Adjust an Uno Solution for a faster build with Visual Studio 2022

The Uno Platform template provides a cross-targeted Class library that includes multiple target frameworks. While building with the command line dotnet build -f net7.0-ios only builds the application's head and the class library for net7.0-ios, Visual Studio builds all the target frameworks, regardless of the project head's target framework.

Considering that during development, it is common to work on a single platform at a given time, here's a suggested set of modifications that can be performed on the solution to restrict the active build platform:

1. Let's create a set of solution filters to ensure that individual project heads can be loaded:

   1. Create a new app template with iOS, Android, WebAssembly and Windows targets selected.
   2. Right click on the .Mobile and .Wasm projects and select Unload Project
   3. On the top level Solution node, right-click to select Save As Solution Filter, name the filter MyApp-Windows-Only.slnf
   4. Right-click on the Mobile project, select Reload Project
   5. Unload the .Windows project, then save a new solution filter called MyApp-Mobile-Only.slnf
   6. Repeat the operation with the .Wasm project, with a solution filter called MyApp-Wasm-Only.slnf

   These solution filters will prevent Visual Studio to restore NuGet packages for TargetFrameworks that will be ignored by the configuration done below.

2. Now, next to the solution file, create a file named targetframework-override.props:

   <Project>
       <Import Project="solution-config.props" Condition="exists('solution-config.props')" />
   
       <!-- Override the TargetFrameworks list with the one specified in MyAppTargetFrameworkOverride -->
       <PropertyGroup Condition="'$(MyAppTargetFrameworkOverride)'!=''">
           <TargetFrameworks>$(MyAppTargetFrameworkOverride)</TargetFrameworks>
       </PropertyGroup>
   </Project>
   

3. Also next to the solution file, create a file named solution-config.props.sample:

   <Project>
       <PropertyGroup>
           <!--
           Uncomment the following line to enable single-target framework builds
           in order to get faster performance when debugging for a single platform.
   
           Once this file is modified, use the appropriate solution filter to avoid
           NuGet restore issues.
   
           Available target frameworks can be found in the project heads of your solution.
           -->
           <!-- <MyAppTargetFrameworkOverride>net7.0-ios</MyAppTargetFrameworkOverride> -->
       </PropertyGroup>
   </Project>
   

4. Next, in all projects of the solution which are cross-targeted (with multiple TargetFrameworks values), add the following lines right after the PropertyGroup which defines <TargetFrameworks>:

   <!-- Import the TargetFramework override configuration -->
   <Import Project="../../targetframework-override.props" />
   

   The file should then look like this:

   <Project Sdk="Microsoft.NET.Sdk">
       <PropertyGroup>
           <TargetFrameworks>net7.0-windows10.0.18362;net7.0;net7.0-ios;net7.0-android</TargetFrameworks>
       </PropertyGroup>
   </Project>
   <!-- Import the TargetFramework override configuration -->
   <Import Project="../../targetframework-override.props" />
   

   Note

   If the template is created with dotnet new, the path will instead be ../targetframework-override.props

5. Create a copy of the file solution-config.props.sample next to itself, and name it solution-config.props

6. If using git, add this specific file to the .gitignore so it never gets committed. This way, each developer can keep their own version of the file without corrupting the repository.

7. Commit your changes to the repository.

At this point, your solution is ready for single-TargetFramework use.

For example, to work on net7.0-ios:

1. Before opening the solution, open the solution-config.props file and uncomment MyAppTargetFrameworkOverride to contain net7.0-ios
2. Open the MyApp-Mobile-Only.slnf solution filter in Visual Studio 2022
3. You should only see the .Mobile and Class Library projects in your solution
4. When building and debugging the app, you'll only now build for the target specified in solution-config.props.

Important

When changing the MyAppTargetFrameworkOverride value, make sure to close the solution and reload it so the build system recognizes properly the change.