方法1、
Configuration rootWebConfig =WebConfigurationManager.OpenWebConfiguration(Request.ApplicationPath);
ConnectionStringSettings connString=rootWebConfig.ConnectionStrings.ConnectionStrings["ConnectionString"];
SqlConnection myConnection = new SqlConnection(connString.ToString());
方法2、
ConnectionStringSettings connString = WebConfigurationManager.ConnectionStrings["ConnectionString"];
使用时应引用System.Web.Configuration命名空间。