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Deploying ASP.NET Applications Using Copy

Just when you though DOS was dead, the XCopy utility is back in your vocabulary. The premise of .NET applications is that files used to run an application are never locked in memory. When you start an application, be it an EXE for Windows Forms or an ASP.NET application, a shadow copy of the assemblies is loaded into memory. When methods in assemblies are executed, the shadow copy verifies that it's still the current version of the application and runs as expected.

While an application is running, you can overwrite the files that are being used; they aren't locked in memory. This was a big issue before .NET. If you needed to update a COM DLL that was being used by IIS, you had to stop the IIS server (thus ...