C# 如何引用多列列表中的列<&燃气轮机；并在FindControl中使用列值

FindControl正在引发空引用异常。我必须引用一个包含 控件id要在页中匹配，但使用包含 控件的名称。我试图创建一个结构，但仍然抛出异常。我知道我想做什么，以及如何做。有人能帮忙吗

我尝试了许多FindControl的变体，但它只适用于direct 对div id（FirstName）的引用请参见我的代码。我把每件事都注释掉了 但此时正在引发异常的FindControl

<div class="form-group" visible="false" id="FirstName" runat="server">
                  <div class="col-xs-12 col-md-8 col-sm-10 nill">
                    <asp:Label ID="lblFirstName" runat="server" AssociatedControlID="txtFirstName" Text="First name *" CssClass="control-label" />
                      <br />
                    <asp:TextBox ID="txtFirstName" runat="server" CssClass="form-control" MaxLength="50" aria-label="First name" required="required" AutoPostBack="true"></asp:TextBox>
                    <span class="required"></span>
                  </div>
                </div>
                     <br />
                </td>
            <td>
//////////////////////////////////////
struct providerList {
                    public int fieldId;
                   public string fieldRequired;
                   public string aspName;
                   public string aspType;
                           }
private void loadform(List<ProviderInRequest> providerList)
        {

            for (int i = 0; i < providerList.Count; i++)


            {


                Control ctrl = FindControl(aspName);  // does not work here I am trying to use column aspName value throws null reference exception  


            }
            //TextBox txt = (TextBox)Page.FindControl(aspName);

            // Target Div tag for plan
            /*  Control ctrl = Page.FindControl("div" + aspName);

              // set visible to true if we found it.
              if(ctrl != null)
              {
                  //set div to visible
                  ctrl.Visible = true;

                  // set label to proper text
                  Label lbl = (Label)Page.FindControl("lbl" + aspName);
                  lbl.Text = displayName;

                  // set required for each input.
                  switch (aspType)
                  {
                      case "txt":
                          TextBox txt = (TextBox)Page.FindControl("txt" + aspName);
                          if(fieldRequired){
                              txt.Attributes.Add("required","required");
                          }
                          else{
                              txt.Attributes.Remove("required");
                          }
                          break;

                          case "ddl":
                          DropDownList ddl = (DropDownList)Page.FindControl("ddl" + aspName);
                          if(fieldRequired){
                              ddl.Attributes.Add("required","required");
                          }
                          else{
                              ddl.Attributes.Remove("required");
                          }
                          break;

*/

//////////////////////////////////////
结构提供程序列表{
公共int字段ID；
需要公共字符串字段；
公共字符串名称；
公共字符串类型；
}
专用无效加载表单（列表提供程序列表）
{
for（int i=0；i