在WinForm中加控件ListBox1(ListBox)。并有如下代码，当事件ListBox1.SelectedIndexChanged发生， Private Sub ABC()被调用。如果我按住向下键不放，ListBox1.SelectedIndex连续变化，ListBox1.SelectedIndexChanged连续发生，Private Sub ABC()被连续调用。问题：我只要最后一个SelectedIndexChanged事件(松开向下键)或选项滚到底( ListBox1.SelectedIndex = 1000 )的时候，Private Sub ABC()才被调用，中间的SelectedIndexChanged事件不调用Private Sub ABC()。


Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim i As Integer
ListBox1.Items.Clear()
For i = 0 To 1000
ListBox1.Items.Add(i)
Next
ListBox1.SelectedIndex = 0
End Sub

Private Sub ListBox1_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles ListBox1.SelectedIndexChanged
ABC()
End Sub
Private Sub ABC()

End Sub

本文发表在 rolia.net 枫下论坛vb.net会 ，但是用着不习惯，用C#来写。
此题关键是考你event和win form 键盘输入的知识，还是能考出面试者一些功底的，太晚了，明天再作上面2道

// define a bool just to let listbox judge whether to run ABC() or not
private bool DownKeyPressed=false;

private void Form1_Load(object sender, System.EventArgs e)
{
for(int i=1;i<=1000;i++)
this.listBox1.Items.Add(i);
// add the key up and down event to the listbox
this.listBox1.KeyDown+=new KeyEventHandler(OnKeyDown);
this.listBox1.KeyUp+=new KeyEventHandler(OnKeyUp);
}

// the key up handler function
void OnKeyUp(object o, KeyEventArgs e)
{
if(e.KeyCode==Keys.Down)
{
int i=this.listBox1.SelectedIndex;
this.listBox1.SelectedIndex=0;
this.DownKeyPressed=false;
this.listBox1.SelectedIndex=i;
}
}

// the key down handler function
void OnKeyDown(object o,KeyEventArgs e)
{
if(e.KeyCode==Keys.Down)
this.DownKeyPressed=true;
}

private void listBox1_SelectedIndexChanged(object sender, System.EventArgs e)
{
if(this.DownKeyPressed==true && this.listBox1.SelectedIndex<999)
return;
ABC();
}更多精彩文章及讨论，请光临枫下论坛 rolia.net

就是在 validating 函数里加一句判断

private void textBox1_Validating(object sender, System.ComponentModel.CancelEventArgs e)
{
if(this.button2.Focused==true)
{
If (!IsValidated())
e.Cancel = True
}
}