How to update SQL CLR to .NET 4.0 in SQL SERVER 2008 R2

Hi Techies,

I want to use .NET 4.0 class library(i.e. I'm using especially few new futures of 4.0 ) in SQL SERVER 2008 R2. But when ever i try to register assembly in SQLSERVER , getting below error

CREATE ASSEMBLY CLRSUMVarBinary FROM 'C:\CLRDefine\CLRUserDefined.dll';

CREATE ASSEMBLY for assembly 'CLRUserDefined' failed because assembly 'CLRUserDefined' failed verification. Check if the referenced assemblies are up-to-date and trusted (for external_access or unsafe) to execute in the database. CLR Verifier error messages if any will follow this message

I gone through few article, it was mentioned directly .NET 4.0 CLR can not support in SQL SERVER 2008 R2.But,

Is there any way to force SQL SERVER 2008 R2 to use CLR 4.0 ? i.e. any configuration changes ?

Regards,

Rama