The type 'xxx' exists in both 'c:\WINDOWS\assembly\GAC_MSIL\xx.v7.2\xx.1063_xx\xx.dll' and 'c:\WINDOWS\assembly\GAC_MSIL\xx.v7.2\xx.61_xx\xx.dll'

I got a error message "The type 'Infragistics.WebUI.Shared.Style' exists in both 'c:\WINDOWS\assembly\GAC_MSIL\Infragistics2.WebUI.Shared.v7.2\7.2.20072.1063__7dd5c3163f2cd0cb\Infragistics2.WebUI.Shared.v7.2.dll' and 'c:\WINDOWS\assembly\GAC_MSIL\Infragistics2.WebUI.Shared.v7.2\7.2.20072.61__7dd5c3163f2cd0cb\Infragistics2.WebUI.Shared.v7.2.dll'" when try to use the bug fixed version for my project, Version 7.2.20072.1063.

To solve the problem:

First, we need to determine which version that i need to use. I need to use Version 7.2.20072.1063.
Second, we need to let out application which Version we need to use by changing web.config. Locate the <assemblies> tag (which should be under <configuration><system.web> <compilation>/<compilers>/<assemblies> ) Between the <assemblies> tag, you should enter something similar to:

<add assembly="AssemblyFileName, Version=0.0.0.0, Culture=neutral, PublicKeyToken=7DD5C3163F2CD0CB" />

<compilation debug="true">
<assemblies>
<add assembly="Infragistics2.WebUI.UltraWebTab.v7.2, Version=7.2.20072.1063, Culture=neutral, PublicKeyToken=7DD5C3163F2CD0CB"/>
<add assembly="Infragistics2.WebUI.Shared.v7.2, Version=7.2.20072.1063, Culture=neutral, PublicKeyToken=7DD5C3163F2CD0CB"/>
</assemblies>
</compilation>

Problem solved!





To know (GAC) Global Assembly Cache more:

Each computer where the common language runtime is installed has a machine-wide code cache called the global assembly cache.

Go to Start -> Settings -> Control Panel -> Administrative Tools -> Microsoft .NET Framework 2.0 Configuration

Expand the nodes and locate Assembly cache

We can add new object xxxx here.

To add manually:
Run the .NET command prompt (Start -> Programs -> Microsoft VS.NET -> VS.NET Tools -> VS.NET prompt) and start the gacutil.exe tool with -i parameter (install) and the name of the control, e.g.
gacutil.exe -i "C:\xxx\xxxx.dll"

To remove manually:
To remove xxxx from GAC
Please use the following command: gacutil.exe -u xxxx

We are able to see the different version for the object that we are trying to use. To know more about GAC, please check on MSDN.