The Controls collection cannot be modified because the control contains code blocks (i.e. <% … %>)

Question

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 conta

Answer 1

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.