# Use the .NET Framework agent with IIS Express

The .NET agent can analyze ASP.NET applications hosted on IIS Express but it takes a little bit of work to enable instrumentation on IIS Express. The Contrast tray displays a tab for IIS Express if IIS Express is installed on the server.

The Contrast tray initially displays a Set environment variables button to enable instrumentation of IIS Express-hosted applications. Selecting this button sets environment variables for the current user so that any new IIS Express process will load the .NET agent's profiler, and be instrumented and analyzed.

Once you set environment variables, the tray displays a Remove environment variables button that you can use to disable Contrast analysis of IIS Express-hosted applications.

Any instrumented applications currently running on IIS Express are displayed in the IIS Express tab along with a count of the number of URLs (without the querystring) observed.

### Note

IIS Express process instances are commonly launched by other programs such as Visual Studio or a command window. You should restart these programs after setting these user environment variables. Any programs (such as Visual Studio) that were running before you set user environment variables will consequently launch IIS Express without the environment variables, and the IIS Express-hosted application won't be instrumented and analyzed.

Setting user environment variables also causes any .NET applications launched by the user to load the Contrast Profiler. The Contrast Profiler will safely detach from any non-IIS/non-IIS Express process. Windows treats detachment of a profiler DLL as an error message in the Windows Event Log; however, you can safely ignore these errors.