Binding for WPF Styles

Question

I\'m trying to create a custom control - a button - which will have multiple styles applied to it depending on the value of a property within the data context.

What

Answer 1

For those of us who can't use multi value converter (I'm looking at you SL4 and WP7:), thanks to Steven's answer I found a way using an ordinary value converter.

The only assumption is the style value is contained within the property of the style being set.

So if you're using the MVVM pattern then the style value (such as TextSmall, TextMedium, TextLarge) is assumed to be part of the view model, and all you have to do is pass the converter parameter defining the name of style.

For example, say your view model has property:

public string ProjectNameStyle
{
    get { return string.Format("ProjectNameStyle{0}", _displaySize.ToString()); }
}

Application style:

XAML view:

With your StyleConverter class implementing IValueConverter:

public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
    if (targetType != typeof(Style))
    {
        throw new InvalidOperationException("The target must be a Style");
    }

    var styleProperty = parameter as string;
    if (value == null || styleProperty == null)
    {
        return null;
    }

    string styleValue = value.GetType()
        .GetProperty(styleProperty)
        .GetValue(value, null)
        .ToString();
    if (styleValue == null)
    {
        return null;
    }

    Style newStyle = (Style)Application.Current.TryFindResource(styleValue);
    return newStyle;
}

Note that this is WPF code, as the converter is derived from a MarkupExtension as well as IValueConverter, but it will work in SL4 and WP7 if you use static resource and add a bit more leg work as the TryFindResource method doesn't exist.

Hope that helps someone, and thanks again Steven!