程序代码：

public static class DBHelper
    {
        private static SqlConnection connection;
        public static SqlConnection Connection
        {
            get
            {
                //从配置文件中获取连接数据库的连接字符串
                string connectionString=ConfigurationManager .ConnectionStrings ["HRConStr"].ConnectionString;
                if(connection==null )
                {
                    connection =new SqlConnection (connectionString );
                    connection.Open ();
                }
                else if(connection.State==System.Data .ConnectionState .Closed )
                {
                    connection .Open ();
                }
                else if(connection .State==System .Data.ConnectionState .Broken )
                {
                    connection.Close ();
                    connection.Open ();
                }
                return connection ;
            }
         }
        //不带参数的执行命令
      
        public static int ExecuteCommand(string safeSql)
        {
            SqlCommand cmd=new SqlCommand (safeSql,Connection );
            int result=cmd.ExecuteNonQuery ();
            return result ;
            connection.Close();//提示connection不能访问，改成Connection也是那个提示，请问是怎么回事呢？
        }
}