2 ADO.NET连接类概述

2.1使用“提供者类”传输数据

2.1.1 DbConnection对象

 

代码

Imports  System.Data.Common
Imports  System.Data.SqlClient

Dim  connection  As  DbConnection  =   New  SqlConnection
connection.ConnectionString  =   " server=.;database=pubs;trusted_connection=true "
connection.Open()
' 做许多很酷的工作
connection.Close()

 

 

2.1.1.1 配置ODBC连接字符串

2.1.1.2 配置OLEDB连接字符串

2.1.1.3 配置SQLSERVER连接字符串

persist security info=false;

integrated security=sspi;

database=northwind;

server=localhost;

 

network library=dbmssocn;

data source=10.1.2.3,1433;

initial catalog=MydbName;

user id=myusername;

password=xlddd;

 

data source=.\sqlexpress;

attachdbfilename=c:\pubs.mdf;

user instance=true;

 

data source=.\sqlexpress;

attachdbfilename=|dataDirectory|\pubs.mdf;

integrated security=true;

user instance=true;

 

Dim  path  As   String   =  AppDomain.CurrentDomain.GetData( " DataDirectory " )
If  path  =   String .Empty  Then
    path  =  AppDomain.CurrentDomain.BaseDirectory
End   If
return  path

 

 

2.1.1.4 将连接字符串保存到应用程序配置文件中

 

代码

Imports  System.Configuration

Dim  pubs  As  ConnectionStringSettings
pubs  =  ConfigurationManager.ConnectionStrings( " PubsData " )

Dim  name  As   String   =  pubs.Name
Dim  provider  As   String   =  pubs.ProviderName
Dim  cnString  As   String   =  pubs.ConnectionString

 

 

2.1.1.5 GetSchema方法

 

代码

Imports  System.Configuration
Imports  System.Data.Common
Imports  System.Data.SqlClient

Dim  pubs  As  ConnectionStringSettings
pubs  =  ConfigurationManager.ConnectionStrings( " PubsData " )

Dim  connection  As  DbConnection  =   New  SqlConnection
connection.ConnectionString  =  pubs.ConnectionString
connection.Open()
Dim  schema  As  DataTable  =  connection.GetSchema
connection.Close()

DataGridView1.DataSource  =  schema

 

 

在选中不同行时，用数据填充第二个DataGridView

 

代码

     Private   Sub  DataGridView1_SelectionChanged( ByVal  sender  As   Object ,  ByVal  e  As  EventArgs)  Handles  DataGridView1.SelectionChanged
         Dim  schema  As  DataTable  =  DataGridView1.DataSource
         Dim  currentRow  As  DataRow  =  schema.Rows(DataGridView1.CurrentCell.RowIndex)

         Dim  collectionName  As   String   =  currentRow( " CollectionName " )

         Dim  pubs  As  ConnectionStringSettings
        pubs  =  ConfigurationManager.ConnectionStrings( " PubsData " )
         Dim  connection  As  DbConnection  =   New  SqlConnection
        connection.ConnectionString  =  pubs.ConnectionString
        connection.Open()

         Dim  schema2  As  DataTable  =  connection.GetSchema(collectionName)

        connection.Close()
        DataGridView2.DataSource  =  schema
     End Sub

 2.1.2 DbCommand对象

 

代码

Imports  System.Configuration
Imports  System.Data.Common
Imports  System.Data.SqlClient

Dim  pubs  As  ConnectionStringSettings
pubs  =  ConfigurationManager.ConnectionStrings( " PubsData " )
Dim  connection  As  DbConnection  =   New  SqlConnection
connection.ConnectionString  =  pubs.ConnectionString

Dim  cmd  As  DbCommand  =  connection.CreateCommand
cmd.CommandType  =  CommandType.StoredProcedure
cmd.CommandText  =   " uspGetCustomerById "

  

2.1.2.1 DbParameter对象

 

代码

Imports  System.Configuration
Imports  System.Data.Common
Imports  System.Data.SqlClient

Dim  pubs  As  ConnectionStringSettings
pubs  =  ConfigurationManager.ConnectionStrings( " PubsData " )
Dim  connection  As  DbConnection  =   New  SqlConnection
connection.ConnectionString  =  pubs.ConnectionString

Dim  cmd  As  DbCommand  =  connection.CreateCommand
cmd.CommandType  =  CommandType.StoredProcedure
cmd.CommandText  =   " uspGetCustomerById "

Dim  parm  As  DbParameter  =  cmd.CreateParameter
parm.ParameterName  =   " @Id "
parm.Value  =   " AROUT "
cmd.Parameters.Add(parm)

  

2.1.2.2 ExecuteNonQuery方法

 

代码

Dim  pubs  As  ConnectionStringSettings
pubs  =  ConfigurationManager.ConnectionStrings( " PubsData " )
Dim  connection  As  DbConnection  =   New  SqlConnection
connection.ConnectionString  =  pubs.ConnectionString

Dim  cmd  As  DbCommand  =  connection.CreateCommand
cmd.CommandType  =  CommandType.Text
cmd.CommandText  =   " UPDATE sales SET qty = qty + 1 WHERE qty > 50 "
connection.Open()
Dim  count  As   Integer   =  cmd.ExecuteNonQuery
connection.Close()

  

2.1.2.3 ExecuteScalar方法

 

代码

Dim  pubs  As  ConnectionStringSettings
pubs  =  ConfigurationManager.ConnectionStrings( " PubsData " )
Dim  connection  As  DbConnection  =   New  SqlConnection
connection.ConnectionString  =  pubs.ConnectionString

Dim  cmd  As  DbCommand  =  connection.CreateCommand
cmd.CommandType  =  CommandType.Text

cmd.CommandText  =   " SELECT COUNT(*) FROM Sales "
connection.Open()
Dim  count  As   Integer   =  cmd.ExecuteScalar
connection.Close()
MessageBox.Show(count.ToString)

 

2.1.2.4 ExecuteReader方法

 

代码

Dim  pubs  As  ConnectionStringSettings
pubs  =  ConfigurationManager.ConnectionStrings( " PubsData " )
Dim  connection  As  DbConnection  =   New  SqlConnection
connection.ConnectionString  =  pubs.ConnectionString

Dim  cmd  As  DbCommand  =  connection.CreateCommand
cmd.CommandType  =  CommandType.Text

cmd.CommandText  =   " SELECT stor_id, ord_num FROM Sales "
connection.Open()
Dim  rdr  As  DbDataReader  =  cmd.ExecuteReader
While  rdr.Read
    MessageBox.Show(rdr( " stor_id " )  &   " :  "   &  rdr( " ord_num " ))
End   While
connection.Close()

 

2.1.3 DbDataReader 对象

 

代码

Dim  pubs  As  ConnectionStringSettings
pubs  =  ConfigurationManager.ConnectionStrings( " PubsData " )
Dim  connection  As  DbConnection  =   New  SqlConnection
connection.ConnectionString  =  pubs.ConnectionString

Dim  cmd  As  DbCommand  =  connection.CreateCommand
cmd.CommandType  =  CommandType.Text

cmd.CommandText  =   " SELECT pub_id, pub_name FROM publishers "
connection.Open()
Dim  rdr  As  DbDataReader  =  cmd.ExecuteReader
Dim  publishers  As   New  DataTable
publishers.Load(rdr, LoadOption.Upsert)
connection.Close()

 

 2.1.4 使用多个活动结果集对单个连接执行多条命令

 

代码

         Dim  pubs  As  ConnectionStringSettings
        pubs  =  ConfigurationManager.ConnectionStrings( " PubsDataMars " )
         Dim  connection  As  DbConnection  =   New  SqlConnection
        connection.ConnectionString  =  pubs.ConnectionString

         Dim  cmd  As  DbCommand  =  connection.CreateCommand
        cmd.CommandType  =  CommandType.Text

        cmd.CommandText  =   " SELECT stor_id, stor_name FROM stores "
        connection.Open()
         Dim  rdr  As  DbDataReader  =  cmd.ExecuteReader
         While  rdr.Read
             Dim  salesCmd  As  DbCommand  =  connection.CreateCommand
            salesCmd.CommandType  =  CommandType.Text
            salesCmd.CommandText  =   " SELECT SUM(qty) FROM sales where (stor_id = @storeId) "

             Dim  parm  As  DbParameter  =  cmd.CreateParameter
            parm.ParameterName  =   " @storeId "
            parm.Value  =  rdr( " stor_id " )
            salesCmd.Parameters.Add(parm)

             Dim  qtySales  As   Object   =  salesCmd.ExecuteScalar

            MessageBox.Show(rdr( " stor_name " ).ToString()  &   " :  "   &  qtySales.ToString())
         End   While
        connection.Close()

 

 2.1.5 使用SqlBulkCopy对象执行批量复制操作

 

代码

     Private   Sub  btnBulkCopy_Click( ByVal  sender  As  System.Object,  ByVal  e  As  System.EventArgs)  Handles  btnBulkCopy.Click
         Dim  pubs  As  ConnectionStringSettings
        pubs  =  ConfigurationManager.ConnectionStrings( " PubsData " )
         Dim  connection  As  DbConnection  =   New  SqlConnection
        connection.ConnectionString  =  pubs.ConnectionString

         Dim  bulkCopy  As  ConnectionStringSettings
        bulkCopy  =  ConfigurationManager.ConnectionStrings( " BulkCopy " )
         Dim  bulkCopyConnection  As  DbConnection  =   New  SqlConnection
        bulkCopyConnection.ConnectionString  =  bulkCopy.ConnectionString

         Dim  cmd  As  DbCommand  =  connection.CreateCommand
        cmd.CommandType  =  CommandType.Text
        cmd.CommandText  =   " SELECT stor_name FROM stores "

        connection.Open()
        bulkCopyConnection.Open()

         Dim  rdr  As  DbDataReader  =  cmd.ExecuteReader
         Dim  bc  As   New  SqlBulkCopy(bulkCopyConnection)
        bc.DestinationTableName  =   " StoreList "
        bc.WriteToServer(rdr)

        connection.Close()
        bulkCopyConnection.Close()

        MessageBox.Show( " Done with bulk copy " )
     End Sub

 

 

 2.1.6 DbDataAdapter对象

2.1.6.1 使用Fill方法

 

代码

Dim  pubs  As  ConnectionStringSettings
pubs  =  ConfigurationManager.ConnectionStrings( " PubsData " )
Dim  connection  As  DbConnection  =   New  SqlConnection
connection.ConnectionString  =  pubs.ConnectionString
Dim  cmd  As  SqlCommand  =  connection.CreateCommand
cmd.CommandType  =  CommandType.Text
cmd.CommandText  =   " SELECT pub_id,pub_name FROM publishers "

Dim  pubsDataSet  As   New  DataSet( " Pubs " )
Dim  da  As   New  SqlDataAdapter(cmd)
da.Fill(pubsDataSet,  " publishers " )

  

2.1.6.2 使用Update方法将修改结果保存到数据库中

  

代码

     Dim  pubs  As  ConnectionStringSettings
    pubs  =  ConfigurationManager.ConnectionStrings( " PubsData " )
     Dim  connection  As  DbConnection  =   New  SqlConnection
    connection.ConnectionString  =  pubs.ConnectionString

     Dim  cmd  As  SqlCommand  =  connection.CreateCommand
    cmd.CommandType  =  CommandType.Text
    cmd.CommandText  =   " SELECT * FROM publishers "

     Dim  pubsDataSet  As   New  DataSet( " Pubs " )
     Dim  da  As   New  SqlDataAdapter(cmd)
     Dim  bldr  As   New  SqlCommandBuilder(da)
    da.Fill(pubsDataSet,  " publishers " )
     ' modify data here
    pubsDataSet.Tables( " publishers " ).Rows( 0 )( " pub_name " )  =   " Hello "
    pubsDataSet.Tables( " publishers " ).Rows.Add( " 9911 " ,  " tailspin Toys " ,  " Paris " ,  Nothing ,  " France " )
    da.Update(pubsDataSet,  " publishers " )

    MessageBox.Show( " Update Complete " )

 

 

2.1.6.3 将修改结果批量保存到数据库中

 

代码

Public   Class  Form1
     Public   WithEvents  da  As   New  SqlDataAdapter
     Public  sb  As   New  StringBuilder

     Private   Sub  da_RowUpdated( ByVal  sender  As   Object ,  ByVal  e  As  System.Data.SqlClient.SqlRowUpdatedEventArgs)  Handles  da.RowUpdated
        sb.Append( " Rows:  "   &  e.RecordsAffected.ToString  &  vbCrLf)
     End Sub

     Private   Sub  btnUpdateBatch_Click( ByVal  sender  As  System.Object,  ByVal  e  As  System.EventArgs)  Handles  btnUpdateBatch.Click
         Dim  pubs  As  ConnectionStringSettings
        pubs  =  ConfigurationManager.ConnectionStrings( " PubsData " )
         Dim  connection  As  DbConnection  =   New  SqlConnection
        connection.ConnectionString  =  pubs.ConnectionString

         Dim  cmd  As  SqlCommand  =  connection.CreateCommand
        cmd.CommandType  =  CommandType.Text
        cmd.CommandText  =   " SELECT * FROM publishers "

         Dim  pubsDataSet  As   New  DataSet( " Pubs " )
        da.SelectCommand  =  cmd
         Dim  bldr  As   New  SqlCommandBuilder(da)
        da.Fill(pubsDataSet,  " publishers " )

         ' modify data here
         For   Each  dr  As  DataRow  In  pubsDataSet.Tables( " publishers " ).Rows
            dr( " pub_name " )  =   " Updated Toys "
         Next

        da.UpdateBatchSize  =   3
        da.Update(pubsDataSet,  " publishers " )

        MessageBox.Show(sb.ToString)
     End Sub

End Class

  

2.1.7 DbProviderFactory类

 

代码

Imports  System.Configuration
Imports  System.Data.Common
Imports  System.Data.SqlClient

Public   Class  DbProviderFactoryExample
     Public   Enum  DbProvider
        SqlClient
        OleDb
        Odbc
        Oracle
     End Enum

     Public   Function  GetConnection()  As  IDbConnection
         ' Get the provider from the config file
         Dim  provider  As  DbProvider  =  System.Enum.Parse( GetType (DbProvider), ConfigurationManager.AppSettings( " provider " ).ToString)
         Dim  connection  As  IDbConnection  =   Nothing
         Select   Case  (provider)
             Case  DbProvider.SqlClient
                connection  =   New  System.Data.SqlClient.SqlConnection
             Case  DbProvider.OleDb
                connection  =   New  System.Data.OleDb.OleDbConnection
             Case  DbProvider.Odbc
                connection  =   New  System.Data.Odbc.OdbcConnection
             Case  DbProvider.Oracle
                connection  =   New  System.Data.OracleClient.OracleConnection
         End   Select
         Return  connection
     End Function

     ' Get the singleton instance
     Dim  factory  As  DbProviderFactory  =  SqlClientFactory.Instance
     Function  GetProviderConnection()  As  DbConnection
         Dim  connection  As  DbConnection  =  factory.CreateConnection
        connection.ConnectionString  =   " Data Source=.\ sqlexpress; "  _
             &   " AttachDbFilename=|DataDirectory|\pubs.mdf; "  _
             &   " Integrated Security=true;user instance=true "
         Return  connection
     End Function

     Function  GetData( ByVal  commandText  As   String ,  ByVal  commandType  As  CommandType)  As  DataTable
         ' Get SqlDbCommand
         Dim  cmd  As  DbCommand  =  factory.CreateCommand
        cmd.Connection  =  GetProviderConnection()
         If  (cmd.Connection  Is   Nothing )  Then
             Return   Nothing
         End   If
        cmd.CommandText  =  commandText
        cmd.CommandType  =  commandType
        cmd.Connection.Open()
         Dim  dt  As   New  DataTable
         ' Get SqlDataReader and populate data table
        dt.Load(cmd.ExecuteReader)
        cmd.Connection.Close()
         Return  dt
     End Function
End Class

2.1.8 DbProviderFactories类

2.1.9 枚举数据源

 

代码

Imports  System.Data.Common

Public   Class  frmProviderFactories
     Dim  providersList  As  DataTable  =   Nothing

     Private   Sub  Button1_Click( ByVal  sender  As  System.Object,  ByVal  e  As  System.EventArgs)  Handles  Button1.Click
        providersList  =  DbProviderFactories.GetFactoryClasses
        DataGridView1.DataSource  =  providersList
     End Sub

     Sub  DataGridView1_RowHeaderMouseDoubleClick( ByVal  sender  As   Object ,  ByVal  e  As  System.Windows.Forms.DataGridViewCellMouseEventArgs) _

　　Handles  DataGridView1.RowHeaderMouseDoubleClick
         Dim  providerRow  As  DataRow  =  providersList.DefaultView(e.RowIndex).Row
         Dim  factory  As  DbProviderFactory  =  DbProviderFactories.GetFactory(providerRow)

         Dim  sources  As  DataTable  =  factory.CreateDataSourceEnumerator.GetDataSources
         Dim  f  As  frmSources  =   New  frmsources
        f.DataSources  =  sources
         If  f.ShowDialog  <>  Windows.Forms.DialogResult.OK  Then
             Return
         End   If

         Dim  selectedSource  As  DataRow  =  f.SelectedSource
     End Sub
End Class

 

 

数据源列表对话框

 

代码

Public   Class  frmSources
     Dim  _DataSources  As  DataTable
     Public   Property  DataSources()  As  DataTable
         Get
             Return  _DataSources
         End   Get
         Set ( ByVal  value  As  DataTable)
            _DataSources  =  value
         End   Set
     End Property

     Dim  _SelectedSource  As  DataRow
     Public   Property  SelectedSource()  As  DataRow
         Get
             Return  _SelectedSource
         End   Get
         Set ( ByVal  value  As  DataRow)
            _SelectedSource  =  value
         End   Set
     End Property

     Sub  DataGridView1_MouseDoubleClick( ByVal  sender  As   Object ,  ByVal  e  As  System.Windows.Forms.MouseEventArgs) _
     Handles  DataGridView1.MouseDoubleClick
        SelectedSource  =   DirectCast (DataGridView1.DataSource, DataTable).DefaultView(DataGridView1.CurrentCell.RowIndex).Row
        DialogResult  =  Windows.Forms.DialogResult.OK
     End Sub
End Class