在winform中将一个控件拖放到另一个控件答案

【问题标题】：Drag and Drop one control to another control in winform在winform中将一个控件拖放到另一个控件
【发布时间】：2012-07-23 17:46:06
【问题描述】：

我正在做一些非常非常简单的事情。

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;
    }

现在我有了一个标签，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 事件永远不会触发。事实上，阻力永远不会发生。每当我尝试拖动标签（文本）时，出现不允许的窗口光标，而不是'DragDropEffects.Copy's cursor

拖放不会发生..

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

所以..我无法从表单上的控件拖动到同一表单上的另一个控件。

我错过了什么吗？我正在运行 Windows XP。

我经历了this和this

请帮忙...

【问题讨论】：

标签： c# winforms drag-and-drop

【解决方案1】：

您的代码确实有效。您只需在事件处理程序中设置正确的拖动效果。

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

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

【讨论】：

【解决方案2】：

检查 ListBox.AllowDrop 是否设置为 TRUE

【讨论】：

它在构造函数this.listBox1.AllowDrop = true;

【解决方案3】：

以下是您需要的示例，以及所有代码（将其添加到此处以供找到此帖子的人使用）。

#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

【讨论】：