Setup Windows Projects

Adding new Windows projects to an existing Xamarin.Forms solution

Older Xamarin.Forms solutions (or those created on macOS) will not have Universal Windows Platform (UWP) app projects. Therefore, you'll need to manually add a UWP project to build a Windows 10 (UWP) app.

Add a Universal Windows Platform app

Visual Studio 2019 on Windows 10 is recommended to build UWP apps. For more information about the Universal Windows Platform, see Intro to the Universal Windows Platform.

UWP is available in Xamarin.Forms 2.1 and later, and Xamarin.Forms.Maps is supported in Xamarin.Forms 2.2 and later.

Check the troubleshooting section for helpful tips.

Follow these instructions to add a UWP app that will run on Windows 10 phones, tablets, and desktops:

1 . Right-click on the solution and select Add > New Project... and add a Blank App (Universal Windows) project:

2 . In the New Universal Windows Platform Project dialog, select the minimum and target versions of Windows 10 that the app will run on:

3 . Right-click on the UWP project and select Manage NuGet Packages... and add the Xamarin.Forms package. Ensure the other projects in the solution are also updated to the same version of the Xamarin.Forms package.

4 . Make sure the new UWP project will be built in the Build > Configuration Manager window (this probably won't have happened by default). Tick the Build and Deploy boxes for the Universal project:

5 . Right-click on the project and select Add > Reference and create a reference to the Xamarin.Forms application project (.NET Standard or Shared Project).

6 . In the UWP project, edit App.xaml.cs to include the Init method call inside the OnLaunched method around line 52:

// under this line
rootFrame.NavigationFailed += OnNavigationFailed;
// add this line
Xamarin.Forms.Forms.Init (e); // requires the `e` parameter

7 . In the UWP project, edit MainPage.xaml by removing the Grid contained within the Page element.

8 . In MainPage.xaml, add a new xmlns entry for Xamarin.Forms.Platform.UWP:

xmlns:forms="using:Xamarin.Forms.Platform.UWP"

9 . In MainPage.xaml, change the root <Page element to <forms:WindowsPage:

<forms:WindowsPage
...
   xmlns:forms="using:Xamarin.Forms.Platform.UWP"
...
</forms:WindowsPage>

10 . In the UWP project, edit MainPage.xaml.cs to remove the : Page inheritance specifier for the class name (since it will now inherit from WindowsPage due to the change made in the previous step):

public sealed partial class MainPage  // REMOVE ": Page"

11 . In MainPage.xaml.cs, add the LoadApplication call in the MainPage constructor to start the Xamarin.Forms app:

// below this existing line
this.InitializeComponent();
// add this line
LoadApplication(new YOUR_NAMESPACE.App());

Note

The argument to the LoadApplication method is the Xamarin.Forms.Application instance defined in your .NET standard project.

12 . Add any local resources (eg. image files) from the existing platform projects that are required.

Troubleshooting

"Target Invocation Exception" when using "Compile with .NET Native tool chain"

If your UWP app is referencing multiple assemblies (for example third party control libraries, or your app itself is split into multiple libraries), Xamarin.Forms may be unable to load objects from those assemblies (such as custom renderers).

This might occur when using the Compile with .NET Native tool chain which is an option for UWP apps in the Properties > Build > General window for the project.

You can fix this by using a UWP-specific overload of the Forms.Init call in App.xaml.cs as shown in the code below (you should replace ClassInOtherAssembly with an actual class your code references):

// You'll need to add `using System.Reflection;`
List<Assembly> assembliesToInclude = new List<Assembly>();

// Now, add in all the assemblies your app uses
assembliesToInclude.Add(typeof (ClassInOtherAssembly).GetTypeInfo().Assembly);

// Also do this for all your other 3rd party libraries
Xamarin.Forms.Forms.Init(e, assembliesToInclude);
// replaces Xamarin.Forms.Forms.Init(e);

Add an entry for each assembly that you have added as a reference in the Solution Explorer, either via a direct reference or a NuGet.

Dependency Services and .NET Native Compilation

Release builds using .NET Native compilation can fail to resolve dependency services that are defined outside the main app executable (such as in a separate project or library).

Use the DependencyService.Register<T>() method to manually register dependency service classes. Based on the example above, add the register method like this:

Xamarin.Forms.Forms.Init(e, assembliesToInclude);
Xamarin.Forms.DependencyService.Register<ClassInOtherAssembly>(); // add this