dotnet/Documentation/compatibility/ServiceBase-doesnt-propagate-OnStart-exceptions.md

## ServiceBase doesn't propagate OnStart exceptions

### Scope

Minor

### Version Introduced
4.7.1

### Source Analyzer Status

NotPlanned

### Change Description

In the .NET Framework 4.7 and earlier versions, exceptions thrown on service startup are not propagated to the caller of <xref:System.ServiceProcess.ServiceBase.Run%2A?displayProperty=nameWithType>.<br/>

Starting with applications that target the .NET Framework 4.7.1, the runtime propagates exceptions to <xref:System.ServiceProcess.ServiceBase.Run%2A?displayProperty=nameWithType> for services that fail to start.

- [x] Quirked
- [ ] Build-time break

### Recommended Action
On service start, if there is an exception, that exception will be propagated. This should help diagnose cases where services fail to start. <br/>

If this behavior is undesirable, you can opt out of it by adding the following <AppContextSwitchOverrides> element to the <runtime> section of your application configuration file:

```xml
<AppContextSwitchOverrides value="Switch.System.ServiceProcess.DontThrowExceptionsOnStart=true" />
```

If your application targets an earlier version than 4.7.1 but you want to have this behavior, add the following <AppContextSwitchOverrides> element to the <runtime> section of your application configuration file:

```xml
<AppContextSwitchOverrides value="Switch.System.ServiceProcess.DontThrowExceptionsOnStart=false" />
```

### Affected APIs
* `M:System.ServiceProcess.ServiceBase.Run(System.ServiceProcess.ServiceBase)`
* `M:System.ServiceProcess.ServiceBase.Run(System.ServiceProcess.ServiceBase[])`

### Category
Core