Windows.Forms DragLeave 事件意外触发

Question

自定义 UserControl ChartControlShelf 包含一个带有 3 个子控件的 TableLayoutPanel，所有类型均为 Panel。孩子没有事件处理程序。

ShelfContainer 为 UserControl ChartControlShelf 添加所有 EventHandlers：

ChartControlShelf chartControlShelf = new ChartControlShelf();
chartControlShelf.DragOver+=new DragEventHandler(chartControlShelf_DragOver);
chartControlShelf.DragLeave+=new EventHandler(chartControlShelf_DragLeave); 

....

private void chartControlShelf_DragOver(object sender, DragEventArgs e) {

        ChartControlShelf chartControlShelf = (ChartControlShelf)sender;

        if (chartControlShelf.panelControlShelf.PointToClient(Cursor.Position).Y < chartControlShelf.tlpChartControlShelf.Size.Height / 2) {
            chartControlShelf.panelInsertTop.BackColor = CustomColorsColors.DragEnter;
            chartControlShelf.panelInsertBottom.BackColor = CustomColorsColors.DragLeave;
        }
        else {
            chartControlShelf.panelInsertBottom.BackColor = CustomColorsColors.DragEnter;
            chartControlShelf.panelInsertTop.BackColor = CustomColorsColors.DragLeave;
        }
   }

    private void chartControlShelf_DragLeave(object sender, EventArgs e) {
        ChartControlShelf chartControlShelf = (ChartControlShelf)sender;
        chartControlShelf.panelInsertTop.BackColor = CustomColorsColors.DragLeave;
        chartControlShelf.panelInsertBottom.BackColor = CustomColorsColors.DragLeave;

    }

为什么*chartControlShelf_DragLeave* 在我的鼠标离开ChartControlShelf UserControl之前触发？

Answer 1

鼠标光标“属于”指针下方直接可见的控件。听起来很奇怪，当光标“进入”ChartControlShelf 中的某个控件时，它也“离开”了 ChartControlSelf。