Create a copy of database and renaming it using mdf & ldf files

If You want to use the same directory for your mdf\ldf files You will have to (physically) rename them.
1. Detach files from local PC
2. Rename mdf and ldf files
3. Copy\Move the files to the server directory where the original Database is stored.
(In My example I used D:\Data for mdf and E:\Logs for ldf, change the path before running the script)
4. Use this code:

USE [master]
GO
CREATE DATABASE [myNewSite_db] ON 
( FILENAME = N'D:\Data\myNewSite_db.mdf' ),
( FILENAME = N'E:\Logs\myNewSite_db_log.ldf' )
FOR ATTACH
GO

Difference Between String and StringBuilder

String are Immutable (Not Modifiable). If you try to modify the string it actually creates a new string and the old string will be then ready for garbage collection.

StringBuilder when instantiated, creates a new string with predefined capacity and upto that capacity it can accodomate string without needing to create a new memory location for the string....i mean it is modifiable and can also grow as and when needed. When the string needs to be modified frequently, preferably use StringBuilder as its optimized for such situations.