How to replace existing ms access database with c# code?

String baseDirectory = @"F:\Backup";

String mdbSourceFilePath = @"D:\Db\abc.mdb";

String mdbTargetFileName = "abc.mdb";

String fullDirectory = Path.Combine(baseDirectory, DateTime.Today.ToString("dddd"));

if (!Directory.Exists(baseDirectory))

Directory.CreateDirectory(baseDirectory);

if (!Directory.Exists(fullDirectory))

Directory.CreateDirectory(fullDirectory);

String mdbTargetFilePath = Path.Combine(fullDirectory, mdbTargetFileName);

File.Copy(mdbSourceFilePath, mdbTargetFilePath);

This is for backup of database. If I click on backup button this is creating backup database but if I click it again is is not overwriting existing database. I want to replace the existing database.