How to use impersonateuser in case of claim based authenticated site.

Only app pool acc is having impersonation permission.

In case of  claim based authenticated site with SPSecurity.RunWithElevatedPrivileges, while opening the K2 connection, K2 connection is running with logged in user acount instead of app pool account. Since logged in user is not having impersonation permission so throwing error saying "user does not have permission to impersonate user". 

In case of windows authenticate site with SPSecurity.RunWithElevatedPrivileges, while opening K2 connection, K2 connection is running with app pool account. so I am able to use impersoateuser. it is working fine.

Regards,

Nanda