1 namespace TestDAL 2 { 3     public class DB 4     { 5         private static string[] ConnString = new[] 6         { 7             "unknown", "Data Source=163.163.1.100;Initial Catalog=xiaomi;User Id=sa;Password=1234567890;", 8             "Data Source=163.163.1.101;Initial Catalog=xiaomi;User Id=sa;Password=1234567890;" 9         };10         private static readonly ConcurrentDictionary<int, DbHelperSQLP> concurentDictionary;11         static DB()12         {13             concurentDictionary = new ConcurrentDictionary<int, DbHelperSQLP>();14         }15         private DB()16         {17         }18         public static DbHelperSQLP GetDBHelper(int id)19         {20             if (!concurentDictionary.ContainsKey(id))21                 concurentDictionary.TryAdd(id, new DbHelperSQLP(ConnString[id]));22             DbHelperSQLP db;23             bool result = concurentDictionary.TryGetValue(id, out db);24             return result ? db : null;25         }26     }27 }

 1         /// <summary> 2         /// 得到一个对象实体 3         /// </summary> 4         public xiaomi GetModel(int dbno, int id) 5         { 6             StringBuilder strSql = new StringBuilder(); 7             strSql.Append("select  top 1 id,username,password,email,ip from xiaomi "); 8             strSql.Append(" where id=@id"); 9             SqlParameter[] parameters = {10                     new SqlParameter("@id", SqlDbType.Int,4)11             };12             parameters[0].Value =http://www.mamicode.com/ id;13             DbHelperSQLP helper = DB.GetDBHelper(dbno);14             if (helper == null)15                 throw new SqlNullValueException("没有找到数据库地址");16             DataSet ds = helper.Query(strSql.ToString(), parameters);17             return ds.Tables[0].Rows.Count > 0 ? DataRowToModel(ds.Tables[0].Rows[0]) : null;18         }