Defining a ResourceDictionary only once

Question

i have the following ResourceDictonary

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    xmlns:SharedHelpers="clr-namespace:Shared.Helpers;assembly=Shared"
                    xmlns:SharedViewModels ="clr-namespace:Shared.ViewModels;assembly=Shared"
                    xmlns:SharedViews="clr-namespace:Shared.Views;assembly=Shared"
                    >

<DataTemplate DataType="{x:Type SharedViewModels:DatabaseViewModel}">
   <SharedViews:DatabaseView/>
</DataTemplate>

<DataTemplate DataType="{x:Type SharedViewModels:ProxyViewModel}">
  <SharedViews:ProxiesView/>
</DataTemplate>

<DataTemplate DataType="{x:Type SharedViewModels:AppUserViewModel}">
   <SharedViews:AppUserView/>
</DataTemplate>
<!--ViewModels-->
<SharedViewModels:DatabaseViewModel x:Key="DatabaseViewModel"/>
<SharedViewModels:AppUserViewModel x:Key="AppUserViewModel"/>
<SharedViewModels:ProxyViewModel x:Key="ProxyViewModel"/>
</ResourceDictionary>

as you can see those resource are static and i want to access them from my other libraries and classes so what i did is in my App.xaml i did define the dictionary as the following

 <Application.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <ResourceDictionary x:Name="dict"  Source="ResourceDict.xaml"/>
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </Application.Resources>

from my code behind i need to access the instances in this dictionary without having to redefine it, so i found

var databaseViewModelInstance = Application.Current.Resources.MergedDictionaries["dict"]["DatabaseViewModel"] as Shared.ViewModels.DatabaseViewModel;

but the problem is it allows me to access the dictionary only by index and not by its name, how can i access the dictionary by its name without having to define a new resource dictionary instance in every class that i want to access it from?

the following works just fine

var databaseViewModelInstance = Application.Current.Resources.MergedDictionaries[0]["DatabaseViewModel"] as Shared.ViewModels.DatabaseViewModel;

Answer 1

Accessing a resource dictionary by name is a bit problematic since it doesn't derive from FrameworkElement and thus doesn't have a Name property. If it had, you could do the following:

Application.Current.Resources.MergedDictionaries
                             .First(x => x.Name == "dict")["DatabaseViewModel"] as Shared.ViewModels.DatabaseViewModel;

However, instead of filtering by name, you can filter by source:

Application.Current.Resources.MergedDictionaries
                             .First(x => x.Source.OriginalString == "ResourceDict.xaml")["DatabaseViewModel"] as Shared.ViewModels.DatabaseViewModel;

Answer 2

I'm not sure if you can get a ResourceDictionary from a MergedDictionaries collection by name. However, it looks as though you only want to access it to get a particular resource within it (makes sense).

In this case, you may want to think about using FrameworkElement.TryFindResource.

This should search up the logical tree and arrive at your App.xaml level eventually. For clarity, you should be able to get your DatabaseViewModel by

FrameworkElement fe = new FrameworkElement();
var myResource = fe.TryFindResource("DatabaseViewModel");