<p>如果重复单击GridView 的列标题,排序顺序就会在升序和降序之间来回切换。GridView的Sort方法还可以接受多个SortExpression,进行多列排序。这需要在后台的代码文件中添加如下代码:</p>
    protected void GridView1_Sorting(object sender, GridViewSortEventArgs e)
    {
        string oldExpression = GridView1.SortExpression;
        string newExpression = e.SortExpression;
        if (oldExpression.IndexOf(newExpression) < 0)
        {
            if (oldExpression.Length > 0)
                e.SortExpression = newExpression + "," + oldExpression;
            else
                e.SortExpression = newExpression;
        }
        else
        {
            e.SortExpression = oldExpression;
        }
    }