查找控制在Datalist中

Question

當我試圖找到控制n個數據列表，我下面提到

Error(Object reference not set to an instance of an object. 

我不知道

protected void dlCategory_ItemDataBound(object sender, DataListItemEventArgs e) 
    { 
     Label Lb = (Label)e.Item.FindControl("LblCat"); 
     Lb.ForeColor = System.Drawing.Color.Red; 
    } 



<Datalist> 
<asp:DataList ID="dlSubCategory" runat="server" 
            DataSource='<%# GetSubCategory(Convert.ToString(Eval("Category_ID")))%>' 
            onitemcreated="dlSubCategory_ItemCreated" 
            onitemdatabound="dlSubCategory_ItemDataBound"> 
            <EditItemStyle ForeColor="#CC3300" /> 
            <SelectedItemStyle ForeColor="#CC3300" /> 
            <ItemTemplate> 
             <div class="buttn_div_sub"> 
              <div class="lm40 tm2 buttn_txt"> 
               <a href='<%# Convert.ToString(Eval("ProductCategory_Id")).Insert(0,"ListView.aspx?ProductCategory_Id=") %>' 
                class="buttn_txt"> 
                <asp:Label ID="Label1" runat="server" Text='<%#DataBinder.Eval(Container.DataItem,"Name") %>'></asp:Label> 
               </a> 
              </div> 
             </div> 
            </ItemTemplate> 
           </asp:DataList> 
          </ItemTemplate> 

Answer 1

protected void dlCategory_ItemDataBound(object sender, DataListItemEventArgs e) 
{ 
    Label Label1 = e.Item.FindControl("Label1") as Label; 
    if (LblCat != null) 
    { 
     string id = ((System.Data.DataRowView)e.Item.DataItem).Row["ProductCategory_Id"].ToString(); 

     if (Request.QueryString["ProductCategory_Id"] == id) 
     { 
      Label1.ForeColor = System.Drawing.Color.Red; 
     } 
    } 
} 

Answer 2

你能試試嗎？傳遞給這個函數的第一項是頭（如果存在於datalist上），這就是爲什麼你會得到錯誤。

protected void dlCategory_ItemDataBound(object sender, DataListItemEventArgs e) 
{ 
    if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem) 
    { 
     Label Lb = (Label)e.Item.FindControl("LblCat"); Lb.ForeColor = System.Drawing.Color.Red; 
    } 
}