Partial-trust debugging requires the hosting process. If you disable the hosting process, partial-trust debugging will not work even if partial-trust security is enabled on the Security page of Project Properties. For more information, see How to: Disable the Hosting Process and How to: Debug a Partial Trust Application.

Design-time expression always uses the hosting process. Disabling the hosting process in the Project Properties disables design-time expression evaluation for Class Library projects. For other project types, design-time expression evaluation is not disabled. Instead, Visual Studio starts the actual executable and uses it for design-time evaluation without the hosting process. This difference could produce different results.

AppDomain.CurrentDomain.FriendlyName returns different results depending on whether the hosting process is enabled. If you call AppDomain.CurrentDomain.FriendlyName with the hosting process enabled, it returns app_name.vhost.exe. If you call it the hosting process disabled, it returns app_name.exe.

Assembly.GetCallingAssembly().FullName returns different results depending on whether the hosting process is enabled. If you call Assembly.GetCallingAssembly().FullName with the hosting process enabled, it returns mscorlib. If you call Assembly.GetCallingAssembly().FullName with the hosting process disabled, it returns the application name.

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