datagrid与DataSet结合使用中出现的索引问题

5/23/2005来源:ASP.NET技巧人气:15837

当把DataSet 绑定到Datagrid控件,

并利用DataAdapter对象修改数据库

 如:
 dim adp as new OleDbDataAdapter(stradp,conn)
 dim ocb as new OleDbCommandBuilder(adp)
 adp.DeleteCommand = ocb.GetDeleteCommand()
 adp.Update(ds,"Orders")
--------------------------------

执行删除操作时,如我们加入这样一个方法:
sub mydatagrid_delete(sender as object, e as datagridcommandeventargs)
   dim dt as new DataTable()
   dt = ds.Tables("Orders")
   dim dr as DataRow
   dr = dt.Rows(E.Item.ItemIndex)
   dr.delete
   'dr.AcceptChanges  '曾经尝试使用彻底删除,发现adp自动更新回数据库时,无法自动生成相应的sql语句

'解决删除当前页最后一项时出现的页索引异常
' *****************************************************************
   dim lastEditPage as integer = mydatagrid.currentPageIndex
   If (mydatagrid.pageCount - mydatagrid.currentPageIndex) = 1 and mydatagrid.Items.Count = 1 Then
      If mydatagrid.pageCount > 1 Then
      lastEditPage = LastEditPage - 1
   Else
      lastEditPage = 0
   End If
  
   End If
   mydatagrid.currentPageIndex = lastEditPage
' ****************************************************************


   session("orderList") = ds
   mydatagrid.edititemindex = -1
   mydatagrid.datasource = ds.tables("Orders")
   mydatagrid.databind()  
end sub

当由第一个开始逐个删除时出现了异常,发现在删除第二时,删不掉,即原来的dr(2)没有自动变为dr(1)。如果我们使用dr.delete    dr.acceptChanges则可以自动变化,但是上面说明了,则无法使用自动更新回到数据库。我们必须获得删除时的实际索引,所以就用了一个本方法,在当前的ds中另外建了一个Table,保持同步删除,但是在Table的id列中,保存实际的索引值,具体代码如下:

解决dr索引的一个办法:

       dim orderTable as new DataTable()       '建一个临时表用来保存索引,保持同步删除
       dim theNewRow as DataRow      
       dim dc as DataColumn
      
       orderTable.TableName = "orderId"
       ds.Tables.add(orderTable)
       dc = new DataColumn()
       dc.ColumnName = "id"
       orderTable.columns.add(dc)
      
       dim dcKey() as DataColumn = {orderTable.Columns("id")}
       orderTable.PRimaryKey = dcKey
      
       dim i as integer
       For i = 0 to (ds.Tables("Users").Rows.Count - 1) 
           theNewRow = orderTable.NewRow()          
           theNewRow("id") = i.toString()
           orderTable.Rows.add(theNewRow)
       Next   

上述删除功能中加的代码,替换 dr = dt.Rows(e.Item.ItemIndex):

      dim drOrder as DataRow
      drOrder = ds.Tables("orderId").Rows(E.Item.ItemIndex)
      dim currentOrder as integer = CInt(drOrder("id")) + mydatagrid.currentPageIndex * mydatagrid.PageSize
      dr = dt.Rows(currentOrder)
      drOrder.delete


如果有更新功能,则替换dr = dt.Rows(e.Item.ItemIndex):

      dim drOrder as DataRow
      drOrder = ds.Tables("orderId").Rows(E.Item.ItemIndex)
      dim currentOrder as integer = CInt(drOrder("id")) + mydatagrid.currentPageIndex * mydatagrid.PageSize
      dr = dt.Rows(currentOrder)