namespace StringInterpolation
{
    class Program
    {
        static void Main(string[] args)
        {
            // copy Form objects to variables
            var username = Textbox1.Text;
            var password = Textbox2.Text;

            var sqlSyntaxByInterpolation = $"INSERT INTO USERS (username, password) values ('{username}', '{password}')";

            var sqlSyntaxByFormat = String.Format("INSERT INTO USERS (username, password) values '{0}','{1}'", username, password);

        }
    }
}