[mono] read $DOTNET_STARTUP_HOOKS
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Context: https://github.com/dotnet/runtime/blob/741b7157472b9a5c83a78f781ccfa8cd39707763/docs/design/features/host-startup-hook.md Context: dotnet/android#10755 Mono does not appear to read the `$DOTNET_STARTUP_HOOKS` env var when calling `System.StartupHookProvider.ProcessStartupHooks()` and only passes in `""`. So, to get the same behavior as other runtimes, you would need to workaround with something like: <RuntimeHostConfigurationOption Include="STARTUP_HOOKS" Value="MyStartupHook" Condition=" '$(UseMonoRuntime)' == 'true' " /> Let's read the env var in Mono so that it works the same way as other runtimes.
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Pull request overview
This PR adds support for reading the DOTNET_STARTUP_HOOKS environment variable in Mono runtime to match the behavior of CoreCLR and NativeAOT runtimes. Previously, Mono only passed an empty string to System.StartupHookProvider.ProcessStartupHooks(), ignoring the environment variable.
Changes:
- Mono now reads
DOTNET_STARTUP_HOOKSenvironment variable and passes its value to the startup hook processor - This aligns Mono's behavior with CoreCLR and NativeAOT implementations
- Eliminates the need for workarounds using
STARTUP_HOOKSruntime configuration option when using Mono
This was referenced Feb 4, 2026
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Context: https://github.com/dotnet/runtime/blob/741b7157472b9a5c83a78f781ccfa8cd39707763/docs/design/features/host-startup-hook.md Context: dotnet/android#10755 Mono does not appear to read the `$DOTNET_STARTUP_HOOKS` env var when calling `System.StartupHookProvider.ProcessStartupHooks()` and only passes in `""`. So, to get the same behavior as other runtimes, you would need to workaround with something like: <RuntimeHostConfigurationOption Include="STARTUP_HOOKS" Value="MyStartupHook" Condition=" '$(UseMonoRuntime)' == 'true' " /> Let's read the env var in Mono so that it works the same way as other runtimes.
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Context: https://github.com/dotnet/runtime/blob/741b7157472b9a5c83a78f781ccfa8cd39707763/docs/design/features/host-startup-hook.md
Context: dotnet/android#10755
Mono does not appear to read the
$DOTNET_STARTUP_HOOKSenv var when callingSystem.StartupHookProvider.ProcessStartupHooks()and only passes in"".So, to get the same behavior as other runtimes, you would need to workaround with something like:
Let's read the env var in Mono so that it works the same way as other runtimes.