private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
s = s + "SelectedIndexChanged = " + comboBox1.Text + "\r\n";
BeginInvoke(new EventHandler(InvokeAfter), sender, e);
}
void InvokeAfter(object sender, EventArgs e)
{
comboBox1.Text = (t + "," + comboBox1.Text).TrimStart(','); //原内容与新内容合并显示}
试试SelectionChangeCommitted事件