does not support DataTemplates with types on them, so you can’t use ContentPresenters like you would in WPF.

But in this case it helps to understand what a DataTemplate is doing in WPF to easily replicate that behavior in Silverlight. DataTemplates (in this case) are little more than Converters that take objects and supply a template that is then used to display that object to the screen.

Once you know that, it gets rather simple: Simply implement IValueConverter and return a Silverlight UserControl in the Convert method.

You can even write something as simple as this:

public class ViewConverter : IValueConverter
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        if (value.GetType() == typeof(NewCustomerViewModel))
            return new NewCustomer();
        if (value.GetType() == typeof(CustomerListViewModel))
            return new MasterDetail();
        return null;

public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) { throw new NotImplementedException(); } }

Once your Converter can translate ViewModels (or any object) into Views you can then bind your ContentPresenter to use that Converter:

<ContentPresenter Content="{Binding ActiveScreen, Converter={StaticResource ViewConverter}}" />

You would obviously not want to use the code above, but rather hook your ViewConverter into your Inversion of Control container or something similar (or just use Caliburn.Micro).

There are a number of UI frameworks out there that make writing complex MVVM applications a lot easier. Caliburn, Caliburn.Micro and Prism. I tried some of them and I really liked them, but I found that you should really learn how Silverlight/WPF works before you resort to these Frameworks, as most of their features only start making sense once you start understanding the problems those frameworks set out to solve.

Filed under net, programmierung, wpf

My Photography business


dynamic css for .NET