一、忘记sqlserver密码时，运行语句，可修改密码，记得查看账户是否被禁用

EXECUTE sp_password NULL,‘输入新密码‘,‘sa‘；

二、代码:data source一定要加上sqlexpress
            SqlConnection conn = new SqlConnection("server=localhost;Data Source=.\\SQLEXPRESS;database=doc;user=sa;password=123456");
            try
            {
                conn.Open();

            }
            catch (Exception e)
            {
                Console.WriteLine("数据库未连接成功{0}", e.Message);
            }
            finally
            {
                conn.Close();
     
            }
            Console.ReadKey();
        }

C#打开关闭数据库连接