Shifting from Ajax 1.0.61025.0 to 3.5.0.0

If you were using the old version 1.0.61025.0, once you installed and used the new version of Ajax on your project you get the error of:

CS0433: The type 'System.Web.UI.UpdatePanel' exists in both 'c:\Windows\assembly\GAC_MSIL\System.Web.Extensions\1.0.61025.0__31bf3856ad364e35\System.Web.Extensions.dll' and 'c:\Windows\assembly\GAC_MSIL\System.Web.Extensions\3.5.0.0__31bf3856ad364e35\System.Web.Extensions.dll'

You need to add runtime tag to show which version of the Ajax you are using as;
In runtime tag;

assemblybinding xmlns="urn:schemas-microsoft-com:asm.v1"
dependentassembly
assemblyidentity name="System.Web.Extensions" publickeytoken="31bf3856ad364e35"
bindingredirect oldversion="1.0.61025.0" newversion="3.5.0.0"
/bindingredirect
dependentassembly
assemblyidentity name="System.Web.Extensions.Design" publickeytoken="31bf3856ad364e35"
bindingredirect oldversion="1.0.61025.0" newversion="3.5.0.0"
/bindingredirect
/assemblyidentity

Because both of these versions are stored in GAC with same name( and different version.

Happy coding...