The Controls collection cannot be modified because the control contains code blocks (i.e. <% ... %>)
I am trying to add a panel as a child control of another panel in the codebehind of a master page, it's a simple as:
Panel1.Controls.Add(Panel2)
However when I try to do that, I get this error:
The Controls collection cannot be modified because the control contains code blocks (i.e. <% ... %>).
There are a number of questions that talk about having <%= %> elements in the head section, which I do not have. I have been so far as to remove all <% %> elem开发者_JS百科ents from this page, to no avail, the error still occurs. Can anyone suggest a way to get this to work?
* Example for Answer B *
=== code with error ===
<script type="text/javascript">
jQuery(document).ready(
function() {
alert('Hello!');
jQuery("#<%=TxtSampleId.ClientID %>").focus();
}
);
</script>
=== code without error ===
<asp:PlaceHolder id="dontCare" runat="server">
<script type="text/javascript">
jQuery(document).ready(
function() {
alert('Hello!');
jQuery("#<%=TxtSampleId.ClientID %>").focus();
}
);
</script>
</asp:PlaceHolder>
The "The Controls collection cannot be modified because the control contains code blocks (i.e. <% ... %>)." error can be very annoying to say the least. It's a bug that Microsoft refuses to fix because there are workarounds. It happens when you try to dynamically load controls from the code behind, but your page source conflicts. Could be a few things going on...
Note: Stack Overflow doesn't handle syntax of code examples well, so I'll reference each answer with a letter, and in a later post, I'll attempt to type out an example. But I don't want to clutter this post because I want to get my points across.
A.) you have a <% Response.Write("something") %> in your page source. Or a <% CodeBehindMethod() %>. Remove it and be creative to populate it a different way!! One way is to place an ASP.NET Panel control (like a Panel ==> turns into a div tag when it renders to HTML) onto your page and dynamically populate the inner HTML attribute of that control. There are other ways of dealing with this.
B.) you are trying to use jQuery inside of an inline script block within your control, you will also get this. Surround the inline javascript code block with an ASP.NET PlaceHolder tag. It's that simple. If you don't, some jQuery functionality will work, but not all of it!
C.) If you are using Script Manager without a Masterpage, I'd suggest you start using a Masterpage to avoid issues later. Then use an ASP.NET ContentPlaceHolder for your head and your body tags to make customizing pages easier. When you reference your javascript files within your masterpage, and you're using Script Manager, make sure to put a Scripts tag inside your ScriptManager tag. Then inside the Scripts tag, place a ScriptReference tag with a Path of the full path of your Javascript files in there. Make sure to put a tilda and forward slash "~/" in the beginning of your path from the root of your web app. Many will put their ScriptManager tag in their control. Don't do this. Put it in your masterpage! It makes life easier.
D.) If A, B or C didn't answer your question, then I'd suggest stripping away every piece of your page and all controls in it, and add each one at a time. If you have a huge hierarchy of page and control inheritance (if your application doesn't have a Masterpage), good luck! You'll eventually figure out what caused it.
* Example for Answer C *
=== code without error ===
Masterpage code:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><meta http-equiv="X-UA-Compatible" content="IE=7" />
<html xmlns="http://www.w3.org/1999/xhtml">
<title>Stack Overflow Example</title>
<link rel="stylesheet" type="text/css" href="/style/jquery-ui-1.8.10.custom.css">
<asp:ContentPlaceHolder id="head" runat="server"> <asp:ContentPlaceHolder>
</head>
<body>
<form id="Form1" method="post" runat="server">
<asp:ScriptManager ID="anything" runat="server">
<Scripts>
<asp:ScriptReference Path="~/scripts/md5.js" />
<asp:ScriptReference Path="~/scripts/jquery-1.4.4.min.js" />
<asp:ScriptReference Path="~/scripts/jquery-ui-1.8.10.custom.min.js" />
<asp:ScriptReference Path="~/custom_crap.js" />
</Scripts>
</asp:ScriptManager>
<asp:ContentPlaceHolder id="body" runat="server">
</asp:ContentPlaceHolder>
</form>
</body> </html>
====================================================
Page source:
<asp:Content runat="server" ID="headcontent" ContentPlaceHolderID="head"> .. place your page specific header files here (js, css, etc..) </asp:Content>
<asp:Content runat="server" ID="bodycontent" ContentPlaceHolderID="body"> .. place your page specific body HTML or ASP.NET code here </asp:Content>
加载中,请稍侯......
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