风影ASP.NET基础教学 9 数据访问

在ASPNET里，我们需要和数据库进行交互。我们必须编写一个通用的类库。而且我们需要写一个和数据库无关的程序。

于是我们有了DBHelper。

   1:  using System;

   2:  using System.Collections.Generic;

   3:  using System.Linq;

   4:  using System.Web;

   5:  using System.Data.Common;

   6:  using System.Configuration;

   7:  using System.Data;

   8:  using System.Globalization;

   9:  using System.Web.UI.WebControls;

  10:   

  11:  namespace ASPNETTeach5

  12:  {

  13:      /// <summary>

  14:      /// 数据库操作命令委托

  15:      /// </summary>

  16:      /// <param name="dbCommand"></param>

  17:      /// <returns></returns>

  18:      public delegate object CommandDelegate(DbCommand dbCommand);

  19:      /// <summary>

  20:      /// DbDataReader命令委托

  21:      /// </summary>

  22:      /// <param name="dbDataReader"></param>

  23:      public delegate void DBDataReaderDelegate(DbDataReader dbDataReader);

  24:      public class DbHelper

  25:      {

  26:          private static DbHelper instance;

  27:          private ConnectionStringSettings connectionStringSettings = null;

  28:          private DbProviderFactory dbProviderFactory = null;

  29:   

  30:          public static string DataConnenctionString = "con";

  31:   

  32:          public DbHelper() {

  33:              connectionStringSettings = ConfigurationManager.ConnectionStrings[DataConnenctionString];

  34:              

  35:              if (connectionStringSettings != null) {

  36:                  if (!string.IsNullOrEmpty(connectionStringSettings.ConnectionString) && !string.IsNullOrEmpty(connectionStringSettings.ProviderName))

  37:                  {

  38:                      dbProviderFactory = DbProviderFactories.GetFactory(connectionStringSettings.ProviderName);

  39:                  }

  40:              }

  41:          }

  42:   

  43:          public DbHelper(string dbConnectionSettingName) {

  44:              if (string.IsNullOrEmpty(dbConnectionSettingName)) {

  45:                  dbConnectionSettingName = DataConnenctionString;

  46:              }

  47:              connectionStringSettings = ConfigurationManager.ConnectionStrings[DataConnenctionString];

  48:              if (connectionStringSettings != null)

  49:              {

  50:                  if (!string.IsNullOrEmpty(connectionStringSettings.ConnectionString) && !string.IsNullOrEmpty(connectionStringSettings.ProviderName))

  51:                  {

  52:                      dbProviderFactory = DbProviderFactories.GetFactory(connectionStringSettings.ProviderName);

  53:                  }

  54:              }

  55:          }

  56:   

  57:          /// <summary>

  58:          /// 获取Dbhelper对象

  59:          /// </summary>

  60:          public static DbHelper Instance {

  61:              get {

  62:                  if (instance == null)

  63:                      instance = new DbHelper();

  64:                  return instance;

  65:              }

  66:          }

  67:          /// <summary>

  68:          /// 获取链接串

  69:          /// </summary>

  70:          public string ConnectString {

  71:              get {

  72:                  return connectionStringSettings.ConnectionString;

  73:              }

  74:          } 

  75:   

  76:          /// <summary>

  77:          /// 提供者字符串

  78:          /// </summary>

  79:          public string ProviderString {

  80:              get { return connectionStringSettings.ProviderName; }

  81:          }

  82:          /// <summary>

  83:          /// 获取工厂

  84:          /// </summary>

  85:          public DbProviderFactory ProviderFactory { get { return dbProviderFactory; } }

  86:   

  87:   

  88:   

  89:          /// <summary>

  90:          /// 创建链接

  91:          /// </summary>

  92:          /// <returns></returns>

  93:          public DbConnection CreateConnection() {

  94:              if (dbProviderFactory == null)

  95:                  return null;

  96:              else

  97:              {

  98:                  DbConnection dbConnection = dbProviderFactory.CreateConnection();

  99:              

 100:                  dbConnection.ConnectionString = connectionStringSettings.ConnectionString;

 101:                  return dbConnection;

 102:              }

 103:          }

 104:   

 105:          /// <summary>

 106:          /// 执行非查询语句

 107:          /// </summary>

 108:          /// <param name="commandType"></param>

 109:          /// <param name="sql"></param>

 110:          /// <returns></returns>

 111:          public int ExecuteNonQuery(CommandType commandType,string sql) {

 112:              CommandDelegate cd = delegate(DbCommand cmd)

 113:              {

 114:                  try

 115:                  {

 116:                      return cmd.ExecuteNonQuery();

 117:                  }

 118:                  catch

 119:                  {

 120:                      return -1;

 121:                  }

 122:              };

 123:              return (int)ExecuteCmdCallback(commandType, sql, cd);

 124:          }

 125:   

 126:          /// <summary>

 127:          /// 带参数的非查询语句

 128:          /// </summary>

 129:          /// <param name="commandType"></param>

 130:          /// <param name="sql"></param>

 131:          /// <param name="pars"></param>

 132:          /// <returns></returns>

 133:          public int ExecuteNonQuery(CommandType commandType,string sql,DbParameter[] pars){

 134:              CommandDelegate cd = delegate(DbCommand cmd)

 135:              {

 136:                  return cmd.ExecuteNonQuery();

 137:              };

 138:              return (int)ExecuteCmdCallback(commandType, sql, cd, pars);

 139:          }

 140:   

 141:          /// <summary>

 142:          /// 执行带参数与委托命令的查询语句，并返回相关的委托命令

 143:          /// </summary>

 144:          /// <param name="commandType">命令类型</param>

 145:          /// <param name="sql">SQL语句</param>

 146:          /// <param name="cd">Cmd委托</param>

 147:          /// <param name="pars">参数集合</param>

 148:          /// <returns></returns>

 149:          private object ExecuteCmdCallback(CommandType commandType, string sql, CommandDelegate cd, DbParameter[] pars) {

 150:              using (DbConnection dbCnn = CreateConnection()) {

 151:                  using (DbCommand cmd = dbProviderFactory.CreateCommand()) {

 152:                      cmd.CommandType = commandType;

 153:                      cmd.CommandText = sql;

 154:                      cmd.Connection = dbCnn;

 155:                      cmd.Parameters.AddRange(pars);

 156:                      dbCnn.Open();

 157:                      return cd(cmd);

 158:   

 159:                  }

 160:              }

 161:          }

 162:          /// <summary>

 163:          /// 执行带参数与委托命令的查询语句，并返回相关的委托命令

 164:          /// </summary>

 165:          /// <param name="commandType">命令类型</param>

 166:          /// <param name="sql">SQL语句</param>

 167:          /// <param name="cd">Cmd委托</param> 

 168:          /// <returns></returns>

 169:          private object ExecuteCmdCallback(CommandType commandType, string sql, CommandDelegate commandDelegate)

 170:          {

 171:              using (DbConnection dbCon = CreateConnection())

 172:              {

 173:                  using (DbCommand cmd = dbProviderFactory.CreateCommand())

 174:                  {

 175:                      cmd.Connection = dbCon;

 176:                      cmd.CommandType = commandType;

 177:                      cmd.CommandText = sql;

 178:                      dbCon.Open();

 179:                      return commandDelegate(cmd);

 180:                  }

 181:              }

 182:          }

 183:          private object ExecuteCmdCallback(CommandType commandType,   CommandDelegate commandDelegate)

 184:          {

 185:              using (DbConnection dbCon = CreateConnection())

 186:              {

 187:                  using (DbCommand cmd = dbProviderFactory.CreateCommand())

 188:                  {

 189:                      cmd.Connection = dbCon;

 190:                      cmd.CommandType = commandType; 

 191:                      dbCon.Open();

 192:                      return commandDelegate(cmd);

 193:                  }

 194:              }

 195:          }

 196:          public bool GetReadData(string sql, DBDataReaderDelegate readdelegate)

 197:          {

 198:              bool result = false;

 199:              CommandDelegate cd = delegate(DbCommand cmd)

 200:              {

 201:                  using (DbDataReader datareader = cmd.ExecuteReader(CommandBehavior.CloseConnection))

 202:                  {

 203:                      

 204:                      readdelegate(datareader);

 205:                      return true;

 206:                  }

 207:              }; 

 208:              result = (bool)ExecuteCmdCallback(CommandType.Text, sql, cd);

 209:              return result;

 210:          }

 211:   

 212:   

 213:          public DataTable GetDataTable(CommandType commandType, string sql) {

 214:   

 215:              CommandDelegate cd = delegate(DbCommand cmd)

 216:              {

 217:                  using (DbDataReader dr = cmd.ExecuteReader())

 218:                  {

 219:                      DataTable dt = new DataTable();

 220:                      dt.Locale = CultureInfo.InvariantCulture;

 221:                      dt.Load(dr);

 222:                      return dt;

 223:                  }

 224:              };

 225:              return ExecuteCmdCallback(CommandType.Text, sql, cd) as DataTable;

 226:          }

 227:   

 228:          /// <summary>

 229:          /// 获取第一行第一列数据

 230:          /// </summary>

 231:          /// <param name="sql"></param>

 232:          /// <returns></returns>

 233:          public string GetScalar(string sql) {

 234:              CommandDelegate cd = delegate(DbCommand cmd)

 235:              {

 236:                  return cmd.ExecuteScalar();

 237:              };

 238:              object value = ExecuteCmdCallback(CommandType.Text, sql, cd);

 239:              if (value == null)

 240:                  return "";

 241:              return value.ToString();

 242:          }

 243:   

 244:   

 245:          /// <summary>

 246:          /// 获取第一行第一列数据

 247:          /// </summary>

 248:          /// <param name="sql"></param>

 249:          /// <returns></returns>

 250:          public object GetObject(string sql)

 251:          {

 252:              CommandDelegate cd = delegate(DbCommand cmd)

 253:              {

 254:                  return cmd.ExecuteScalar();

 255:              };

 256:              return ExecuteCmdCallback(CommandType.Text, sql, cd);

 257:             

 258:          }

 259:   

 260:          public DataSet GetDataSet(CommandType commandType, string sql)

 261:          {

 262:              CommandDelegate cd = delegate(DbCommand cmd)

 263:              {

 264:                  using (DbDataAdapter da = dbProviderFactory.CreateDataAdapter())

 265:                  {

 266:                      DataSet ds = new DataSet();

 267:                      ds.Locale = CultureInfo.InvariantCulture;

 268:                      da.SelectCommand = cmd;

 269:                      da.Fill(ds);

 270:                      return ds;

 271:                  }

 272:              };

 273:              return (DataSet)ExecuteCmdCallback(CommandType.Text, sql, cd);

 274:          }

 275:      }

 276:  }

 

我们如何使用呢。首先我们需要在配置文件里，配置数据库连接

   1:  <configuration>

   2:    <connectionStrings>

   3:      <add name="con" connectionString="server=.;database=BookManagement;uid=sa;pwd=sa;pooling=true" providerName="System.Data.SqlClient"/>

   4:    </connectionStrings>

   5:      <system.web>

   6:        <compilation debug="true" targetFramework="4.0" />

   7:      </system.web> 

   8:  </configuration>

 

使用方式

   1:  DbHelper.Instance.GetDataTable(System.Data.CommandType.Text, "select * from books");

我们后面的内容需要这个dbhelper来进行。