自定义ASP.net服务器控件-渲染

这是因为在任何给定时刻,控件只能属于一个父级。当您将一个集合中的控件添加到另一个集合时,它会自动从第一个集合中删除。在您的情况下:

for (int i = 0; i < Controls.Count; i++)
{
   //obtain a reference
   Control control = Controls[i];
   //The control is removed from Controls collection 
   //and added to content.Controls. All remaining controls get shifted left.
   //This means that next control will get skipped.
   content.Controls.Add(control);
}

Control[] controls = new Control[Controls.Count];
Controls.CopyTo(controls, 0); //create a snapshot of controls

for (int i = 0; i < controls.Length; i++)
    content.Controls.Add(controls[i]);

或使用反向加法:

Control[] controls = new Control[Controls.Count];
for (int i = Controls.Count - 1; i >= 0; i--) //walk backwards
    controls[i] = Controls[i];

for (int i = 0; i < controls.Length; i++)
    content.Controls.Add(controls[i]);

摆弄Controls集合,特别是在Control容器之间删除和交换控件并不总是有效的。

display:none

例如

<myCtrl:CollapsiblePanel id="myCollapsiblePanel" runat="server" Text="Panel title">
   <asp:Label id="lblTest" runat="server" Text="Test Label:"/>
   <asp:TextBox id="txbTest" runat="server"/>
</myCtrl:CollapsiblePanel>

你可能应该在CreateChildControls重载中创建并应用这个:

protected override CraeteChildControls() 
{
    Controls.Add(new LiteralControl("<"+"h1>"+Text+"<a onclick=\"expandPanel\">[+]</a></h1>"));    
    Panel panel=new Panel();
    // add controls in collapsable panel to panel here
    Controls.Add(panel);
}

<div id="ctl00_etc_myCollapsiblePanel">
   <h1>Panel title <a onclick="expandPanel">[+]</a></h1>
   <div id="childPanel" style="display:none">
      <label id="ctl_00_etc">Test Label</label>
      <input ... />
   </asp:Panel>
</div>

以及一些jQuery(或类似的)附加到 <a> :

function expandPanel() {
    $('<%=childPanel.ClientID %>').css('display','block');
}

当然,所有这些都是伪代码。