C＃ListView DragDrop事件方法每次执行两次

Question

The method executes twice in a row and there's no apparent reason for doing so. It happens in VS2010 Express (4.0) and in VS2008 (3.5).

public GUI()
{
    InitializeComponent();
    this.lvwFiles.DragDrop += new System.Windows.Forms.DragEventHandler(this.lvwFiles_DragDrop);
    this.lvwFiles.DragEnter += new System.Windows.Forms.DragEventHandler(this.lvwFiles_DragEnter);
}  
private void lvwFilesAdd(string path, string[] paths)
{ ... }  
private void lvwFilesWrite()
{ ... }  
private void lvwFiles_DragEnter(object sender, DragEventArgs e)
{
    if (e.Data.GetDataPresent(DataFormats.FileDrop))
        e.Effect = DragDropEffects.Copy;
    else
        e.Effect = DragDropEffects.None;
}  
private void lvwFiles_DragDrop(object sender, DragEventArgs e)
{
    if (e.Data.GetDataPresent(DataFormats.FileDrop))
    {
        var paths = (string[])e.Data.GetData(DataFormats.FileDrop);
        var path = Path.GetDirectoryName(paths[0]);
        lvwFilesAdd(path, paths);
        lvwFilesWrite();
    }
}

Answer 1

I was following Microsoft example and didn't notice that the declarations in GUI.Designer.cs (automatic, by IDE) and in GUI.cs (manual, from example) are redundant.

=== GUI.cs ===
public GUI()
{
    InitializeComponent();
    this.lvwFiles.DragDrop += new System.Windows.Forms.DragEventHandler(this.lvwFiles_DragDrop);
    this.lvwFiles.DragEnter += new System.Windows.Forms.DragEventHandler(this.lvwFiles_DragEnter);
}

=== GUI.Designer.cs ===
// 
// lvwFiles
//
... 
this.lvwFiles.DragDrop += new System.Windows.Forms.DragEventHandler(this.lvwFiles_DragDrop);
this.lvwFiles.DragEnter += new System.Windows.Forms.DragEventHandler(this.lvwFiles_DragEnter);