ADO.NET 中的DATASet对象应用例子

dataset 对象的关键是理解他的无连接模式、xml格式的数据。
还有灵活运用这几个对象.
sqlconnection
sqlcommand
sqldataAdapter
DataSet
dataTable
DataRowCollection
DataCoulmnCollection
练习的代码如下:
   Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        '在此处放置初始化页的用户代码
        Dim sqlconnection As New System.Data.SqlClient.SqlConnection
        Dim sqldataset As New System.Data.DataSet         '定义DataSet对象
        sqlconnection.ConnectionString = "server=(local);uid=sa;pwd=tiantian;database=Achem56"
        sqlconnection.Open()
        Dim sqladaper As System.Data.SqlClient.SqlDataAdapter  '定义DataAdapter对象
        sqladaper = New System.Data.SqlClient.SqlDataAdapter("select  *  from user_service ", sqlconnection)
        sqlconnection.Close()
        sqladaper.Fill(sqldataset, "user_login")  '填充数据
        sqldataset.CaseSensitive = False
        Dim sqltable As System.Data.DataTable, i As Int32, j As Int32
        sqldataset.Tables("user_login").Select("id=5")  
        sqltable = sqldataset.Tables("user_login")
        '移除dataset中的数据表
        ' sqldataset.Tables.Remove("user_login")
        '判断sqltable中是否有错误
        Response.Write("sqltable中是否有错误:" & sqltable.HasErrors & "<Br>")
        '输出sqldataset中的表的个数
        'sqltable的数据筛选主要用于汇总，需要用汇总函数
        '  sqltable.Compute("count(id)", "id>30")
        'sqltable.Columns(4).Expression = "user_type *3 "
        Try
            ' Response.Write("sqldataset中的表的个数：" & sqldataset.Tables.Count & "<br>")
            '增加一个表到sqldataset
            Response.Write("<table border='0' width='100%' ><tr align='center'>")
            For i = 0 To sqltable.Columns.Count - 1                                              '循环写出数据字段的名称
                sqltable.Columns(i).Caption = i
                Response.Write("<td>" & sqltable.Columns(i).ColumnName & "</td>")     
            Next
            Response.Write("</tr>")
            '显示数据
            For i = 0 To sqltable.Rows.Count - 1                             '循环写出字段的内容
                Response.Write("<tr  align='center' >")
                For j = 0 To sqltable.Columns.Count - 1
                    Response.Write("<td>" & sqltable.Rows(i).Item(j) & "</td>")
                Next
                Response.Write("</tr>")
            Next
            Response.Write("</table>")
        Catch ex As Exception
            Response.Write(ex.Message)
        End Try
        ' Response.Write(sqltable.Columns.Count)
    End Sub