Create sitemap.xml in ASP.NET Core

The sitemap.xml file must be encoded with UTF-8. Example of sitemap:

<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
   <url>
      <loc>http://www.example.com/</loc>
      <lastmod>2005-01-01</lastmod>
      <changefreq>monthly</changefreq>
      <priority>0.8</priority>
   </url>
   <!-- ... -->
</urlset>

As you can see, each URL in a sitemap contains four pieces of metadata:

• urlset - Sitemap start and ending tag. Sitemap document start with <urlset> and ends with </urlset>
• URL - parent tag for each URL entry
• loc - URL of our site.
• lastmod (Optional) - A last modified timestamp. This tells search engines whether or not they should re-index the page to reflect any changes that have been made.
• changefreq (Optional) - A change frequency indicator (This can take the values: always, hourly, daily, weekly, monthly, yearly, never). This gives search engines an indication of how often they should come back and re-index the page.
• priority (Optional) - A number from zero to one indicating the page's importance compared to other pages on the site.

The last three values only give search engines an indication of when they can or should index or even re-index a page. It is not a guarantee that it will happen, although it makes it more likely.

A sitemap is a standalone page. On the razor page model, the ApplicationDbcontext is injected to work with the database.

Below code will generate XML string and return as ContentResult having ContentType = "application/xml". 

Our page model code looks like as written below:

namespace Sample.Pages
{
  public class SitemapModel : PageModel
  {
    public readonly ApplicationDbContext dbContext;

    public SitemapModel(ApplicationDbContext dbContext)
    {
      this.dbContext = dbContext;
    }

    public IActionResult OnGet()
    {
      var pages = dbContext.Pages.ToList();
      StringBuilder sb = new StringBuilder();
      sb.Append("<?xml version='1.0' encoding='UTF-8' ?><urlset xmlns = 'http://www.sitemaps.org/schemas/sitemap/0.9'>");

      foreach (var page in pages)
      {
        string mDate = page.ModifiedDate.ToString("yyyy-MM-ddTHH:mm:sszzz");
        var url = $"https://www.snippset.com/{page.Title}";
        sb.Append("<url><loc>" + url + "</loc><lastmod>" + mDate + "</lastmod><changefreq>{page.Frequency}</changefreq><priority>{page.Priority}</priority></url>");
      }

      sb.Append("</urlset>");

      return new ContentResult
      {
        ContentType = "application/xml",
        Content = sb.ToString(),
        StatusCode = 200
      };
    }
  }
}

ASP.NET Core provides the option to set a friendly URL. So instead of just sitemap, it can be set to sitemap.xml.

By using AddPageRoute the route to a page can be configured with a friendly URL.

options.Conventions.AddPageRoute("/Sitemap", "Sitemap.xml");

Further information for sitemap.xml

• sitemaps.org - Home
• Asp.net Core: Create Sitemap.XML dynamically with database [MySql] - Codepedia
• Create and Configure sitemap.xml in ASP.NET Core (c-sharpcorner.com)
• Dynamically Generating Sitemap.xml for ASP.NET MVC - Muhammad Rehan Saeed
• Serving sitemap.xml and robots.txt with ASP.Net core MVC - DEV Community