.aspx
--------------------------------
<asp:ListBox id="ListBox1" style="Z-INDEX: 105; LEFT: 96px; POSITION: absolute; TOP: 344px" runat="server">
<asp:ListItem Value="a1">a1</asp:ListItem>
<asp:ListItem Value="a2">a2</asp:ListItem>
<asp:ListItem Value="a3">a3</asp:ListItem>
</asp:ListBox>
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.cs
//for 个
private void Button1_Click(object sender, System.EventArgs e){
if (this.ListBox1.SelectedIndex>=0)
{
int i = ListBox1.SelectedIndex;
if(i>0)
{
string values = this.ListBox1.Items[i].Text ;
this.ListBox1.Items[i].Text = this.ListBox1.Items[i-1].Text ;
this.ListBox1.Items[i-1].Text = values;
}
}
}