MRT to MRT Core migration
This topic contains guidance for migrating from UWP's Resource Management System (also known as MRT) to the Windows App SDK's MRT Core.
MRT Core is a streamlined version of MRT. For more info, see Manage resources with MRT Core.
Summary of API and/or feature differences
For ease of migration, MRT Core APIs are very similar to MRT APIs. For API reference documentation, see the Microsoft.Windows.ApplicationModel.Resources namespace.
Note
Not all of the MRT APIs exist in MRT Core. But all of the APIs necessary for the basic functionality of MRT are included.
Change namespace
In UWP, the MRT APIs are in the Windows.ApplicationModel.Resources.Core namespace. In the Windows App SDK, the MRT Core APIs are in the Microsoft.Windows.ApplicationModel.Resources namespace. So you'll need to change that namespace name in your source code (add Microsoft. at the start, and remove the .Core at the end).
Note
In Windows App SDK 1.0 Preview 1 and later releases, MRT Core APIs are in the Microsoft.Windows.ApplicationModel.Resources namespace. In releases earlier than that, they are in the Microsoft.ApplicationModel.Resources namespace.
ResourceManager class
This section applies if you're using the Windows.ApplicationModel.Resources.Core.ResourceManager.Current property in your UWP app.
// In a UWP app
using Windows.ApplicationModel.Resources.Core;
...
var currentResourceManager = ResourceManager.Current;
// In a UWP app
#include <winrt/Windows.ApplicationModel.Resources.Core.h>
using namespace winrt::Windows::ApplicationModel::Resources::Core;
...
auto currentResourceManager{ ResourceManager::Current() };
Instead, in your Windows App SDK app, create a new Microsoft.Windows.ApplicationModel.Resources.ResourceManager.
// In a Windows App SDK app
using Microsoft.Windows.ApplicationModel.Resources;
...
var currentResourceManager = new ResourceManager();
// In a Windows App SDK app
#include <winrt/Microsoft.Windows.ApplicationModel.Resources.h>
using namespace winrt::Microsoft::Windows::ApplicationModel::Resources;
...
ResourceManager currentResourceManager;
ResourceContext.GetForCurrentView, and ResourceContext.GetForViewIndependentUse
UWP's MRT ResourceContext class distinguishes between a ResourceContext for the current view, and one for view-independent use.
For the Windows App SDK's MRT Core ResourceContext class, your app needs to determine the correct context (resource qualifier values), and the concepts of current view and view-independent use no longer apply.
- So if you're using the ResourceContext.GetForCurrentView API or the ResourceContext.GetForViewIndependentUse API, then use ResourceManager.CreateResourceContext instead.
Resource qualifier values
In UWP's MRT, the resource context qualifier values are determined for the app. While in MRT Core, only the language value is populated. Your app needs to determine other values for itself. Here's an example, where it's assumed your XAML view contains an element named layoutRoot.
// In a Windows App SDK app
using Microsoft.Windows.ApplicationModel.Resources;
...
var currentResourceManager = new ResourceManager();
var resourceContext = currentResourceManager.CreateResourceContext();
int scaleFactor = Convert.ToInt32(layoutRoot.XamlRoot.RasterizationScale * 100);
resourceContext.QualifierValues[KnownResourceQualifierName.Scale] = scaleFactor.ToString();
string s = resourceContext.QualifierValues[KnownResourceQualifierName.Scale];
// In a Windows App SDK app
#include <winrt/Microsoft.Windows.ApplicationModel.Resources.h>
using namespace winrt::Microsoft::Windows::ApplicationModel::Resources;
...
ResourceManager currentResourceManager;
auto resourceContext{ currentResourceManager.CreateResourceContext() };
auto scaleFactor{ layoutRoot().XamlRoot().RasterizationScale() * 100 };
resourceContext.QualifierValues().Insert(L"Scale", std::to_wstring((int)scaleFactor));
auto s{ resourceContext.QualifierValues().Lookup(L"Scale") };
Resource qualifier value change
UWP's MRT provides the ResourceQualifierObservableMap.MapChanged event. And this section applies if your UWP app is handling that event in order to listen to qualifier value changes.
MRT Core doesn't provide any notification mechanics around environment changes. So your Windows App SDK app needs to detect such changes on its own if you wish to update resources based on environment changes.
An MRT Core sample app
Also see the Load resources using MRT Core sample app project, which demonstrates how to use the MRT Core API surface.
