I am trying to create dynamic meta tags in C# but it gives the following error:
The Controls collection cannot be modified because the control contains code blocks (i.e. <% ... %>)
This is the code I added:
HtmlMeta meta = new HtmlMeta();
meta.Name = "keywords";
meta.Content = "book,paper";
Page.Header.Controls.Add(meta);
Thank you very much.
This question is related to
c#
Just in case if you are using Telerik components and you have a reference in your javascript with <%= .... %> then wrap your script tag with a RadScriptBlock.
<telerik:RadScriptBlock ID="radSript1" runat="server">
<script type="text/javascript">
//Your javascript
</script>
</telerik>
Regards Örvar
Inside ContentPlaceholder, put the placeholder control.For Example like this,
<asp:Content ID="header" ContentPlaceHolderID="head" runat="server">
<asp:PlaceHolder ID="metatags" runat="server">
</asp:PlaceHolder>
</asp:Content>
Code Behind:
HtmlMeta hm1 = new HtmlMeta();
hm1.Name = "Description";
hm1.Content = "Content here";
metatags.Controls.Add(hm1);
Check out the solutions at "The Controls collection cannot be modified because the control contains code blocks"
The accepted solution on the other question worked for me -- change instances of <%= to <%#, which converts the code block from Response.Write to an evaluation block, which isn't restricted by the same limitations.
In this case though, like the accepted solution here suggests, you should add the controls to something other than a masterpage ContentPlaceHolder element, namely the asp:Placeholder control suggested.
For those using Telerik as mentioned by Ovar, make sure you wrap your javascript in
<telerik:RadScriptBlock ID="radSript1" runat="server">
<script type="text/javascript">
//Your javascript
</script>
</telerik>
Since Telerik doesn't recognize <%# %> when looking for an element and <%= %> will give you an error if your javascript code isn't wrapped.
Not really solve your question but it's an important alternative.
If you want to add custom html to the beginning of the page (inside <body> element), you may use Page.ClientScript.RegisterClientScriptBlock().
Although the method is called "script", but you can add arbitary string, including html.
I have had the same issue that I solved this way:
Instead of adding the meta to the current page header that caused the same error as you had:
Page.Header.Controls.Add(meta);
I used this instead:
Master.FindControl("YourHeadContentPlaceHolder").Controls.Add(meta);
and it works like a charm.
Source: Stackoverflow.com