Asp.Net、Ado.net 数据库编程超级攻略_ASP.NET技巧

时间：2010-10-13 来源：蔚蓝的大海

Command对象中包含了提交给数据库系统的访问信息
OleDbCommand与SqlCommand对象，它们的基本对象与操作方法是相同的，在此仅介绍OleDbCommand的用法，SqlCommand的用法类推即可。
最常用初始化Command对象的方法是在建立Command实例中带入两个参数
OleDbCommand myComm=new OleDbCommand(strQuery,myConnection);
strQuery为SQL语句或储存过程名，myConnection是建立的Connection对象实例
Command对象主要的属性有
Connection:
CommandText:设置或获取Command对象使用的Connection对象实例
CommandType：StoredPRoceduce、TableDirect、Text（标准SQL语句）
Parameters：取得参数值集合
ExecuteReader:执行CommandText指定的SQL语句或储存过程名，返回类型为DataReader
ExecuteNonQuery:与ExecuteReader功能相同,只是返回值为执行SQL语句或储存过程受影响的记录行数
DataReader--SqlDataReader、OleDbDataReader
FieldCount:显示当前操作记录的字段总和
IsClosed：判断DataReader是否关闭
Close：关闭DataReader
GetString：以String返回指定列中的值
GetValue：以自身的类型返回指定列中的值
GetValues：返回当前记录所有字段的集合
Read：读下一条记录
例：
<% @ Page Language="C#" %>
<% @ Import Namespace="System.Data"%>
<% @ Import Namespace="System.Data.OleDb"%>
-------------------------------------------
<% @ Import Namespace="System.Data.SqlClient"%>
<Script Language="c#" Runat="Server">
OleDbDataReader dr;

String myconnstring="Provider=Microsoft.Jet.OLEDB.4.0; DataSource="+Server.MapPath(".")+"..\mdb";
string sql=".."
OleDbConnection my_conn=new OleDbConnection(myconnstring);
OleDbCommand my_comm=new OleDbCommand(sql,my_conn);
my_comm.Connection.Open();
dr=my_comm.ExecuteReader();
//DataGrid dg
dg.DataSource=dr
dg.DataBind();
</Script>
<head>
<% while(dr.Read())
...{;}
%>
</head>
DataSet DataAdapter
DataAdapter是与DataSet配套使用的
OleDbDataAdapter my_adapter=new OleDbDataAdapter();
-------------------------------------------------
SqlDataAdapter my_sqladapter=new SqlDataAdapter();
my_adapter.SelectCommand.Connection=my_conn;
或
my_adapter.UpdateCommand.Connection=my_conn;
my_adapter.DeleteCommand.Connection=my_conn;
my_adapter.InsertCommand.Connection=my_conn;
如果需要执行Sql语句，那么还必须给相应的CommandText属性赋值。http://sucai.knowsky.com/
my_adapter.SelectCommand.CommandText=strSelect;
my_adapter.UpdateCommand.CommandText=strUpdate;
my_adapter.InsertCommand.CommandText=strInsert;
my_adapter.DeleteCommand.CommandText=strDelete;
如果只是查询数据库，则可以建立DataAdapter实例时就完成上述工作
OleDbDataAdapter MyAdapter=new OleDbDataAdapter(sql,my_conn);
DataSet ds=new DataSet();
OleDbConnection my_conn=new OleDbConnection(myconnstring);
OleDbDataAdapter my_adapter=new OleDbDataAdapter(sql,my_conn);
my_adapter.fill(ds,"score");
DataGrid score;
score.DataSource=ds.Table["score"].Defaultview;
score.DataBind();
//InsertCommand
DataRow dr=ds.Table["Score"].NewRow();
dr["name"]=..

ds.Tables["Score"].Rows.Add(dr);
//update
DataAdapter.Update(ds,"Score");
//modify
DataRow dr=ds.Tables["Score"].Rows[0];
dr["name"]=;
//Delete
DataRow dr=ds.Talbes["Score"].Rows[0];
dr.Delete();
//注:
OleDbConnection my_conn=new OleDbConnection(myconnstring);
OleDbDataAdapter my_adapter=new OleDbDataAdapter(sql,my_conn);
OleDbCommandBuilder custCB=new OleDbCommandBuilder(my_adapter);//DataAdapter在数据发生改变时，并不能自动产生(Transact- SQL),所以一定要使用CommandBuilder,它能自动产生Sql语句，！就此一步
RejectChanges是DataSet,DataTable,DataRow共有的方法
使操作对象拒绝已经发生的改变，使数据复员
if(DataSet.HasErrors)
...{

DataSet.RejectChanges();
}
else...{ DataSet.AcceptChanges();}
----------------------------------------------------------------------------------------------------------------------------------
DataReader->DataTable
public static DataTable ConvertDataReaderToDataTable(SqlDataReader dataReader)
...{
   /**//**//**////定义DataTable和模式
   DataTable datatable = new DataTable();
   DataTable schemaTable = dataReader.GetSchemaTable(); //导入一个数据表的表结构

   try
   ...{ /**//**//**////动态添加表的数据列
    foreach(DataRow myRow in schemaTable.Rows)
    ...{
     DataColumn myDataColumn = new DataColumn();
     myDataColumn.DataType = myRow.GetType();
     myDataColumn.ColumnName = myRow[0].ToString();
     datatable.Columns.Add(myDataColumn);
    }

    /**//**//**////添加表的数据
    while(dataReader.Read())
    ...{
     DataRow myDataRow = datatable.NewRow();
     for(int i=0;i<schemaTable.Rows.Count;i++)
     ...{
      myDataRow[i] = dataReader[i].ToString();
     }
     datatable.Rows.Add(myDataRow);
     myDataRow = null;
    }
    schemaTable = null;

    /**//**//**////关闭数据读取器
    dataReader.Close();
    return datatable;
   }
   catch(Exception ex)
   ...{
    /**//**//**////抛出类型转换错误
    SystemError.SystemLog(ex.Message);
    throw new Exception(ex.Message,ex);
   }
}
}
}

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