Debugging and the Hosting Process
Applies to: 
Visual Studio 
Visual Studio for Mac
Note
This article applies to Visual Studio 2017. If you're looking for the latest Visual Studio documentation, see Visual Studio documentation. We recommend upgrading to the latest version of Visual Studio. Download it here
The Visual Studio hosting process improves debugger performance and enables new debugger features, such as partial-trust debugging and design-time expression evaluation. You can disable the hosting process if you need to. The following sections describe some differences between debugging with and without the hosting process.
Note
Starting in Visual Studio 2017, the option to debug using the hosting process is no longer needed and has been removed. For more information, see Debugging: Visual Studio 2017 Aims To Speed Up Your Least Favorite Job.
Partial-Trust Debugging and Click-Once Security
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: Debug a Partial Trust Application.
Design-Time Expression Evaluation
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 Differences
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 Differences
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.