TreeView 控件 无刷新填充

// MSDN
/*
下面的代码示例演示如何使用 PopulateNodesFromClient 属性启用 TreeView 控件中节点的客户端填充。请注意，启用了客户端节点填充后，会在客户端上自动填充节点，无需回发到服务器。
*/

<%@ Page Language="C#" %>
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.SqlClient" %>

<script runat="server">

  void PopulateNode(Object sender, TreeNodeEventArgs e)
  {

    // Call the appropriate method to populate a node at a particular level.
    switch(e.Node.Depth)
    {
      case 0:
        // Populate the first-level nodes.
        PopulateCategories(e.Node);
        break;
      case 1:
        // Populate the second-level nodes.
        PopulateProducts(e.Node);
        break;
      default:
        // Do nothing.
        break;
    }
   
  }

  void PopulateCategories(TreeNode node)
  {
   
    // Query for the product categories. These are the values
    // for the second-level nodes.
    DataSet ResultSet = RunQuery("Select CategoryID, CategoryName From Categories");

    // Create the second-level nodes.
    if(ResultSet.Tables.Count > 0)
    {
   
      // Iterate through and create a new node for each row in the query results.
      // Notice that the query results are stored in the table of the DataSet.
      foreach (DataRow row in ResultSet.Tables[0].Rows)
      {
       
        // Create the new node. Notice that the CategoryId is stored in the Value property
        // of the node. This will make querying for items in a specific category easier when
        // the third-level nodes are created.
        TreeNode newNode = new TreeNode();
        newNode.Text = row["CategoryName"].ToString();
        newNode.Value = row["CategoryID"].ToString();       

        // Set the PopulateOnDemand property to true so that the child nodes can be
        // dynamically populated.
        newNode.PopulateOnDemand = true;
       
        // Set additional properties for the node.
        newNode.SelectAction = TreeNodeSelectAction.Expand;
       
        // Add the new node to the ChildNodes collection of the parent node.
        node.ChildNodes.Add(newNode);
       
      }
     
    }
   
  }

  void PopulateProducts(TreeNode node)
  {

    // Query for the products of the current category. These are the values
    // for the third-level nodes.
    DataSet ResultSet = RunQuery("Select ProductName From Products Where CategoryID=" + node.Value);

    // Create the third-level nodes.
    if(ResultSet.Tables.Count > 0)
    {
   
      // Iterate through and create a new node for each row in the query results.
      // Notice that the query results are stored in the table of the DataSet.
      foreach (DataRow row in ResultSet.Tables[0].Rows)
      {
     
        // Create the new node.
        TreeNode NewNode = new TreeNode(row["ProductName"].ToString());
       
        // Set the PopulateOnDemand property to false, because these are leaf nodes and
        // do not need to be populated.
        NewNode.PopulateOnDemand = false;
       
        // Set additional properties for the node.
        NewNode.SelectAction = TreeNodeSelectAction.None;
       
        // Add the new node to the ChildNodes collection of the parent node.
        node.ChildNodes.Add(NewNode);
       
      }
     
    }

  }

  DataSet RunQuery(String QueryString)
  {

    // Declare the connection string. This example uses Microsoft SQL Server
    // and connects to the Northwind sample database.
    String ConnectionString = "server=localhost;database=NorthWind;Integrated Security=SSPI";

    SqlConnection DBConnection = new SqlConnection(ConnectionString);
    SqlDataAdapter DBAdapter;
    DataSet ResultsDataSet = new DataSet();

    try
    {

      // Run the query and create a DataSet.
      DBAdapter = new SqlDataAdapter(QueryString, DBConnection);
      DBAdapter.Fill(ResultsDataSet);

      // Close the database connection.
      DBConnection.Close();

    }
    catch(Exception ex)
    {

      // Close the database connection if it is still open.
      if(DBConnection.State == ConnectionState.Open)
      {
        DBConnection.Close();
      }
     
      Message.Text = "Unable to connect to the database.";

    }

    return ResultsDataSet;

  }

</script>

<html>
  <body>
    <form runat="server">
   
      <h3>TreeView PopulateNodesFromClient Example</h3>
   
      <asp:TreeView id="LinksTreeView"
        Font-Name= "Arial"
        ForeColor="Blue"
        EnableClientScript="true"
        PopulateNodesFromClient="true" 
        OnTreeNodePopulate="PopulateNode"
        runat="server">
        
        <Nodes>
       
          <asp:TreeNode Text="Inventory"
            SelectAction="Expand" 
            PopulateOnDemand="true"/>
       
        </Nodes>
       
      </asp:TreeView>
     
      <br><br>
     
      <asp:Label id="Message" runat="server"/>

    </form>
  </body>
</html>