[HotReloadAgent] fix possible NullReferenceException#52367
Merged
jonathanpeppers merged 4 commits intorelease/10.0.2xxfrom Jan 10, 2026
Merged
[HotReloadAgent] fix possible NullReferenceException#52367jonathanpeppers merged 4 commits intorelease/10.0.2xxfrom
NullReferenceException#52367jonathanpeppers merged 4 commits intorelease/10.0.2xxfrom
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When running on a platform like Android, startup hooks can run via
.NET's `runtimeconfig.json`, such as:
<ItemGroup>
<RuntimeHostConfigurationOption Include="STARTUP_HOOKS" Value="Microsoft.Extensions.DotNetDeltaApplier" />
</ItemGroup>
If done this way, `$DOTNET_STARTUP_HOOKS` can be `null`, leading to:
01-08 16:07:49.336 14598 14598 F mono-rt : System.NullReferenceException: Object reference not set to an instance of an object.
01-08 16:07:49.336 14598 14598 F mono-rt : at Microsoft.DotNet.HotReload.HotReloadAgent.RemoveCurrentAssembly(Type startupHookType, String environment)
01-08 16:07:49.336 14598 14598 F mono-rt : at Microsoft.DotNet.HotReload.HotReloadAgent.ClearHotReloadEnvironmentVariables(Type startupHookType)
01-08 16:07:49.336 14598 14598 F mono-rt : at StartupHook.Initialize()
01-08 16:07:49.336 14598 14598 F mono-rt : at System.Reflection.MethodBaseInvoker.InterpretedInvoke_Method(Object obj, IntPtr* args)
01-08 16:07:49.336 14598 14598 F mono-rt : at System.Reflection.MethodBaseInvoker.InvokeWithNoArgs(Object obj, BindingFlags invokeAttr)
01-08 16:07:49.336 14598 14598 F mono-rt : --- End of inner exception stack trace ---
01-08 16:07:49.336 14598 14598 F mono-rt : at System.Reflection.MethodBaseInvoker.InvokeWithNoArgs(Object obj, BindingFlags invokeAttr)
01-08 16:07:49.336 14598 14598 F mono-rt : at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
01-08 16:07:49.336 14598 14598 F mono-rt : at System.Reflection.MethodBase.Invoke(Object obj, Object[] parameters)
01-08 16:07:49.336 14598 14598 F mono-rt : at System.StartupHookProvider.CallStartupHook(StartupHookNameOrPath startupHook)
01-08 16:07:49.336 14598 14598 F mono-rt : at System.StartupHookProvider.ProcessStartupHooks(String diagnosticStartupHooks)
I think we should remove the `!` and do a better null check, to just
prevent this from happening.
I don't know yet if we'll use the env var or the `runtimeconfig.json`
by default, but this seems reasonable to fix.
With the fix, it makes it to an expected state:
01-08 16:20:20.560 17468 17468 I DOTNET : [HotReload] Environment variable DOTNET_WATCH_HOTRELOAD_NAMEDPIPE_NAME has no value
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Pull request overview
This PR fixes a NullReferenceException in the HotReloadAgent that occurs on platforms like Android where startup hooks can be configured via runtimeconfig.json instead of environment variables, resulting in a null DOTNET_STARTUP_HOOKS variable.
Key changes:
- Remove null-forgiving operator when retrieving environment variable
- Update
RemoveCurrentAssemblyto accept nullable string parameter - Use
string.IsNullOrEmpty()for more robust null/empty checking
tmat
reviewed
Jan 9, 2026
tmat
reviewed
Jan 9, 2026
tmat
approved these changes
Jan 9, 2026
This was referenced Jan 28, 2026
This was referenced Feb 12, 2026
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When running on a platform like Android, startup hooks can run via .NET's
runtimeconfig.json, such as:If done this way,
$DOTNET_STARTUP_HOOKScan benull, leading to:I think we should remove the
!and do a better null check, to just prevent this from happening.I don't know yet if we'll use the env var or the
runtimeconfig.jsonby default, but this seems reasonable to fix.With the fix, it makes it to an expected state: