.NET Runtime Bootstrapper replaces the default application host exe file, generated by MSBuild for Windows executables, with a fully featured bootstrapper that can automatically download and install .NET runtime and other missing components required by your application.
Currently, .NET offers two main ways of distributing applications: framework-dependent deployment and self-contained deployment.
Both of them come with a set of obvious and somewhat less obvious drawbacks:
Framework-dependent deployment:
Requires the user to have the correct .NET runtime installed on their machine. Not only will many users inevitably miss or ignore this requirement, the task of installing the correct .NET runtime can be very challenging for non-technical individuals. Depending on their machine and the specifics of your application, they will need to carefully examine the download page to find the installer for the right version, framework (i.e. base, desktop, or aspnet), CPU architecture, and operating system.
Comes with an application host that is not platform-agnostic. Even though the application itself (the dll file) is portable in the sense that it can run on any platform where the target runtime is supported, the application host (the exe file) is a native executable built for a specific platform (by default, the same platform as the dev machine). This means that if the application was built on Windows x64, a user running on Windows x86 will not be able to launch the application through the exe file, even if they have the correct runtime installed (dotnet myapp.dll will still work, however).
Self-contained deployment:
While eliminating the need for installing the correct runtime, this method comes at a significant file size overhead. A very basic WinForms application, for example, starts at around 100 MB in size. This can be very cumbersome when doing auto-updates, but also seems quite wasteful if you consider that the user may end up with multiple .NET applications each bringing their own runtime.
Targets a specific platform, which means that you have to provide separate binaries for each operating system and processor architecture that you intend to support. Additionally, it can also create confusion among non-technical users, who may have a hard time figuring out which of the release binaries they need to download.
Snapshots a specific version of the runtime when it's produced. This means that your application won't be able to benefit from newer releases of the runtime, potentially containing performance or security improvements, unless you deploy a new version of the application.
Is, in fact, not completely self-contained. Depending on the user's machine, they might still need to install Visual C++ runtime and required Windows updates, neither of which are packaged with the application. Although this is only required for operating systems older than Windows 10, a big portion of your users may still be using them.
.NET Runtime Bootstrapper is a project that provides an alternative third deployment option.
Combining the best of both framework-dependent and self-contained deployments, bootstrapped deployment eliminates the above-mentioned issues.
Bootstrapped deployment:
Takes care of installing the target .NET runtime automatically. All the user has to do is press "Yes" when prompted and the bootstrapper will download and install the correct version of the runtime on its own.
Can also automatically install the Visual C++ runtime and missing Windows updates, when running on older operating systems. This means that users who are still using Windows 7 will have just as seamless experience as those running on Windows 10.
Does not have any file size overhead because it doesn't package additional files. Missing prerequisites are downloaded on-demand.
Allows your application to benefit from newer releases of the runtime that the user might install in the future. When deploying your application, you are only tying it to a minimum .NET version (within the same major).
Is truly portable because the provided application host is a platform-agnostic .NET Framework 3.5 executable, which works out-of-the-box on all environments starting with Windows 7. This means that you only need to share a single distribution of your application, without worrying about different CPU architectures or operating systems.
Features
Runs the application in-process using a custom runtime host
Detects and installs missing dependencies
Required version of .NET runtime
Required Visual C++ binaries
Required Windows updates
Works out-of-the-box on Windows 7 and higher
Supports all platforms in a single executable
Integrates seamlessly within the build process
Assimilates application resources, such as version info, icons, and manifest
To add .NET Runtime Bootstrapper to your project, simply install the corresponding NuGet package.
MSBuild will automatically pick up the props and targets files provided by the package and integrate them inside the build process.
After that, no further configuration is required.
⚠ Bootstrapper only supports applications targeting .NET Core 3.0 or higher.
⚠ Bootstrapper's user experience is optimized for desktop applications.
Other application models are supported in theory but not necessarily in practice.
Publishing
In order to create a sharable distribution of your application, run dotnet publish as you normally would.
This should produce the following files in the output directory:
MyApp.exe <-- bootstrapper's application host
MyApp.exe.config <-- .NET config required by the application host
MyApp.runtimeconfig.json <-- runtime config required by the application host
MyApp.dll <-- your application
MyApp.pdb
MyApp.deps.json
[... other application dependencies ...]
Make sure to include all marked files in your application distribution.
⚠ Single-file deployment (/p:PublishSingleFile=true) is not supported by the bootstrapper.
Application host
The client-facing side of .NET Runtime Bootstrapper is implemented as a custom .NET runtime host.
Internally, it's a pre-compiled managed executable built against legacy .NET Framework v3.5, which allows it to run out-of-the-box on all operating systems starting with Windows 7.
When the user runs the application through the bootstrapper, it executes these steps:
Attempts to locate an existing .NET installation
Attempts to run the application via latest available hostfxr.dll
If that fails:
Resolves the target runtime by reading the runtimeconfig.json file
Checks if the required .NET runtime is missing
Checks if any of .NET's prerequisites are missing
Prompts the user to install the missing components
Downloads and installs the missing components
If necessary, prompts the user to reboot the system
Runs the application again
Application resources
When the bootstrapper is created, the build task injects important native resources from the target assembly into the application host:
Application manifest (resource type: 24). Can be configured by the <ApplicationManifest> project property.
Application icon (resource types: 3 and 14). Can be configured by the <ApplicationIcon> project property.
Version info (resource type: 16). Contains values configured by <FileVersion>, <InformationalVersion>, <Product>, <Copyright>, and other similar project properties.
Additionally, the version info resource is further modified to contain the following attributes:
InternalName set to the application host's file name.
OriginalName set to the application host's file name.
AppHost set to .NET Runtime Bootstrapper (vX.Y.Z) where X.Y.Z is the version of the bootstrapper.
Options
Bootstrap on build
By default, bootstrapper is only created when publishing the project (i.e. when running dotnet publish).
If you want to also have it created on every build, set the <GenerateBootstrapperOnBuild> project property to true:
<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
<OutputType>WinExe</OutputType>
<TargetFramework>net6.0-windows</TargetFramework>
<!-- ... -->
<!-- Create bootstrapper on every build, in addition to every publish -->
<GenerateBootstrapperOnBuild>true</GenerateBootstrapperOnBuild>
</PropertyGroup>
<!-- ... -->
</Project>
⚠ Bootstrapper's application host does not support debugging.
In order to retain debugging capabilities of your application during local development, keep <GenerateBootstrapperOnBuild> set to false (default).
Troubleshooting
Build task logs
If the build process does not seem to produce the bootstrapper correctly, you may be able to get more information by running the command with higher verbosity.
For example, running dotnet publish --verbosity normal on DotnetRuntimeBootstrapper.Demo project should produce output that contains the following section:
CreateBootstrapperAfterPublish:
Extracting apphost...
Extracted apphost to 'f:\Projects\Softdev\DotnetRuntimeBootstrapper\DotnetRuntimeBootstrapper.Demo\bin\Debug\net6.0-windows\DotnetRuntimeBootstrapper.Demo.exe'.
Extracted apphost config to 'f:\Projects\Softdev\DotnetRuntimeBootstrapper\DotnetRuntimeBootstrapper.Demo\bin\Debug\net6.0-windows\DotnetRuntimeBootstrapper.Demo.exe.config'.
Injecting target binding...
Injected target binding to 'DotnetRuntimeBootstrapper.Demo.exe'.
Injecting manifest...
Injected manifest to 'DotnetRuntimeBootstrapper.Demo.exe'.
Injecting icon...
Injected icon to 'DotnetRuntimeBootstrapper.Demo.exe'.
Injecting version info...
Injected version info to 'DotnetRuntimeBootstrapper.Demo.exe'.
Bootstrapper created successfully.
Application host logs
In the event of a fatal error, in addition to showing a message to the user, bootstrapper will also produce a timestamped error dump in the application's directory (for example, AppHost_Error_20211205001042.txt).
If the bootstrapper does not have sufficient permissions to create a file in that directory, it will write it to %LocalAppData%\Tyrrrz\DotnetRuntimeBootstrapper instead.
The dump has the following format:
Timestamp: 05.12.2021 0:10:42 +02:00
AppHost: .NET Runtime Bootstrapper v2.0.0 (https://github.com/Tyrrrz/DotnetRuntimeBootstrapper)
Message: System.Exception: Test failure
at DotnetRuntimeBootstrapper.AppHost.Program.Run(String[] args)
at DotnetRuntimeBootstrapper.AppHost.Program.Main(String[] args)
