数据库调用，常用类，喜欢用的一种形式，可以根据自己的情况修改使用。

namespace DAL
{
    public class db
    {
        public static string connstr()
        {
            return ConfigurationManager.ConnectionStrings["dbcon"].ToString();
        }
        public static string connstrAll()
        {
            return ConfigurationManager.ConnectionStrings["dbconall"].ToString();
        }

        public static string connstr_xls(string path2)
        {
            string strConn = "Provider=Microsoft.Jet.Oledb.4.0;Data Source=" + HttpContext.Current.Server.MapPath(path2) + ";Extended Properties='Excel 8.0;HDR=Yes;IMEX=1;'";
            return strConn;
        }

        public static string connstr_xlsx(string path2)
        {
            string strConn = "Provider=Microsoft.ACE.Oledb.12.0;Data Source=" + HttpContext.Current.Server.MapPath(path2) + ";Extended Properties='Excel 12.0;HDR=Yes;IMEX=1;'";
            return strConn;
        }

        public static string connstr_xls_HDRNo(string path2)
        {
            string strConn = "Provider=Microsoft.Jet.Oledb.4.0;Data Source=" + HttpContext.Current.Server.MapPath(path2) + ";Extended Properties='Excel 8.0;HDR=No;IMEX=1;'";
            return strConn;
        }

        public static string connstr_xlsx_HDRNo(string path2)
        {
            string strConn = "Provider=Microsoft.ACE.Oledb.12.0;Data Source=" + HttpContext.Current.Server.MapPath(path2) + ";Extended Properties='Excel 12.0;HDR=No;IMEX=1;'";
            return strConn;
        }

        public static void ConnOpen(SqlConnection conn)
        {
            //try
            //{
                if (conn.State == ConnectionState.Closed)
                {
                    //conn.ConnectionString = connstr();
                    conn.Open();
                }
                else
                {
                    conn.Close();
                    conn.Open();
                }

        }
        public static SqlConnection Conn()
        {
            SqlConnection conn = new SqlConnection(connstr());
            return conn;
        }
        public static void ConnClose(SqlConnection conn)
        {
            conn.Close();
        }
    }
}