Sitefinity: How to add link in the header from backend?

Question

Let me explain more about the page orientation.

Used
|_ Forklift
|_ Boomlift
|_ Specs

Every time you wanna see the list of forklift you go to "/Used/Forklift". You can see the all the forklifts. There may be several same model with same capacity used forklifts. So when users click on a specific item/forklift, they get redirected to the common page "Used/Specs/"; in addition we send 2 additional parameter (bold ones in the url). So the url looks like this;

http://localhost:60876/used/specs/used-forklifts/2015-hyundai-160d-7a-ls10151

Now, we have a widget on the "Specs" page; using these two parameters widget controller calls an API to get forklift details; on Sitefinity side we don't have any model (Nothing in the module), all done by the scripts to populate forklift details. That's not a problem, all working fine.

I set the page not to show Canonical url it doesn't show that; fine as well. But how can I add a custom link in the head from the server side? Something like the following;

                HtmlLink canonicalLink = new HtmlLink();
                canonicalLink.Attributes.Add("rel", "canonical");
                canonicalLink.Attributes.Add("href", "test");

And I have something like this;

I have tried so many things nothing works. Thank you for your help. My Sitefinity version is 10.2.6631.

Answer 1

You can check this blog post that shows how to remove (if exists) and add a canonical link in Sitefinity. You can modify it a bit to fit to your needs.

Answer 2

Thank you @Veselin Vasilev for pointing me to the solution. According to his blog here is the total changes I've made.

In Global.asax

 protected void Application_Start(object sender, EventArgs e)
    {            
        SystemManager.ApplicationStart += SystemManager_ApplicationStart;
    }

Then copied SystemManager_ApplicationStart from the blog;

private void SystemManager_ApplicationStart(object sender, EventArgs e)
    {
        EventHub.Subscribe<IPagePreRenderCompleteEvent>(evt => PagePreRenderCompleteEvent(evt));
    }

Lastly modify a bit PagePreRenderCompleteEvent to change the canonical URL;

private void PagePreRenderCompleteEvent(IPagePreRenderCompleteEvent evt)
    {
        if (!SystemManager.IsDesignMode)
        {
            var SpecsUrl = "/used/specs";

            if (evt.PageSiteNode.Url.Contains(SpecsUrl))
            {
                try
                {                        
                    var Page = evt.Page;                        

                    var Canonical = (from ctrls in Page.Header.Controls.OfType<HtmlLink>()
                                     where ctrls.Attributes["rel"].Equals("canonical", StringComparison.CurrentCultureIgnoreCase)
                                     select ctrls).FirstOrDefault();

                    if (Canonical != null)
                    {
                        Page.Header.Controls.Remove(Canonical);
                    }

                    Canonical = new HtmlLink();
                    Canonical.Attributes.Add("rel", "canonical");

                    var Href = evt.PageSiteNode.Url.Replace(SpecsUrl, SystemManager.CurrentHttpContext.Request.Url.PathAndQuery);

                    // resolve the url as absolute
                    Href = RouteHelper.ResolveUrl(Href, UrlResolveOptions.Absolute);
                    Canonical.Href = Href;

                    Page.Header.Controls.Add(Canonical);
                }
                catch (Exception e)
                {
                    Log.Write(e);                        
                }
            }
        }
    }