how do you add multiple versions of the same assembly to the gac

Question

My one ASP.NET web site uses two different business object class libraries. There is a common framework DLL (CSLA.dll) between these two libraries. The problem is that one library wants to upgrade to CSLA v.4.0.1 and the other wants to remain at v.2.1.4.

How do I solve this conflict at the web site? I think I need to install both versions of the CSLA into the GAC, but I don't know how to do two things

1. Add different versions of the same DLL to the GAC (I have used gacutil -i on both CSLA.dlls. I see CSLA.dll 2.1.4 in the .NET Configuration 2.0 tool, but I see CSLA.dll 4.0.1 in C:\WINDOWS\Microsoft.NET\assembly\GAC_MSIL\Csla
2. Make the web site reference the two different versions

Thanks in advance for your help

Answer 1

In response to:

Make the web site reference the two different versions

You can force your application to use a specific version of an assembly by using Assembly Binding Redirection:

• Assembly Binding Redirection
• Configuring Assembly Binding Redirection
• The assemblyBinding config element.

In your case, the configuration should go in your web.config since the redirection is application-specific and doesn't apply to an entire version of the framework.