When you use the using statement the Compiler automatically throws try and finally block.inside the Finally block compiler automatically cast to IDisposable inrerface and automatically calls dispose method.
Note : using can be used only which it supports IDisposable interface.So it reduce the syntax and help to dispose method automatically.reduce the number of errors.
Using(SqlConnection con = new SqlConnection())
The compailer automatically added try - finally to ‘con’ . and do the previous operation by using IDisposable.