Is there a difference between sql server connection string and the express vesion?!
Yes there is a difference- the big one being you won't have AttachDbFilename in the full SQL Server.
SQL Server Express connection string:
Server=.\SQLExpress;AttachDbFilename=c:\mydbfile.mdf;Database=dbname; Trusted_Connection=Yes;
Typical normal SQL Server connection string:
Data Source=myServerAddress;Initial Catalog=myDataBase;Integrated Security=SSPI;
See connectionStrings.com for more info.