this.listBox1.SelectedIndexChanged -= new EventHandler(listBox1_SelectedIndexChanged);
this.listBox1.SetSelected(..., ...);
// 这样 SetSelected 就不触发事件，在这里执行些别的代码
this.listBox1.SelectedIndexChanged += new EventHandler(listBox1_SelectedIndexChanged);

------解决方案--------------------

C# code

// 调用 SetSelected 的代码
this.listBox1.SelectedIndexChanged -= new EventHandler(listBox1_SelectedIndexChanged);
this.listBox1.SetSelected(..., ...);// 在这执行 SetSelected
this.listBox1_SelectedIndexChanged(null, null); // 直接调用事件方法，等同于触发
this.listBox1.SelectedIndexChanged += new EventHandler(listBox1_SelectedIndexChanged);

// 事件方法
private void listBox1_SelectedIndexChanged(object sender, EventArgs e)
{
    if (sender == null)
    {
        // 是 SetSelected 触发的
    }
    else
    {
        // 是别的触发的
    }
}

------解决方案--------------------
listBox1_SelectedIndexChanged(object sender, EventArgs e)
时间里面判断键盘鼠标事件，是否是键盘和鼠标触发的，，第三种是代码触发的很好区分