看起来对sourceListBox.SelectionMode = SelectionMode.MultiExtended;的调用正在重置TopIndex。在该调用 * 之后 * 设置TopIndex将起作用：

private void textBox1_TextChanged(object sender, EventArgs e)
{
    int topIndex = sourceListBox.TopIndex;

    sourceListBox.SelectionMode = SelectionMode.One;
    if (textBox1.Text != string.Empty)
    {
        int index = sourceListBox.FindString(textBox1.Text);
        if (index != -1 && sourceListBox.SelectedIndex != index)
        {
            sourceListBox.ClearSelected();
            sourceListBox.SetSelected(index, true);
            topIndex = sourceListBox.SelectedIndex;
        }
    }
    else
    {
        sourceListBox.ClearSelected();
    }

    sourceListBox.SelectionMode = SelectionMode.MultiExtended;
    sourceListBox.TopIndex = topIndex;
}

如果当前SelectedIndex等于FindString的结果，则删除对当前SelectedIndex的检查，设置TopIndex的代码将始终执行

private void textBox1_TextChanged(object sender, EventArgs e)
{
        .....
        int index = sourceListBox.FindString(textBox1.Text);
        if (index != -1)
        {
            sourceListBox.ClearSelected();
            sourceListBox.SetSelected(index, true);
            sourceListBox.TopIndex = sourceListBox.SelectedIndex;
        }
        ....
}

变更

sourceListBox.TopIndex = sourceListBox.SelectedIndex;

至

sourceListBox.TopIndex = index;

到winforms列表框

SendMessage(listBox.Handle,LB_SETTOPINDEX, 0, 0);

将使最上面的项目可见，保证，而不改变其选择状态，这可以是一个很好的触摸时，刚刚启动一个应用程序和反序列化加载一个列表框。