问一个关于ADO连接的问题

显示全部楼层 · 2010-5-13 09:34:23

Dim myConnection As New SqlConnection()
Dim myDataAdapter As New SqlDataAdapter()
Dim myDataSet As New DataSet()
myConnection.ConnectionString = "initial catalog=pubs;integrated security=SSPI;persist security info=False;workstation id=IBM;packet size=4096"
myDataAdapter.SelectCommand = New SqlCommand()
myDataAdapter.SelectCommand.Connection = myConnection
myDataAdapter.SelectCommand.CommandText = "Select au_lname,au_fname,title,price From authors,titleauthor,titles" & _
" where authors.au_id=titleauthor.au_id and titleauthor.title_id=titles.title_id Order By au_lname,au_fname"
myDataAdapter.SelectCommand.CommandType = CommandType.Text
'myConnection.Open()
'myDataAdapter.SelectCommand.ExecuteNonQuery()
myDataAdapter.Fill(myDataSet, "aa&quot

'myConnection.Close()
grdAuthorTitles.DataSource = myDataSet
grdAuthorTitles.DataMember = "aa"
我已将打开/关闭连接注销，为何还能够得到数据填充表格？

千问 · 2010-5-13 09:34:23

Here is what I got from MSDN -- Found it after a google search on "dataadapter fill dataset connection"...
The Fill method implicitly opens the Connection that the DataAdapter is using if it finds that the connection is not already open. If Fill opened the connection, it will also close the connection when Fill is finished.

千问 · 2010-5-13 09:34:23

是不是忘记绑定了！

千问 · 2010-5-13 09:34:23

最初由 eric.li.123 发布
[B]Here is what I got from MSDN -- Found it after a google search on "dataadapter fill dataset connection"...
The Fill method implicitly opens the Connection that the DataAdapter is using if it finds that the connection is not already open. If Fill opened the connection, it will also close the connection when Fill is finished. [/B]
Bingo

千问 · 2010-5-13 09:34:23

.net的特点之一，把数据通过数据集放在内存中，不需每次连接数据源来读取数据，减少网络开销和数据库的连接负担。