跨 MDI 子窗体的拖放操作
我正在尝试执行一个简单的拖放操作，从一个 MDI 子窗体中的一个按钮开始到另一个 MDI 子窗体中的另一个按钮。然而，由于某种原因，当我尝试将一个按钮拖动到另一个按钮时，DragDrop 事件永远不会被触发。值得注意的是，当我拖动按钮时，我的光标变成黑色取消图标。
我的代码：
#region ActivatesDragDropControl
[DllImport ("user32.dll")]
public static extern int SendMessage(IntPtr hWnd, int Msg, int wParam, int lParam);
private const int WM_NCACTIVATE = 0x0086;
#endregion
private void button1_MouseDown(object sender, MouseEventArgs e)
{
DoDragDrop(LocationNode, DragDropEffects.Link);
// to deactivate
SendMessage(Handle, WM_NCACTIVATE, 0, 0);
}
private void button1_DragDrop(object sender, DragEventArgs e)
{
//never gets here...
}
private void button1_DragEnter(object sender, DragEventArgs e)
{
// to activate
SendMessage(Handle, WM_NCACTIVATE, 1, 0);
}
I am trying to perform a simple drag-n-drop operation starting from one button in one MDI child form to another button in a different MDI child form. For some reason however the DragDrop event never gets fired when I attempt to drag one button to the other. It may be worth noting that when I drag the button my cursor becomes the black-cancel icon.
My code:
#region ActivatesDragDropControl
[DllImport ("user32.dll")]
public static extern int SendMessage(IntPtr hWnd, int Msg, int wParam, int lParam);
private const int WM_NCACTIVATE = 0x0086;
#endregion
private void button1_MouseDown(object sender, MouseEventArgs e)
{
DoDragDrop(LocationNode, DragDropEffects.Link);
// to deactivate
SendMessage(Handle, WM_NCACTIVATE, 0, 0);
}
private void button1_DragDrop(object sender, DragEventArgs e)
{
//never gets here...
}
private void button1_DragEnter(object sender, DragEventArgs e)
{
// to activate
SendMessage(Handle, WM_NCACTIVATE, 1, 0);
}
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评论（1）
好吧，我又玩了一下，使用 DragEnter 还不够；我必须设置 DragEventArgs 的事件值。就我而言：
OK so I played around a bit more and using DragEnter isn't enough; I had to set the DragEventArgs' Event value. In my case: