C# TreeView.BeforeExpand事件代码示例

private void showCheckedNodesButton_Click(object sender, EventArgs e)
{
    // Disable redrawing of treeView1 to prevent flickering 
    // while changes are made.
    treeView1.BeginUpdate();

    // Collapse all nodes of treeView1.
    treeView1.CollapseAll();

    // Add the checkForCheckedChildren event handler to the BeforeExpand event.
    treeView1.BeforeExpand += checkForCheckedChildren;

    // Expand all nodes of treeView1. Nodes without checked children are 
    // prevented from expanding by the checkForCheckedChildren event handler.
    treeView1.ExpandAll();

    // Remove the checkForCheckedChildren event handler from the BeforeExpand 
    // event so manual node expansion will work correctly.
    treeView1.BeforeExpand -= checkForCheckedChildren;

    // Enable redrawing of treeView1.
    treeView1.EndUpdate();
}

// Prevent expansion of a node that does not have any checked child nodes.
private void CheckForCheckedChildrenHandler(object sender, 
    TreeViewCancelEventArgs e)
{
    if (!HasCheckedChildNodes(e.Node)) e.Cancel = true;
}

// Returns a value indicating whether the specified 
// TreeNode has checked child nodes.
private bool HasCheckedChildNodes(TreeNode node)
{
    if (node.Nodes.Count == 0) return false;
    foreach (TreeNode childNode in node.Nodes)
    {
        if (childNode.Checked) return true;
        // Recursively check the children of the current child node.
        if (HasCheckedChildNodes(childNode)) return true;
    }
    return false;
}

/*
User Interfaces in C#: Windows Forms and Custom Controls
by Matthew MacDonald

Publisher: Apress
ISBN: 1590590457
*/
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;

namespace TreeViewDataBinding
{
  /// <summary>
  /// Summary description for TreeViewDataBinding.
  /// </summary>
  public class TreeViewDataBinding : System.Windows.Forms.Form
  {
    internal System.Windows.Forms.Panel Panel2;
    internal System.Windows.Forms.Panel Panel3;
    internal System.Windows.Forms.Label lblInfo;
    internal System.Windows.Forms.Label Label1;
    internal System.Windows.Forms.Splitter Splitter1;
    internal System.Windows.Forms.TreeView treeDB;
    internal System.Windows.Forms.Panel Panel1;
    internal System.Windows.Forms.Button cmdClose;
    internal System.Windows.Forms.GroupBox GroupBox1;
    /// <summary>
    /// Required designer variable.
    /// </summary>
    private System.ComponentModel.Container components = null;

    public TreeViewDataBinding()
    {
      //
      // Required for Windows Form Designer support
      //
      InitializeComponent();

      //
      // TODO: Add any constructor code after InitializeComponent call
      //
    }

    /// <summary>
    /// Clean up any resources being used.
    /// </summary>
    protected override void Dispose( bool disposing )
    {
      if( disposing )
      {
        if (components != null) 
        {
          components.Dispose();
        }
      }
      base.Dispose( disposing );
    }

    #region Windows Form Designer generated code
    /// <summary>
    /// Required method for Designer support - do not modify
    /// the contents of this method with the code editor.
    /// </summary>
    private void InitializeComponent()
    {
      this.Panel2 = new System.Windows.Forms.Panel();
      this.Panel3 = new System.Windows.Forms.Panel();
      this.lblInfo = new System.Windows.Forms.Label();
      this.Label1 = new System.Windows.Forms.Label();
      this.Splitter1 = new System.Windows.Forms.Splitter();
      this.treeDB = new System.Windows.Forms.TreeView();
      this.Panel1 = new System.Windows.Forms.Panel();
      this.cmdClose = new System.Windows.Forms.Button();
      this.GroupBox1 = new System.Windows.Forms.GroupBox();
      this.Panel2.SuspendLayout();
      this.Panel3.SuspendLayout();
      this.Panel1.SuspendLayout();
      this.SuspendLayout();
      // 
      // Panel2
      // 
      this.Panel2.Controls.AddRange(new System.Windows.Forms.Control[] {
                                         this.Panel3,
                                         this.Splitter1,
                                         this.treeDB});
      this.Panel2.Dock = System.Windows.Forms.DockStyle.Fill;
      this.Panel2.Location = new System.Drawing.Point(5, 5);
      this.Panel2.Name = "Panel2";
      this.Panel2.Size = new System.Drawing.Size(446, 264);
      this.Panel2.TabIndex = 8;
      // 
      // Panel3
      // 
      this.Panel3.Controls.AddRange(new System.Windows.Forms.Control[] {
                                         this.lblInfo,
                                         this.Label1});
      this.Panel3.Dock = System.Windows.Forms.DockStyle.Fill;
      this.Panel3.Location = new System.Drawing.Point(239, 0);
      this.Panel3.Name = "Panel3";
      this.Panel3.Size = new System.Drawing.Size(207, 264);
      this.Panel3.TabIndex = 7;
      // 
      // lblInfo
      // 
      this.lblInfo.Anchor = (((System.Windows.Forms.AnchorStyles.Top | System.Windows.Forms.AnchorStyles.Bottom) 
        | System.Windows.Forms.AnchorStyles.Left) 
        | System.Windows.Forms.AnchorStyles.Right);
      this.lblInfo.BackColor = System.Drawing.SystemColors.Window;
      this.lblInfo.Location = new System.Drawing.Point(16, 12);
      this.lblInfo.Name = "lblInfo";
      this.lblInfo.Size = new System.Drawing.Size(176, 240);
      this.lblInfo.TabIndex = 1;
      // 
      // Label1
      // 
      this.Label1.Anchor = (((System.Windows.Forms.AnchorStyles.Top | System.Windows.Forms.AnchorStyles.Bottom) 
        | System.Windows.Forms.AnchorStyles.Left) 
        | System.Windows.Forms.AnchorStyles.Right);
      this.Label1.BackColor = System.Drawing.SystemColors.Window;
      this.Label1.BorderStyle = System.Windows.Forms.BorderStyle.Fixed3D;
      this.Label1.Location = new System.Drawing.Point(4, 0);
      this.Label1.Name = "Label1";
      this.Label1.Size = new System.Drawing.Size(200, 264);
      this.Label1.TabIndex = 2;
      // 
      // Splitter1
      // 
      this.Splitter1.Location = new System.Drawing.Point(236, 0);
      this.Splitter1.Name = "Splitter1";
      this.Splitter1.Size = new System.Drawing.Size(3, 264);
      this.Splitter1.TabIndex = 6;
      this.Splitter1.TabStop = false;
      // 
      // treeDB
      // 
      this.treeDB.Dock = System.Windows.Forms.DockStyle.Left;
      this.treeDB.ImageIndex = -1;
      this.treeDB.Name = "treeDB";
      this.treeDB.SelectedImageIndex = -1;
      this.treeDB.Size = new System.Drawing.Size(236, 264);
      this.treeDB.TabIndex = 4;
      this.treeDB.AfterSelect += new System.Windows.Forms.TreeViewEventHandler(this.treeDB_AfterSelect);
      this.treeDB.BeforeExpand += new System.Windows.Forms.TreeViewCancelEventHandler(this.treeDB_BeforeExpand);
      // 
      // Panel1
      // 
      this.Panel1.Controls.AddRange(new System.Windows.Forms.Control[] {
                                         this.cmdClose,
                                         this.GroupBox1});
      this.Panel1.Dock = System.Windows.Forms.DockStyle.Bottom;
      this.Panel1.Location = new System.Drawing.Point(5, 269);
      this.Panel1.Name = "Panel1";
      this.Panel1.Size = new System.Drawing.Size(446, 36);
      this.Panel1.TabIndex = 7;
      // 
      // cmdClose
      // 
      this.cmdClose.Anchor = (System.Windows.Forms.AnchorStyles.Bottom | System.Windows.Forms.AnchorStyles.Right);
      this.cmdClose.FlatStyle = System.Windows.Forms.FlatStyle.System;
      this.cmdClose.Location = new System.Drawing.Point(372, 12);
      this.cmdClose.Name = "cmdClose";
      this.cmdClose.Size = new System.Drawing.Size(72, 24);
      this.cmdClose.TabIndex = 4;
      this.cmdClose.Text = "Close";
      this.cmdClose.Click += new System.EventHandler(this.cmdClose_Click);
      // 
      // GroupBox1
      // 
      this.GroupBox1.Anchor = ((System.Windows.Forms.AnchorStyles.Top | System.Windows.Forms.AnchorStyles.Left) 
        | System.Windows.Forms.AnchorStyles.Right);
      this.GroupBox1.Name = "GroupBox1";
      this.GroupBox1.Size = new System.Drawing.Size(444, 8);
      this.GroupBox1.TabIndex = 5;
      this.GroupBox1.TabStop = false;
      // 
      // TreeViewDataBinding
      // 
      this.AutoScaleBaseSize = new System.Drawing.Size(5, 14);
      this.ClientSize = new System.Drawing.Size(456, 310);
      this.Controls.AddRange(new System.Windows.Forms.Control[] {
                                      this.Panel2,
                                      this.Panel1});
      this.DockPadding.All = 5;
      this.Font = new System.Drawing.Font("Tahoma", 8.25F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((System.Byte)(0)));
      this.Name = "TreeViewDataBinding";
      this.Text = "TreeViewDataBinding";
      this.Load += new System.EventHandler(this.TreeViewDataBinding_Load);
      this.Panel2.ResumeLayout(false);
      this.Panel3.ResumeLayout(false);
      this.Panel1.ResumeLayout(false);
      this.ResumeLayout(false);

    }
    #endregion

    /// <summary>
    /// The main entry point for the application.
    /// </summary>
    [STAThread]
    static void Main() 
    {
      Application.Run(new TreeViewDataBinding());
    }

    private ProductDatabase DataClass = new ProductDatabase();

    private void TreeViewDataBinding_Load(object sender, System.EventArgs e)
    {
      TreeNode nodeParent;

      foreach (DataRow row in DataClass.GetCategories().Rows)
      {
        // Add the category node.
        nodeParent = treeDB.Nodes.Add(row[ProductDatabase.CategoryField.Name].ToString());
        nodeParent.ImageIndex = 0;

        // Store the disconnected category information.
        nodeParent.Tag = row;

        // Add a "dummy" node.
        nodeParent.Nodes.Add("*");
      }
    
    }

    private void treeDB_BeforeExpand(object sender, System.Windows.Forms.TreeViewCancelEventArgs e)
    {
      TreeNode nodeSelected, nodeChild;
      nodeSelected = e.Node;

      if (nodeSelected.Nodes[0].Text == "*")
      {
        // This is a dummy node.
        nodeSelected.Nodes.Clear();

        foreach (DataRow row in
          DataClass.GetProductsInCategory((DataRow)nodeSelected.Tag))
        {
          nodeChild = nodeSelected.Nodes.Add(row[ProductDatabase.ProductField.Name].ToString());

          // Store the disconnected product information.
          nodeChild.Tag = row;
          nodeChild.ImageIndex = 1;
          nodeChild.SelectedImageIndex = 1;
        }
      }

    }

    private void treeDB_AfterSelect(object sender, System.Windows.Forms.TreeViewEventArgs e)
    {
       lblInfo.Text = DataClass.GetDisplayText((DataRow)e.Node.Tag);
    }

    private void cmdClose_Click(object sender, System.EventArgs e)
    {
      this.Close();
    }
  }


  public class ProductDatabase
  {
    public class Tables
    {
      public const string Product = "Products";
      public const string Category = "Categories";
    }

    public class ProductField
    {
      public const string Name = "ModelName";
      public const string Description = "Description";
    }

    public class CategoryField
    {
      public const string Name = "CategoryName";
    }

    private DataSet dsStore;
    DataRelation relCategoryProduct;

    public ProductDatabase()
    {
      dsStore = new DataSet();

      dsStore.ReadXmlSchema(Application.StartupPath + "\\store.xsd");
      dsStore.ReadXml(Application.StartupPath + "\\store.xml");

      // Define the relation.
      relCategoryProduct = new DataRelation("Prod_Cat", 
        dsStore.Tables["Categories"].Columns["CategoryID"], 
        dsStore.Tables["Products"].Columns["CategoryID"]);
      dsStore.Relations.Add(relCategoryProduct);
    }

    public DataTable GetCategories()
    {
      return dsStore.Tables["Categories"];
    }

    public DataRow[] GetProductsInCategory(DataRow rowParent)
    {
      return rowParent.GetChildRows(relCategoryProduct);
    }

    public string GetDisplayText(DataRow row)
    {
      string text = "";

      switch (row.Table.TableName)
      {
        case Tables.Product:
          text = "ID: " + row[0] + "\n";
          text += "Name: " + row[ProductField.Name] + "\n\n";
          text += row[ProductField.Description];
          break;
      }
      return text;
    }

  }

}