Move listitems programatically to sub folder in sharepoint 2010

1. SPWeb web= properties.Web;  
2. //Folder123 is Inside root location of List  
3. string DestinationFolderName="Folder123";  
4.   
5. // Source item outside folder Folder123   
6. SPListItem listitem = properties.ListItem;  
7.   
8. SPFile listitemFile = web.GetFile(listitem.Url);  
9.   
10. //Create New Destination  URL ../Lists/Folder123/1_.000  
11. string NewDestinationUrl=listitemFile.Url.Replace(listitem.ID.ToString()+"_.000",DestinationFolderName+"/"+listitem.ID.ToString()+"_.000");   
12.   
13. //Move Item Insite Folder123  
14. listitemFile.MoveTo(NewDestinationUrl);