Add new MddBootstrapInitialize2(...options)
If Bootstrap Initialize fails...

...Write to the eventlog

...Optionally

• DebugBreak
• DebugBreak if a debugger is attached to the process
• FailFast
• MessageBox (modeled after .NET's) asking if you'd like to install the WindowsAppRuntime and if so, ShellExecute(url) to the download page

The optional behavior is triggered by the new MddBootstrapInitialize(...options) parameter or by environment variables

SET MICROSOFT_WINDOWSAPPRUNTIME_BOOTSTRAP_INITIALIZE_DEBUGBREAK=1
SET MICROSOFT_WINDOWSAPPRUNTIME_BOOTSTRAP_INITIALIZE_SHOWUI=1
SET MICROSOFT_WINDOWSAPPRUNTIME_BOOTSTRAP_INITIALIZE_FAILFAST=1

Tested via manual testing (HelloWorldAdvancedCPP.exe) under debugger with memory fiddling and running after setting environment variables.

*.targets updated to provide build-time control (instead of AutoInitialize always unconditionally enabled like in 1.0).

• To disable the auto-initializer the auto-initialize set the property WindowsAppSDKBootstrapAutoInitialize=false
• If the auto-initalizer is enabled you can define properties to control the options passed to MddBootstrapInitialize2()
  • WindowsAppSDKBootstrapAutoInitializeOptions_Default=true -- use the default options (OnNoMatch_ShowUI)
  • WindowsAppSDKBootstrapAutoInitializeOptions_None=true -- use no options (None)
  • WindowsAppSDKBootstrapAutoInitializeOptions_*=true -- enable the option where * is one or more of the following
    • OnError_DebugBreak
    • OnError_DebugBreak_IfDebuggerAttached
    • OnError_FailFast
    • OnNoMatch_ShowUI
    • OnPackageIdentity_NoOp

For example, to disable the auto-initializer add to your *proj file:

<PropertyGroup>
    <WindowsAppSDKBootstrapAutoInitialize>false</WindowsAppSDKBootstrapAutoInitialize>
</PropertyGroup>

or to enable the auto-initializer (default) but use the DebugBreak+FailFast options (instead of the default)

<PropertyGroup>
    <WindowsAppSDKBootstrapAutoInitializeOptions_OnError_DebugBreak>true</WindowsAppSDKBootstrapAutoInitializeOptions_OnError_DebugBreak>
    <WindowsAppSDKBootstrapAutoInitializeOptions_OnNoMatch_ShowUI>true</WindowsAppSDKBootstrapAutoInitializeOptions_OnNoMatch_ShowUI>
</PropertyGroup>

https://task.ms/38570577 Improve Bootstrap error discoverability+diagnostics
https://task.ms/38497503 Improve Bootstrap AutoInitialize discoverability+diagnostics
https://task.ms/38570355 MddBootstrapInitializeOptions_OnPackageIdentity_NOOP