我正在处理用户表单,我希望根据用户需要(在按钮单击事件上)动态生成尽可能多的辅助手机字段。我已经按照此页面上Daniel的动态控制实例:How can I re-instantiate dynamic ASP.NET user controls without using a database?动态ascx用户控件的空引用异常
我也实现了这个网页上提出lordscarlet“事件冒泡”的解决方案:Eventhandling in ascx usercontrols
我user.aspx页面的相关部分:
<asp:Panel ID="phonePnl" runat="server"></asp:Panel>
<tr><td><asp:Button ID="phoneBtn" Text="Add Secondary Phone" OnClick="phoneBtn_Click" runat="server" /></td></tr>
user.aspx.cs的相关部分代码隐藏
// ============================================================================
protected void phoneBtn_Click(object sender, EventArgs e)
{
UserControl controlToAdd = new UserControl();
controlToAdd = (UserControl)controlToAdd.LoadControl("~/DynamicData/FieldTemplates/SecondaryPhone.ascx");
controlToAdd.ID = Guid.NewGuid().ToString();
Panel phonePnl = (Panel)fvUser.FindControl("phonePnl");
Literal lit = new Literal();
lit.Text = "<tr><td>Secondary Phone</td><td>";
phonePnl.Controls.Add(lit);
phonePnl.Controls.Add(controlToAdd);
lit = new Literal();
lit.Text = "</td></tr>";
phonePnl.Controls.Add(lit);
myControlList.Add(controlToAdd.ID, controlToAdd.AppRelativeVirtualPath);
Session["myControlList"] = myControlList;
}
// ============================================================================
protected override void OnInit(EventArgs e)
{
InitializeComponent();
if (!IsPostBack)
{
myControlList = new Dictionary<string, string>();
Session["myControlList"] = myControlList;
}
else
{
myControlList = (Dictionary<string, string>)Session["myControlList"];
foreach (var registeredControlId in myControlList.Keys)
{
UserControl controlToAdd = new UserControl();
controlToAdd = (UserControl)controlToAdd.LoadControl(myControlList[registeredControlId]);
Panel phonePnl = new Panel();
phonePnl = (Panel)fvUser.FindControl("phonePnl");
phonePnl.Controls.Add(controlToAdd);
}
}
base.OnInit(e);
}
// ============================================================================
private void InitializeComponent()
{
this.Load += new System.EventHandler(this.Page_Load);
SecondaryPhoneControl.BubbleClick += new EventHandler(admin_user_BubbleClick);
}
// ============================================================================
private void admin_user_BubbleClick(object sender, EventArgs e)
{
//todo
}
请注意,我添加了最后一行:
Session [“myControlList”] = myControlList;
另外,fvUser只是我在user.aspx页面中的FormView ID。
虽然这不是Daniel的解决方案,但我的想法是,对于您添加的每个控件,都需要将其添加到您的Dictionary中。我完全误导了吗?
我的用户控件是带有TextBox和Button的ascx(用于删除控件,如果用户决定不需要该字段)。请注意,此删除操作尚未实现,但在解决此问题后,该事件在我的父代码中。
SecondaryPhone.ascx
<%@ Control Language="C#" CodeBehind="SecondaryPhone.ascx.cs" Inherits="TwentyFourSeven.DynamicData.FieldTemplates.SecondaryPhone" %>
SecondaryPhone.ascx.cs
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Collections.Specialized;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Xml.Linq;
using System.Web.DynamicData;
namespace TwentyFourSeven.DynamicData.FieldTemplates
{
public partial class SecondaryPhone : System.Web.UI.UserControl
{
protected void Page_Load(object sender, EventArgs e)
{
}
public void SetPhone(String phone)
{
secPhoneTxt.Text = phone;
}
protected override void LoadViewState(object savedState)
{
base.LoadViewState(savedState);
secPhoneTxt.Text = (String)ViewState["secPhoneTxt"];
}
protected override object SaveViewState()
{
ViewState["secPhoneTxt"] = secPhoneTxt.Text;
return base.SaveViewState();
}
private void secPhoneBtn_Click(object sender, EventArgs e)
{
}
public event EventHandler BubbleClick;
protected void OnBubbleClick(EventArgs e)
{
if (BubbleClick != null)
{
BubbleClick(this, e);
}
}
protected override void OnInit(EventArgs e)
{
InitializeComponent();
base.OnInit(e);
}
private void InitializeComponent()
{
this.secPhoneBtn.Click += new System.EventHandler(this.secPhoneBtn_Click);
this.Load += new System.EventHandler(this.Page_Load);
}
}
}
调试时,第一次加载页面时OnInit的正常运行,并且点击添加辅助电话按钮在fi上工作首先点击。第二次点击抛出一个空引用异常(对象引用不设置为一个对象的一个实例)在此行我的OnInit方法的:
phonePnl.Controls.Add(controlToAdd);
在调试我注意到,在按钮的第一次点击,在我phoneBtn_Click方法,controlToAdd.Application,controlToAdd.Cache等也会抛出空引用异常,但它仍然生成控件并返回页面。它还将控件及其ID添加到词典中。
然后在按钮的第二次单击之前,就在它遇到导致异常的行之前,我的phonePnl变量为空。我可以推测这是导致异常的原因,但为什么我的phonePnl变量在这种情况下为空,而不是在第二次OnInit调用/第一次回发中?
我一直对这一切感慨万分,我希望有人能提供一些见解。
同样发生异常 - 有引用页LoadControl,而不是特定的控制的LoadControl有区别吗? – AWollan 2012-07-11 17:02:45