Problem About Pass A Big String (over 8000 Characters) To A Variable Nvarchar(max) In Stored Procedure In SQL 2005!

Problem about pass a big string (over 8000 characters) to a variable nvarchar(max) in stored procedure in SQL 2005!

I know that SQL 2005 define a new field nvarchar(max) which can stored 2G size string.

I have made a stored procedure Hellocw_ImportBookmark, but when I pass a big string  to  @Insertcontent , the stored procedure can't be launch! why?

 

 

 

 

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create procedure Hellocw_ImportBookmark
  @userId         varchar(80),
  @FolderId       varchar(80),
  @Insertcontent  nvarchar(max)

as
  declare @contentsql nvarchar(max);
  set @contentsql=N'update cw_bookmark set Bookmark.modify(''declare namespace x="http://www.hellocw.com/onlinebookmark"; insert '+
                    @Insertcontent+' as last into (//x:Folder[@Id="'+@FolderId+'"])[1]'')  where userId='''+@userID+'''';
  exec sp_executesql @contentsql;