Question

我在网上找到了这个代码。它可以工作，但由于某种原因，它会加载文件目录两次。

namespace DockSample.Controls
{
    using System;
    using System.Collections.Generic;
    using System.Text;
    using System.Windows.Forms;
    using System.IO;
    using System.Drawing;
    using Microsoft.VisualBasic.FileIO;
    using DockSample;



    //TODO: Add options for filtering by robot
       public class SolutionExplorer : TreeView
        {

            public SolutionExplorer()
            {
                this.BeforeExpand += customBeforeExpand;
                this.Nodes.Clear();
                CreateTree(this);
            }

            private bool CreateTree(TreeView treeView)
            {

                bool returnValue = false;

                try
                {
                    // Create Desktop
                    TreeNode desktop = new TreeNode();
                  //  desktop.Text = "Desktop";
                  //  desktop.Tag = "Desktop";
                  //  desktop.Nodes.Add("");
                  //  treeView.Nodes.Add(desktop);
                    // Get driveInfo
                    foreach (DriveInfo drv in DriveInfo.GetDrives())
                    {

                        TreeNode fChild = new TreeNode();
                        if (drv.DriveType == DriveType.CDRom)
                        {
                            fChild.ImageIndex = 1;
                            fChild.SelectedImageIndex = 1;
                        }
                        else if (drv.DriveType == DriveType.Fixed)
                        {
                            fChild.ImageIndex = 0;
                            fChild.SelectedImageIndex = 0;
                        }
                        fChild.Text = drv.Name;
                        fChild.Nodes.Add("");
                        treeView.Nodes.Add(fChild);
                        returnValue = true;
                    }

                }
                catch 
                {
                    returnValue = false;
                }
                return returnValue;

            }

            /* Method :EnumerateDirectory
            * Author : Chandana Subasinghe
            * Date : 10/03/2006
            * Discription : This is use to Enumerate directories and files
            * 
            */
            public TreeNode EnumerateDirectory(TreeNode parentNode, List<string> thisFilter)
            {

                try
                {
                    DirectoryInfo rootDir;

                    // To fill Desktop
                    Char[] arr = { '\\' };
                    string[] nameList = parentNode.FullPath.Split(arr);
                    string path = "";

                    if (nameList.GetValue(0).ToString() == "Desktop")
                    {
                        path = SpecialDirectories.Desktop + "\\";

                        for (int i = 1; i < nameList.Length; i++)
                        {
                            path = path + nameList[i] + "\\";
                        }

                        rootDir = new DirectoryInfo(path);
                    }
                    // for other Directories
                    else
                    {

                        rootDir = new DirectoryInfo(parentNode.FullPath + "\\");
                    }

                    parentNode.Nodes[0].Remove();
                    foreach (DirectoryInfo dir in rootDir.GetDirectories())
                    {

                        TreeNode node = new TreeNode();
                        node.Text = dir.Name;
                        node.Nodes.Add("");
                        parentNode.Nodes.Add(node);
                    }
                    //Fill files
                    foreach (FileInfo file in rootDir.GetFiles())
                    {
                        if (isValidFilter(getExtention(file.Name)))
                        {
                            TreeNode node = new TreeNode();
                            node.Text = file.Name;
                            node.ImageIndex = 2;
                            node.SelectedImageIndex = 2;
                            parentNode.Nodes.Add(node);
                        }
                    }



                }

                catch 
                {
                }

                return parentNode;
            }
            private bool isValidFilter(string ext)
            {
                bool result = false;
                foreach(string s in filter)
                {
                    if (ext == s)
                        result =  true;

                }

                return result;
            }
            private string getExtention(string filename)
            {
                return filename.Substring(filename.IndexOf("."));
            }
            private void customBeforeExpand(object sender, TreeViewCancelEventArgs e)
            {
                if (e.Node.Nodes[0].Text == "")
                {
                    TreeNode node = this.EnumerateDirectory(e.Node,filter);
                }
            }
            private List<string> filter = new List<string>();
            public List<string> Filter
            {
                get { return filter; }
                set { filter = value; }
            }
            private void InitializeComponent()
            {
                this.SuspendLayout();
                this.ResumeLayout(false);

            }
        }

}

Answer 1

控件的构造函数在设计时和运行时都运行。因此，只要您将控件放在窗体上，它就会填充树视图。问题是，节点将被序列化为InitializeComponent（）。看看你的表单的Designer.cs文件，你会发现它们在那里。运行表单时，构造函数再次运行，使列表加倍。

您需要阻止构造函数在设计时添加节点。这有点难以做到，您通常使用DesignMode属性，但在构造函数中它尚未设置为true。这样做是这样的：

protected override void OnHandleCreated(EventArgs e) {
    base.OnHandleCreated(e);
    if (!DesignMode && treeView.Nodes.Count == 0) {
        CreateTree(this);
    }
}

或者通过添加在窗体的构造函数或OnLoad方法中调用的公共方法来显式地执行此操作。这是明智的，您可能想要捕获异常。修补文件系统时总是有可能。

什么可能导致这个多次填充这个树视图？

1 个答案: