我的页面上有一个LinkButton，点击后，我想在页面中添加一个Usercontrol。我需要能够添加/删除用户想要的控件。 Usercontrol由三个下拉列表组成。第一个下拉列表将auotpostback属性设置为true并挂起OnSelectedIndexChanged事件，该事件在被触发时将使用适当的值加载剩余的两个下拉列表。
我的问题是，无论我将代码放在主页中的哪个位置，都没有正确加载usercontrol。我知道我必须在每个回发上重新创建用户控件，并且我已经创建了一个在托管页面OnPreInit方法中执行的方法。我仍然收到以下错误： 在DataBind，Init，Load，PreRender或Unload阶段无法修改控件集合。
这是我的代码： 谢谢!!!!
bool createAgain = false;
IList<FilterOptionsCollectionView> OptionControls
{
get
{
if (SessionManager.Current["controls"] != null)
return (IList<FilterOptionsCollectionView>)SessionManager.Current["controls"];
else
SessionManager.Current["controls"] = new List<FilterOptionsCollectionView>();
return (IList<FilterOptionsCollectionView>)SessionManager.Current["controls"];
}
set
{
SessionManager.Current["controls"] = value;
}
}
protected void Page_Load(object sender, EventArgs e)
{
Master.Page.Title = Title;
LoadViewControls(Master.MainContent, Master.SideBar, Master.ToolBarContainer);
}
protected override void OnPreInit(EventArgs e)
{
base.OnPreInit(e);
System.Web.UI.MasterPage m = Master;
Control control = GetPostBackControl(this);
if ((control != null && control.ClientID ==
(lbAddAndCondtion.ClientID) || createAgain))
{
createAgain = true;
CreateUserControl(control.ID);
}
}
protected void AddAndConditionClicked(object o, EventArgs e)
{
var control = LoadControl("~/Views/FilterOptionsCollectionView.ascx");
OptionControls.Add((FilterOptionsCollectionView)control);
control.ID = "options" + OptionControls.Count.ToString();
phConditions.Controls.Add(control);
}
public event EventHandler<Insight.Presenters.PageViewArg> OnLoadData;
private Control FindControlRecursive(Control root, string id)
{
if (root.ID == id)
{
return root;
}
foreach (Control c in root.Controls)
{
Control t = FindControlRecursive(c, id);
if (t != null)
{
return t;
}
}
return null;
}
protected Control GetPostBackControl(System.Web.UI.Page page)
{
Control control = null;
string ctrlname = Page.Request.Params["__EVENTTARGET"];
if (ctrlname != null && ctrlname != String.Empty)
{
control = FindControlRecursive(page, ctrlname.Split('$')[2]);
}
else
{
string ctrlStr = String.Empty;
Control c = null;
foreach (string ctl in Page.Request.Form)
{
if (ctl.EndsWith(".x") || ctl.EndsWith(".y"))
{
ctrlStr = ctl.Substring(0, ctl.Length - 2);
c = page.FindControl(ctrlStr);
}
else
{
c = page.FindControl(ctl);
}
if (c is System.Web.UI.WebControls.CheckBox ||
c is System.Web.UI.WebControls.CheckBoxList)
{
control = c;
break;
}
}
}
return control;
}
protected void CreateUserControl(string controlID)
{
try
{
if (createAgain && phConditions != null)
{
if (OptionControls.Count > 0)
{
phConditions.Controls.Clear();
foreach (var c in OptionControls)
{
phConditions.Controls.Add(c);
}
}
}
}
catch (Exception ex)
{
throw ex;
}
}
这是usercontrol的代码：
<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="FilterOptionsCollectionView.ascx.cs" Inherits="Insight.Website.Views.FilterOptionsCollectionView" %>
namespace Insight.Website.Views
{ [ViewStateModeById] public partial class FilterOptionsCollectionView：System.Web.UI.UserControl { protected void Page_Load（object sender，EventArgs e） {
}
protected override void OnInit(EventArgs e)
{
LoadColumns();
ddlColumns.SelectedIndexChanged += new RadComboBoxSelectedIndexChangedEventHandler(ColumnsSelectedIndexChanged);
base.OnInit(e);
}
protected void ColumnsSelectedIndexChanged(object o, EventArgs e)
{
LoadCriteria();
}
public void LoadColumns()
{
ddlColumns.DataSource = User.GetItemSearchProperties();
ddlColumns.DataTextField = "SearchColumn";
ddlColumns.DataValueField = "CriteriaSearchControlType";
ddlColumns.DataBind();
LoadCriteria();
}
private void LoadCriteria()
{
var controlType = User.GetItemSearchProperties()[ddlColumns.SelectedIndex].CriteriaSearchControlType;
var ops = User.GetItemSearchProperties()[ddlColumns.SelectedIndex].ValidOperators;
ddlOperators.DataSource = ops;
ddlOperators.DataTextField = "key";
ddlOperators.DataValueField = "value";
ddlOperators.DataBind();
switch (controlType)
{
case ResourceStrings.ViewFilter_ControlTypes_DDL:
criteriaDDL.Visible = true;
criteriaText.Visible = false;
var crit = User.GetItemSearchProperties()[ddlColumns.SelectedIndex].SearchCriteria;
ddlCriteria.DataSource = crit;
ddlCriteria.DataBind();
break;
case ResourceStrings.ViewFilter_ControlTypes_Text:
criteriaDDL.Visible = false;
criteriaText.Visible = true;
break;
}
}
public event EventHandler OnColumnChanged;
public ISearchCriterion FilterOptionsValues { get; set; }
}
}
答案 0 :(得分：1)
我明白了。这是我的解决方案：
我修改了GetPostBackControl，不仅要查找插入用户控件的链接按钮，还要查找包含插入的用户控件的子控件id的控件（以捕获从我的用户控件中触发的OnSelectedIndexChanged）
protected Control GetPostBackControl(System.Web.UI.Page page)
{
Control control = null;
string ctrlname = Page.Request.Params["__EVENTTARGET"];
if (ctrlname != null && ctrlname != String.Empty)
{
//if it contains options then it's a control inside my usercontrol
if (ctrlname.Split('$')[2].Contains("options"))
{
var c = new Control();
c.ID = ctrlname;
return c;
}
else
{
control = FindControlRecursive(page, ctrlname.Split('$')[2]);
}
}
else
{
string ctrlStr = String.Empty;
Control c = null;
foreach (string ctl in Page.Request.Form)
{
if (ctl.EndsWith(".x") || ctl.EndsWith(".y"))
{
ctrlStr = ctl.Substring(0, ctl.Length - 2);
c = page.FindControl(ctrlStr);
}
else
{
c = page.FindControl(ctl);
}
if (c is System.Web.UI.WebControls.CheckBox ||
c is System.Web.UI.WebControls.CheckBoxList)
{
control = c;
break;
}
}
}
return control;
}
然后我修改OnPreInit事件以查找id为linkbutton的控件或包含“options”的id：
protected override void OnPreInit(EventArgs e)
{
base.OnPreInit(e);
System.Web.UI.MasterPage m = Master;
Control control = GetPostBackControl(this);
if (control != null)
{
if ((control.ClientID == (lbAddAndCondtion.ClientID) || createAgain) || control.ID.Contains("options"))
{
createAgain = true;
CreateUserControl(control.ID);
}
}
}
关键修复是在CreateUserControl方法中。在我的原始代码中，我试图从存储在Session中的通用列表中直接加载用户控件。我将其更改为实际创建用户控件的新实例，为该新实例分配与Session中存储的id匹配的id，然后将其添加到占位符：
protected void CreateUserControl(string controlID)
{
try
{
if (createAgain && phConditions != null)
{
if (OptionControls.Count > 0)
{
phConditions.Controls.Clear();
foreach (var c in OptionControls)
{
FilterOptionsCollectionView foc = new FilterOptionsCollectionView();
foc = Page.LoadControl("~/Views/FilterOptionsCollectionView.ascx") as FilterOptionsCollectionView;
foc.ID = c.ID;
phConditions.Controls.Add(foc);
}
}
}
}
catch (Exception ex)
{
throw ex;
}
}
我在用户控件中唯一改变的是移动加载我的下拉列表的方法，并将OnSelectedIndexChanged事件连接到OnInit事件。现在我可以动态加载我想要的用户控件的多个实例，并且用户控件内的所有事件都正确地触发，并且状态在回发中保持不变!!
希望这有助于其他人!!