c# - 如何在 asp.net 中对 GridView 中的对象列表进行排序？

Question

我有一个对象列表

List<News> theNews = controlClass.ListNews();

ListNews() 加载了数据集中的新闻对象。

然后我有一个gridview

    <asp:GridView ID="gvNews" runat="server" AutoGenerateColumns="False"  OnSelectedIndexChanged="gvNews_SelectedIndexChanged" AllowSorting="True" OnSorting="gvNews_Sorted">
        <Columns>
            <asp:BoundField DataField="titNew" HeaderText="Title" />
            <asp:BoundField DataField="dateNew" HeaderText="Date" SortExpression="dateNew" />
            <asp:BoundField DataField="typeNew" HeaderText="Type" />
            <asp:CommandField SelectText="See More" ShowSelectButton="True" />
        </Columns>
    </asp:GridView>

我将所述列表存储到此 GridView 中，然后我使用以下代码对其进行排序

    private void LoadNews()
    {
        this.gvNews.DataSource = controlClass.ListNews();
        this.gvNews.DataBind();
        ViewState["dt"] = controlClass.ListNews();
        ViewState["sort"] = "Asc";
    }

    protected void gvNews_Sorted(object sender, GridViewSortEventArgs e)
    {
        DataTable result = (DataTable)ViewState["dt"];
        if (result.Rows.Count>0)
        {
            if(ViewState["sort"].ToString()=="Asc")
            {
                result.DefaultView.Sort = e.SortExpression + " Desc";
                ViewState["sort"] = "Desc";
            }
            else
            {
                result.DefaultView.Sort = e.SortExpression + " Asc";
                ViewState["sort"] = "Asc";
            }
            gvNews.DataSource = result;
            gvNews.DataBind();
        }
    }

但这导致我出现以下错误: 在程序集“MySolution，Version=1.0.0.0，Culture=neutral，PublicKeyToken=null”中键入“MySolution.News”未标记为可序列化。我似乎无法将我的列表存储在 ViewState 中，有解决办法吗？

更新:我已经使我的新闻类可序列化，但是当我单击 GridView 中的日期标题时出现以下错误

无法将“System.Collections.Generic.List`1[MySolution.News]”类型的对象转换为类型“System.Data.DataTable”。

更新编号 2:我修改了我的 gvNews_Sorted 方法以匹配@Dr.Stitch 的答案。

protected void gvNews_Sorted(object sender, GridViewSortEventArgs e)
{
   List<News>result = (List<News>)ViewState["dt"];
   if (result.Count>0)
   {
      if(ViewState["sort"].ToString()=="Asc")
      {
        result = result.OrderBy(e.SortExpression + " Desc").ToList();
        ViewState["sort"] = "Desc";
      }
      else
      {
         result = result.OrderBy(e.SortExpression + " Asc").ToList();
         ViewState["sort"] = "Asc";
      }

      gvNews.DataSource = result;
      gvNews.DataBind();
   }
}

我在行中收到以下错误

result = result.OrderBy(e.SortExpression + " Desc").ToList();

更新 3: 我在尝试 Dr Stitch 的新答案时做了进一步的更改，现在尽管不再崩溃，但它什么也没做，当我点击标题时没有任何变化

Answer 1

您正在保存 List<News>对象

ViewState["dt"] = controlClass.ListNews();

但试图检索 DataTable对象

DataTable result = (DataTable)ViewState["dt"];

你必须改变你的gvNews_Sorted对此:

protected void gvNews_Sorted(object sender, GridViewSortEventArgs e)
{
   List<News>result = (List<News>)ViewState["dt"];
   if (result.Count>0)
   {
      if(ViewState["sort"].ToString()=="Asc")
      {
        if ("titNew" == e.SortExpression)
            result = result.OrderByDescending(r => r.titNew).ToList();
        //...do it to all the fields

        ViewState["sort"] = "Desc";
      }
      else
      {
        if ("titNew" == e.SortExpression)
            result = result.OrderBy(r => r.titNew).ToList();
        //...do it to all the fields
         ViewState["sort"] = "Asc";
      }

      gvNews.DataSource = result;
      gvNews.DataBind();
      ViewState["dt"] = result;
   }
}

确保 LoadNews()仅调用非回发事件

protected void Page_Load(object sender, EventArgs e)
{
  if (!IsPostBack)
  {
     LoadNews();
  }
}