说明：FlowLayoutPanel里边放入Label，对Label拖拽实现排序。

1.给Label注册MouseDown事件：

label.MouseDown += new System.Windows.Forms.MouseEventHandler(Label_MouseDown);

响应Label鼠标按下事件内容：11

private void Label_MouseDown(object sender, MouseEventArgs e)
{                                                         
    if (e.Button == MouseButtons.Left && e.Clicks == 1)   
    {                                                     
        base.OnMouseDown(e);                              
        Label label = sender as Label;                    
        label.DoDragDrop(label, DragDropEffects.All);     
    }                                                     
}                                                   

说明：上边过滤了鼠标左键单击

2.设置FlowLayoutPanel.AllowDrop = true;

3.给FlowLayoutPanel注册DragEnter和DragDrop事件，响应代码如下：

private void FlowLayoutPanel_DragEnter(object sender, DragEventArgs e)   
{                                                                     
    e.Effect = DragDropEffects.All;                                   
}                                                                     
                                                                                                                                                                                                                                                                                   
private void FlowLayoutPanel_DragDrop(object sender, DragEventArgs e)    
{                                                                     
    Label label = (Label)e.Data.GetData(typeof(Label));               
                                                                                                                                                                                                                                                                                   
    Point point = FlowLayoutPanel.PointToClient(new Point(e.X, e.Y));    
    Control control = FlowLayoutPanel.GetChildAtPoint(point);            
    if (control != null && label != control)                          
    {                                                                 
        IsXuHaoChange = true;                                         
        int index = FlowLayoutPanel.Controls.GetChildIndex(control, false);
        FlowLayoutPanel.Controls.SetChildIndex(label, index);            
        FlowLayoutPanel.Invalidate();                                    
    }                                                                 
}

这样，FlowLayoutPanel里边的Label子控件即可通过拖拽排序，排序方法是把拖拽的Label拖拽到要替换的Label上，其他Label完后移位。