c#中禁用当鼠标位于控件上方时ToolStripDropDownButton上的蓝色焦点

重写toolStrip1.Renderer的属性然后重新赋值

using System;
using System.Windows.Forms;
using System.Drawing;
namespace WindowsFormsApplication1
{
   public partial class Form1 : Form
   {
       public Form1()
       {
           InitializeComponent();
toolStrip1.BackColor = Color.Transparent;
           toolStrip1.GripStyle = ToolStripGripStyle.Visible;
           toolStrip1.Renderer = new MyRenderer();
       }
private class MyRenderer : ToolStripSystemRenderer
       {
          protected override void OnRenderArrow(ToolStripArrowRenderEventArgs e)
          {
              e.ArrowColor = Color.White;
              base.OnRenderArrow(e);
          }
protected override void OnRenderToolStripBorder(ToolStripRenderEventArgs e)
          {
             // remove white line bellow button (http://connect.microsoft.com/VisualStudio/feedback/details/92862/toolstrip-always-draws-a-border-on-the-bottom-with-rendermode-system-and-docked-left-or-right)
             //base.OnRenderToolStripBorder(e);
          }
       }
    }
}