如何在WinForm中触发事件时添加控件？

Question

我喜欢在form1中添加控件，其中一个事件处理程序为 watcher.Changed + = new FileSystemEventHandler（OnChanged）;定义，是有可能例如列表框控件添加到Form1，但需要定义它

/*event added*/ 

    private void btn_start_Click(object sender, EventArgs e) 
    { 
     string[] args = {this.txtfolder.Text}; 
     if (args.Length != 1) 
     { 
      // Display the proper way to call the program. 
      Console.WriteLine("Usage: Invalid Operation"); 
      return; 
     } 

     FileSystemWatcher watcher = new FileSystemWatcher(); 
     watcher.Path = args[0]; 
     /* Watch for changes in LastAccess and LastWrite times, and 
      the renaming of files or directories. */ 
     watcher.NotifyFilter = NotifyFilters.LastAccess | NotifyFilters.LastWrite 
      | NotifyFilters.FileName | NotifyFilters.DirectoryName; 
     // Only watch text files. 
     watcher.Filter = this.txtfilter.Text;//"*.txt"; 

     // Add event handlers. 
     watcher.Changed += new FileSystemEventHandler(OnChanged); 
     watcher.Created += new FileSystemEventHandler(OnChanged); 
     // watcher.Deleted += new FileSystemEventHandler(OnChanged); 
     watcher.Renamed += new RenamedEventHandler(OnRenamed); 



    // Define the event handlers. 
    private static void OnChanged(object source, FileSystemEventArgs e) 
    { 
     // Specify what is done when a file is changed, created, or deleted. 
     //Console.WriteLine("File: " + e.FullPath + " " + e.ChangeType); 

     // Form1 F ;   
     // ListBox lst = new ListBox(); 
     //lst.Items.Add("File: " + e.FullPath + " " + e.ChangeType.ToString()); 
     //f.lsttracker.Items.Add("File: " + e.FullPath + " " + e.ChangeType.ToString()); 
     // F.controls.Add(lst); 

Answer 1

这是你找什么事件处理中被添加。从您注释的内容来看，您可能没有设置位置和大小，因此添加控件可能不起作用。但是你应该确保调整这一点，并确保你只是在你想要的时候才加入控件，而不是更多。

private static void OnChanged(object source, FileSystemEventArgs e) 
{ 
    ListBox toAdd = new ListBox(); 
    toAdd.Location = new Point(20,20); 
    toAdd.Size = new Size(200,200); 
    this.Controls.Add(toAdd); 
} 

如果你想保存你添加的控件，尝试这样的事情：

private List<Control> AddedItems = new List<Controls>(); 
private int OffsetY = 0; 
private static void OnChanged(object source, FileSystemEventArgs e) 
{ 
    ListBox toAdd = new ListBox(); 
    if(AddedItem.Last().Point.Y == OffsetY) // just an example of reusing previously added items. 
    { 
     toAdd.Location = new Point(20, OffsetY); 
     toAdd.Size = new Size(200,200); 
     AddedItems.Add(toAdd); 
     this.Controls.Add(toAdd); 
    } 
    OffsetY += 200; 
} 

编辑：在回答你在下面的评论中提到的内容。

[PermissionSet(SecurityAction.Demand, Name = "FullTrust")] 
    private void btn_start_Click(object sender, EventArgs e) 
    { 
     string FolderPath = this.txtfolder.Text; 
     string Filter = this.txtfilter.Text; 
     if(!Directory.Exists(FolderPath)) 
     { 
      Console.WriteLine("Not a valid directory"); //checks directory is valid 
      return; 
     } 

     FileSystemWatcher watcher = new FileSystemWatcher(); 

     watcher.Path = FolderPath; 
     watcher.NotifyFilter = NotifyFilters.LastAccess | NotifyFilters.LastWrite 
           | NotifyFilters.FileName | NotifyFilters.DirectoryName; 
     // Only watch filter files. 
     watcher.Filter = Filter; 

     watcher.IncludeSubdirectories = true; //monitor subdirectories? 
     watcher.EnableRaisingEvents = true; //allows for changed events to be fired. 

     // Add event handlers. 
     watcher.Changed += new FileSystemEventHandler(OnChanged); 
     watcher.Created += new FileSystemEventHandler(OnChanged); 
    } 
    //Delegate to get back to UI thread since OnChanged fires on non-UI thread. 
    private delegate void updateListbox(string context); 
    private void OnChanged(object source, FileSystemEventArgs e) 
    { 
     this.Invoke(new updateListbox(UpdateListbox), "File: " + e.Name); 
     this.Invoke(new updateListbox(UpdateListbox), ">>Action: " + e.ChangeType); 
     this.Invoke(new updateListbox(UpdateListbox), ">>Path: " + e.FullPath); 
    } 
    public void UpdateListbox(string context) 
    { 
     lsttracker.Items.Add(context); 
    }