HyperLink控件產生System.NullReferenceException

Question

我知道這是一個一直被毆打的死馬，但我需要一些協助解決「System.NullReferenceException：對象引用未設置爲對象實例」。問題。我已經去了很多的鏈接，但我是編程新手，我不能從這些建議的尾巴開始。

錯誤發生在第47行：

Line 45: HyperLink topNavigation = (HyperLink)e.Item.FindControl("HyperLinkTopNavigation"); 
Line 46: //Use Sitecore API to get the link to the Item and upadte the href property of link 
Line 47: topNavigation.NavigateUrl = LinkManager.GetItemUrl(currentItem); 
Line 48: //Assign name to the link 
Line 49: topNavigation.Text = currentItem.Name; 

---

我的ascx代碼：

後面的代碼

<%@ Control Language="c#" AutoEventWireup="true" TargetSchema="http://schemas.microsoft.com/intellisense/ie5" Inherits="Layouts.Topnavigation.TopnavigationSublayout" CodeFile="~/layouts/TopNavigation.ascx.cs" Debug="true" %> 

<%@ register TagPrefix="sc" Namespace="Sitecore.Web.UI.WebControls" Assembly="Sitecore.Kernel" %> 
    <asp:repeater runat="server" id="RepeaterTopNavigation" onitemdatabound="RepeaterTopNavigation_ItemDataBound"> 
<headertemplate> 
<ul> 
<li><a href="home.aspx">Home</a></li> 


<itemtemplate> 
<li> 
<asp:hyperlink id="HyperLinkTopNavigation" runat="server"></asp:hyperlink> 
</li> 
</itemtemplate> 

<footertemplate> 

</footertemplate></ul></headertemplate> 
</asp:repeater>  

我的是：

using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Web; 
using System.Web.UI; 
using System.Web.UI.WebControls; 
using Sitecore.Data.Items; 
using Sitecore.Links; 


namespace Layouts.Topnavigation { 

    /// <summary> 
    /// Summary description for TopnavigationSublayout 
    /// </summary> 
    public partial class TopnavigationSublayout : System.Web.UI.UserControl 
{ 
      protected void Page_Load(object sender, EventArgs e) 
{ 
//get the home item, this is hardcoded but you can define it in web.config 
Item home = Sitecore.Context.Database.GetItem("/sitecore/content/home"); 
//get all children from home using Sitecore API 
Item[] children = home.Children.ToArray(); 
//Bind the children to repeater 
RepeaterTopNavigation.DataSource = children; 
RepeaterTopNavigation.DataBind(); 

} 

public void RepeaterTopNavigation_ItemDataBound(object sender, RepeaterItemEventArgs e) 
{ 
//gets the current data item from RepeaterItemEventsArgs and cast it as a Sitecore Item 
Item currentItem = (Item)e.Item.DataItem; 

//check if it is not null, safety first 
if (currentItem != null) 
{ 

//check if it is coming from Item or Alternating Item template 
if (e.Item.ItemType == ListItemType.Item || 
      e.Item.ItemType == ListItemType.AlternatingItem) 
{ 

//Find the HyperLink control that has been defined in repeater 
HyperLink topNavigation = (HyperLink)e.Item.FindControl("HyperLinkTopNavigation"); 
//Use Sitecore API to get the link to the Item and upadte the href property of link 
topNavigation.NavigateUrl = LinkManager.GetItemUrl(currentItem); 
//Assign name to the link 
topNavigation.Text = currentItem.Name; 

} 
} 
} 
} 
} 

Answer 1

你headertemplate標籤包裝整個中繼器，這是可能爲什麼沒有找到HyperLink控件。像這樣修復：

<asp:repeater runat="server" id="RepeaterTopNavigation" onitemdatabound="RepeaterTopNavigation_ItemDataBound"> 
<headertemplate> 
<ul> 
<li><a href="home.aspx">Home</a></li> 
</headertemplate> 
<itemtemplate> 
<li> 
<asp:hyperlink id="HyperLinkTopNavigation" runat="server"></asp:hyperlink> 
</li> 
</itemtemplate> 

<footertemplate> 
</ul> 
</footertemplate> 
</asp:repeater>