In Order to make my logo dynamic(coming from CMS), I created a CT which can add any image to a header page having PT "Include Page".
But Now I want that CT to be available for one page i.e. header page only. As that CT can be added to any page and it is rendering a logo of that specific page which shouldn't be the case.
Any suggestions?
Another option would be to use Event System on Page Save and interrupt the saving if the Page Template <-> Component Template combination is not allowed. You can throw an exception with a meaningful message informing the Editors that what they're trying to achieve is not permitted.
The advantage of this approach is that you handle your specific case even before it's created VS throwing and exception from Templating or not rendering it at all (effectively masking the Component Presentation). In other words, you have a clean slate as far as the PT/CT combinations goes, effectively having a clearer overview of the current state of the system.
Naturally, this also has drawbacks, for example it will get executed each time a Page is saved slowing the system a bit, but the main concern is what about the already existing Pages which have the forbidden Component Template. For those, you could use Core Service to do a quick search and remove the Component Presentation from them.
There is no "out-of-the-box" to do this restriction - it may be coming with Region support in Tridion Sites 9, as I understand you can add restrictions like this to a region.
For now, the only way to do this is to enforce it in your Page Template - i.e., either throw an exception when you find this CT in a PT that shouldn't be used, or not render it at all - though this is not ideal, as you would have to change all Page Templates.
Edit - You could also put this logic in the CT itself, using the engine's render context (see here for more info) property to find if you're rendering in the correct page type.
A possible workaround would be to put the new Component Template into a different folder than your other 'editorial' Component Templates and then control the security permissions on that folder.
This would mean that only Tridion Administrators (and other Users/Groups that you choose) will be able to see the new Component Template as an option when adding Component Presentations to a Page.
You could do something like this in your page template.
engine.PublishingContext.RenderContext.ContextVariables.Add(
"allowDynamicLogo", true);
In your component template, you could read the context variables to see if this one is present, and if it's not, throw an exception.
