class Class1
    {
        protected SqlConnection conn;
        public SqlConnection opendata()
        {
            conn = new SqlConnection(@"server=LUKE\\SQLEXPRESS;uid=sa;pwd=sa;database=luke");
            conn.Open();
            return conn;
        }

其他类可以继承Class1，然后重写opendata()方法

在button的click事件里面写就可以了