Accessing a resource via codebehind in WPF

Question

I have a custom collection defined in my window resources as follows (in a Sketchflow app so the window is actually a UserControl):

<UserControl.Resources>
    <ds:MyCollection x:Key="myKey" x:Name="myName" />
</UserControl.Resources>

I want to be able to refer to this collection in the codebehind, which I expected would be by the x:Name, but I can't seem to access it.

I can get a reference to it using

myRef = (MyCollection) this.FindName("myKey");

but this seems hackish. Is this bad practice, and what would be better? Thanks :)

Stringpiece

Answer 1

You should use System.Windows.Controls.UserControl's FindResource() or TryFindResource() methods.

Also, a good practice is to create a string constant which maps the name of your key in the resource dictionary (so that you can change it at only one place).

Tl

You can use: Application.Current.FindResource(errorColorResourceName) as MyCollection or this.FindResource("RainbowBrush") as MyCollection. It depends on the context. – Roughen

Can you elaborate on "Also, a good practice is to create a string constant which maps the name of your key in the resource dictionary (so that you can change it at only one place)." ? Where would such a string constant go that would change the XAML key as well as the C# code behind? – Vagus

+1 for > Can you elaborate on "Also, a good practice is to create a string constant which maps the name of your key in the resource dictionary (so that you can change it at only one place)." ? Where would such a string constant go that would change the XAML key as well as the C# code behind? – Vidicon

@MikeChristiansen AdonisUI is a good exemple of that, if you look in src/AdonisUI/Brushes.cs you have a bunch of keys that are used in the templates, for example in Buttons.cs where you have a {DynamicResource {x:Static adonisUi:Brushes.ForegroundBrush}}. – Gallman

Answer 2

You may also use this.Resources["mykey"]. I guess that is not much better than your own suggestion.

Chamois

This is for Windows 8 Store Apps. – Vauntcourier

@cederlof, you can use this with WPF too. – Enenstein

This will not work if the resource is in another file, for instance a theme color. FindResource is the way to go. – Fridlund

Answer 3

Not exactly direct answer, but strongly related:

In case the resources are in a different file - for example ResourceDictionary.xaml

You can simply add x:Class to it:

<ResourceDictionary x:Class="Namespace.NewClassName"
                    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" >
    <ds:MyCollection x:Key="myKey" x:Name="myName" />
</ResourceDictionary>

And then use it in code behind:

var res = new Namespace.NewClassName();
var col = res["myKey"];

Uncork

+1, but to be able to find resources using it's key I had to call res.InitializeComponent() before attempting to access the key otherwise the object would show no keys and the call to res["myKey"] would return null. – Sneaker

Wow that's awesome... I never knew you could do that and it just solved a problem for me quick and easy! I did need to call InitializeComponent() like @StephenRoss said but other than that works like a charm. – Phylloid

A perfect solution to use from Converters – Tussock

Answer 4

If you want to access a resource from some other class (i.g. not a xaml codebehind), you can use

Application.Current.Resources["resourceName"];

from System.Windows namespace.

Ginger

This is useful if you need to access the resource from a static constructor or method, and therefore don't have the ability to call FindResource or TryFindResource. – Incisure

Answer 5

You can use a resource key like this:

<UserControl.Resources>
    <SolidColorBrush x:Key="{x:Static local:Foo.MyKey}">Blue</SolidColorBrush>
</UserControl.Resources>
<Grid Background="{StaticResource {x:Static local:Foo.MyKey}}" />

public partial class Foo : UserControl
{
    public Foo()
    {
        InitializeComponent();
        var brush = (SolidColorBrush)FindResource(MyKey);
    }

    public static ResourceKey MyKey { get; } = CreateResourceKey();

    private static ComponentResourceKey CreateResourceKey([CallerMemberName] string caller = null)
    {
        return new ComponentResourceKey(typeof(Foo), caller); ;
    }
}

Incus

Note that this depends on the type of key. E.g. a key in a DataTemplate is of type DataTemplateKey. – Alibi

Answer 6

I got the resources on C# (Desktop WPF W/ .NET Framework 4.8) using the code below

{DefaultNamespace}.Properties.Resources.{ResourceName}

Cultivar

Answer 7

A nice clean example from Microsoft documents makes it simple:

private void myButton_Click(object sender, RoutedEventArgs e)
{
  Button button = (Button)sender;
  button.Background = (Brush)this.FindResource("RainbowBrush");
}

Macule

This has already been answered. – Acrylonitrile