在asp.net 2.0中，要动态从数据库中取出内容，动态增加结点，其实不难，比如以SQL SERVER 2000的PUBS数据库为例子，要以树型列表方式，取出作者，做为根结点，然后取出每位作者写过什么书，作为子结点，可以这样
<%@ Page Language="C#"%><%@ Import Namespace="System.Data"%><%@ Import Namespace="System.Data.SqlClient"%><%@ Import Namespace="System.Configuration"%>
<!DOCTYPE htmlPUBLIC"-//W3C//DTD XHTML 1.1//EN""http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"><head runat="server"> <title>Dynamic Population of the TreeView Control</title> <script runat=server> void Node_Populate(object sender, System.Web.UI.WebControls.TreeNodeEventArgs e) { if(e.Node.ChildNodes.Count == 0) { switch( e.Node.Depth ) { case 0: FillAuthors(e.Node); break; case 1: FillTitlesForAuthors(e.Node); break; } } }
void FillAuthors(TreeNode node) { string connString = System.Configuration.ConfigurationSettings.ConnectionStrings["NorthwindConnnection"].ConnectionString; SqlConnection connection = new SqlConnection(connString); SqlCommand command = new SqlCommand("Select * From authors",connection); SqlDataAdapter adapter = new SqlDataAdapter(command); DataSet authors = new DataSet(); adapter.Fill(authors); if (authors.Tables.Count > 0) { foreach (DataRow row in authors.Tables[0].Rows) { TreeNode newNode = new TreeNode(row["au_fname"].ToString() + " " + row["au_lname"].ToString(), row["au_id"].ToString()); newNode.PopulateOnDemand = true; newNode.SelectAction = TreeNodeSelectAction.Expand; node.ChildNodes.Add(newNode); } } }
void FillTitlesForAuthors(TreeNode node) { string authorID = node.Value; string connString = System.Configuration.ConfigurationSettings.ConnectionStrings["NorthwindConnnection"].ConnectionString; SqlConnection connection = new SqlConnection(connString); SqlCommand command = new SqlCommand("Select T.title, T.title_id From titles T" +" Inner Join titleauthor TA on T.title_id = TA.title_id " + " Where TA.au_id = '" + authorID + "'", connection); SqlDataAdapter adapter = new SqlDataAdapter(command); DataSet titlesForAuthors = new DataSet(); adapter.Fill(titlesForAuthors); if (titlesForAuthors.Tables.Count > 0) { foreach (DataRow row in titlesForAuthors.Tables[0].Rows) { TreeNode newNode = new TreeNode(row["title"].ToString(), row["title_id"].ToString()); newNode.PopulateOnDemand = false; newNode.SelectAction = TreeNodeSelectAction.None; node.ChildNodes.Add(newNode); } } }
</script></head><body> <form id="form1" runat="server"> <div> <asp:TreeViewRunat="Server" ExpandImageUrl="Images/closed.gif" CollapseImageUrl="Images/open.gif" OnTreeNodePopulate="Node_Populate" ID="tvwauthors"> <Nodes> <asp:TreeNodeText="Authors" PopulateOnDemand=trueValue="0"/> </Nodes> </asp:TreeView> </div> </form></body></html>
其中，注意ontreenodepopulate事件，是在展开树的结点时发生的，这里定义了自定义的NODE_POPULATE,在node_populate中，检查当前结点的深度，如果是0，就是根结点，于是就调用FillAuthors过程，取出所有的作者，如果深度是1，则是叶子结点，调用FillTitlesForAuthors过程。其中，要注意它们中的动态建立树结点的过程，如：
TreeNode newNode = new TreeNode(row["au_fname"].ToString() + " " + row["au_lname"].ToString(),
row["au_id"].ToString());
newNode.PopulateOnDemand = true;
newNode.SelectAction = TreeNodeSelectAction.Expand;
node.ChildNodes.Add(newNode);
其中， popluateondemand属性表明，该结点会动态扩展。
