将一个控件拖放到Winform中的另一个控件

Question

我做的事情非常非常简单。

我有一个列表框，其事件设置如下：

    public Form1()
    {
        InitializeComponent();
        this.listBox1.AllowDrop = true;
        this.listBox1.DragEnter += new DragEventHandler(listBox1_DragEnter);
        this.listBox1.DragDrop += new DragEventHandler(listBox1_DragDrop);
    }

    void listBox1_DragDrop(object sender, DragEventArgs e)
    {
       //code to add labelText to Items of ListBox
    }

    void listBox1_DragEnter(object sender, DragEventArgs e)
    {
        //set DragDropEffects;
    }

现在我有一个标签，其代码如下：

    private void label1_MouseDown(object sender, MouseEventArgs e)
    {
        DoDragDrop((sender as Label).Text, DragDropEffects.Copy);
        //this.label1.DoDragDrop((sender as Label).Text, DragDropEffects.Copy);
        //used one of them at a time.

    }

但什么也没发生。 列表框DragEnter事件从不触发。 实际上，拖曳永远不会发生。 每当我尝试拖动标签（文本）时，出现不允许的Windows光标，而不是' DragDropEffects.Copy的光标

拖放不会发生。

当我修改列表框（及其关联的代码）以接受要从任何其他窗口拖放到其上的文件时，效果很好。

so..am无法执行从窗体上保留的控件到同一窗体上另一个控件的拖动。

我错过了什么吗？ 正在运行Windows XP。

我经历了这个 ，并通过这种

请帮忙...

Answer 1

您的代码确实可以正常工作。 您只需要在事件处理程序中设置正确的拖动效果即可。

void listBox1_DragDrop(object sender, DragEventArgs e)
{
  e.Effect = DragDropEffects.Copy;
}

void listBox1_DragEnter(object sender, DragEventArgs e)
{
  e.Effect = DragDropEffects.Copy;
}

Answer 2

检查ListBox.AllowDrop是否设置为TRUE

Answer 3

以下是所有代码的示例（将其添加到此处的人员）。

#region Initial Values
//Constructor:
public Form1() {
   InitializeComponent();
}

private void Form1_Load( object sender, EventArgs e ) {
   InitialValues();
}

private void InitialValues() {
   PrepareDragAndDrop();
}
#endregion Initial Values

#region Drag & Drop

private void PrepareDragAndDrop() {
   //For the object that receives the other dragged element:
   TheSamplListBox.AllowDrop = true;
   TheSamplListBox.DragEnter += TheSamplListBox_DragEnter;
   TheSamplListBox.DragLeave += TheSamplListBox_DragLeave;
   TheSamplListBox.DragDrop  += TheSamplListBox_DragDrop;

   //For the object that will be dragged:
   TheSampleLabel.MouseDown += ( sender, args ) => DoDragDrop( TheSampleLabel.Text, DragDropEffects.Copy );
}

private void TheSamplListBox_DragEnter( object theReceiver, DragEventArgs theEventData ) {
   theEventData.Effect = DragDropEffects.Copy;

   //Only the code above is strictly for the Drag & Drop. The following is for user feedback:
   //You can use [TheSamplListBox] but this approach allows for multiple receivers of the same type:
   var theReceiverListBox = (ListBox) theReceiver;

   theReceiverListBox.BackColor = Color.LightSteelBlue;
}

private void TheSamplListBox_DragLeave( object theReceiver, EventArgs theEventData ) {
   //No code here for the Drag & Drop. The following is for user feedback:
   //You can use [TheSamplListBox] but this approach allows for multiple receivers of the same type:
   var theReceiverListBox = (ListBox) theReceiver;

   theReceiverListBox.BackColor = Color.White;
}

private void TheSamplListBox_DragDrop( object theReceiver, DragEventArgs theEventData ) {
   //You can use [TheSamplListBox] but this approach allows for multiple receivers of the same type:
   var theReceiverListBox = (ListBox) theReceiver;

   //Get the data being dropped. In this case, a string:
   var theStringBeingDropped = theEventData.Data.GetData( "System.String" );

   //Add the string to the ListBox:
   theReceiverListBox.Items.Add( theStringBeingDropped );

   //Only the code above is strictly for the Drag & Drop. The following is for user feedback:
   theReceiverListBox.BackColor = Color.White;
}
#endregion Drag & Drop

。