c# – 如何循环控件以获取特定类型的控件？

<div id="columns" runat="server">
       <ul id="column1" class="column" >
        <!-- /////////////// -->
        </ul>
        <ul id="column2" class="column" runat="server">
        </ul>
        <ul id="column3" class="column" runat="server">
        </ul>
        <ul id="column4" class="column" runat="server">
            <asp:PlaceHolder ID="PlaceHolder1" runat="server"></asp:PlaceHolder>
        </ul>
    </div>

在运行时创建时listItems(HtmlGenericControl outer_li =新HtmlGenericControl( “里”))在(UL具有属性RUNAT = “服务器”).

现在我想做的是：
通过DIV ID =循环“列”,以获取每个(UL具有属性RUNAT =“服务器”),然后通过每个(UL)循环获得每个列表项保存的内容.

编辑：根据答案：

foreach (Control c in columns.Controls.OfType<HtmlGenericControl>())
        {
            var ctrl = (HtmlGenericControl)c;

            if (ctrl.TagName == "ul" && ctrl.ID != "column1")
            {
                foreach (Control li in ctrl.Controls.OfType<HtmlGenericControl>())
                {

                    var ctrl_li = (HtmlGenericControl)li;
                    if (ctrl_li.TagName == "li")
                    {
                        string id = ctrl_li.ID;
                    }
                }
            }
        }

虽然我的页面上有li,但这根本无法获得’li’

编辑2：

protected void CreateBlockOfData(string widget_color,int column_par,string process_name,int block_type,int block_id)
        {
            HtmlGenericControl outer_li = new HtmlGenericControl("li");
            outer_li.Attributes.Add("class",widget_color);
            if (column_par == 1)
            {
                column1.Controls.Add(outer_li);
            }
            else if (column_par == 2)
            {
                //uppnl_2.ContentTemplateContainer.Controls.Add(outer_li);
                column2.Controls.Add(outer_li);
            }
            else if (column_par == 3)
            {
                column3.Controls.Add(outer_li);
            }
            else if (column_par == 4)
            {
                column4.Controls.Add(outer_li);
            }
            ////////////////////////////////////////////////////////////
            HtmlGenericControl div_head = new HtmlGenericControl("div");
            div_head.Attributes.Add("class","widget-head");
            outer_li.Controls.Add(div_head);
            ////////////////////////////////////////////////////////////
            HtmlGenericControl h3 = new HtmlGenericControl("h3");
            div_head.Controls.Add(h3);
            ///////////////////////////////////////////////////////////
            Label lbl_process_name = new Label();
            lbl_process_name.Text = process_name.TrimEnd();
            h3.Controls.Add(lbl_process_name);
            ///////////////////////////////////////////////////////////
            HtmlGenericControl div_content = new HtmlGenericControl("div");
            div_content.Attributes.Add("class","widget-content");
            outer_li.Controls.Add(div_content);
            ////////////////////////Data//////////////////////////////
            Control crl_data = FormTheData(block_type,block_id);
            PlaceHolder1.Controls.Add(crl_data);
            crl_data.DataBind();
            div_content.Controls.Add(crl_data);
        }