C# 4 and .NET 4

1006 ❘ ChaPTer 35 cOre wpf
accessing resources from Code
To access resources from code - behind, the base class FrameworkElement implements the method
FindResource() , so you can invoke the FindResource() method with every WPF object.
To do this, button1 doesn ’ t have a background specifi ed, but the Click event is assigned to the method
button1_Click :
< Button Name="button1" Width="220" Height="50" Margin="5" Click="button1_Click" >
Apply Resource Programmatically
< /Button >
code snippet StylesAndResources/ResourceDemo.xaml
With the implementation of button1_Click() , the FindResource() method is used on the Button that
was clicked. Then a search for the resource MyGradientBrush happens hierarchically, and the brush is
applied to the Background property of the control. The resource MyGradientBrush was created previously
in the resources of the StackPanel :
public void button1_Click(object sender, RoutedEventArgs e)
{
Control ctrl = sender as Control;
ctrl.Background = ctrl.FindResource("MyGradientBrush") as Brush;
}
code snippet StylesAndResources/ResourceDemo.xaml .cs
If FindResource() does not find the resource key, then an exception is thrown. If
you don’t know for sure if the resource is available, then you can use the method
TryFindResource() instead. TryFindResource() returns null if the resource is not
found.
dynamic resources
With the StaticResource markup extension, resources are searched at load time. If the resource changes
while the program is running, then you should use the DynamicResource markup extension instead.
The next example is using the same resource as defi ned previously. The earlier example used
StaticResource . This button uses DynamicResource with the DynamicResource markup extension. The
event handler of this button changes the resource programmatically. The handler method button2_Click is
assigned to the Click event handler:
< Button Name="button2" Width="200" Height="50" Foreground="White" Margin="5"
Background="{DynamicResource MyGradientBrush}" Content="Change Resource"
Click="button2_Click" / >
code snippet StylesAndResources/ResourceDemo.xaml
The implementation of button2_Click() clears the resources of the StackPanel and adds a new resource
with the same name, MyGradientBrush . This new resource is very similar to the resource that is defi ned in
XAML code; it just defi nes different colors:
private void button2_Click(object sender, RoutedEventArgs e)
{
myContainer.Resources.Clear();
var brush = new LinearGradientBrush
{
StartPoint = new Point(0, 0),
EndPoint = new Point(0, 1)
};
brush.GradientStops = new GradientStopCollection()
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