Share record with User/Team in CRM 2011 using c#

Share record with User / Team

GrantAccessRequest shareToUser = new GrantAccessRequest()
 {
  Target = new EntityReference("opportunity", opportunityId), //Entity Logical name and record Id
         PrincipalAccess = new PrincipalAccess
          {
                 Principal = new EntityReference(SystemUser.EntityLogicalName, userId_or_teamId),
                 AccessMask = AccessRights.ReadAccess | AccessRights.WriteAccess | AccessRights.ShareAccess
           }

};
GrantAccessResponse grantresponse = (GrantAccessResponse)service.Execute(shareToUser);

Remove record sharing from the User / Team

ModifyAccessRequest removeSharing = new ModifyAccessRequest

 {

  Target = new EntityReference("opportunity", opportunityId), //Entity Logical name and record Id

        PrincipalAccess = new PrincipalAccess

         {

                Principal = new EntityReference(SystemUser.EntityLogicalName, userId_or_teamId),

                AccessMask = AccessRights.None

          }

   };

ModifyAccessResponse modifyresponse = (ModifyAccessResponse)service.Execute(removeSharing);