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Posted 6 Oct 2008

Shadow Copying of Applications

, 16 Oct 2008
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Shadow copied applications aren't locked by the loader, so they can be updated/substituted at runtime.


Running an application shadow copied can be useful for purposes like auto-updating. On normal execution, the assembly gets locked by the loader and can't be substituted while it's executed. On shadow copying, all assemblies referenced are copied to a cache path, and loaded/executed from this location - so the assemblies aren't locked, and can be changed.


This technique is well known in ASP.NET, but on the application side, there's little information (even on MSDN). Therefore, I'd like to share my findings.

Using the Code

For executing an assembly from the cache path, we have to use a loader/bootstrapper. This little program creates a domain from which the application gets loaded. That means, when we want to start the application, we have to start the loader that loads the application for us.

The code for the application and all the referenced assemblies need no change.

The code for the loader is:

using System;
using System.IO;

namespace Loader
    static class Program
        static void Main()
            /* Enable shadow copying */

            // Get the startup path. Both assemblies (Loader and
            // MyApplication) reside in the same directory:
            string startupPath = Path.GetDirectoryName(

            // cache path = directory where the assemblies get
            // (shadow) copied:
            string cachePath = Path.Combine(
            string configFile = Path.Combine(
            string assembly = Path.Combine(

            // Create the setup for the new domain:
            AppDomainSetup setup = new AppDomainSetup();
            setup.ApplicationName = "MyApplication";
            setup.ShadowCopyFiles = "true"; // note: it isn't a bool
            setup.CachePath = cachePath;
            setup.ConfigurationFile = configFile;

            // Create the application domain. The evidence of this
            // running assembly is used for the new domain:
            AppDomain domain = AppDomain.CreateDomain(

            // Start MyApplication by executing the assembly:

            // After the MyApplication has finished clean up:
            Directory.Delete(cachePath, true);

Points of Interest

This simple program gives us the possibility to easily create auto updates (that replace the application's assembly).


  • 07 October 2008 - Initial release
  • 14 October 2008 - Article updated


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Günther M. FOIDL
Software Developer (Senior) Foidl Günther
Austria Austria
Engineer in combustion engine development.
Programming languages: C#, FORTRAN 95, Matlab

FIS-overall worldcup winner in Speedski (Downhill) 2008/09 and 2009/10.

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Comments and Discussions

GeneralNice Pin
Caio Kinzel Filho7-Oct-08 9:38
memberCaio Kinzel Filho7-Oct-08 9:38 
GeneralRe: Nice Pin
Günther M. FOIDL7-Oct-08 9:47
memberGünther M. FOIDL7-Oct-08 9:47 
GeneralRe: Nice Pin
Caio Kinzel Filho7-Oct-08 10:12
memberCaio Kinzel Filho7-Oct-08 10:12 

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