title: The property 'a' is not a navigation property of entity type 'b'. Why not?
body: <p>I'm trying to load a list of product identifier <code>Label</code>s (i.e. names of product identifiers, such as "EAN", "Product number", etc.) from <code>ProductIdentifiers</code> with this query:</p>
  
  <pre><code>ICollection&lt;ProductIdentifierInType&gt; typeIds =
              _context.ProductIdentifiersInTypes
              .Include(t =&gt; t.Identifier.Label)
              .OrderBy(o =&gt; o.SortOrder).ToList();
  </code></pre>
  
  <p>VS gives me intellisense for <code>t.Identifier.Label</code>. The solution compiles fine. This is the runtime error I get:</p>
  
  <blockquote>
    <p>InvalidOperationException: The property 'Label' is not a navigation property of entity type 'ProductIdentifier'. The 'Include(string)' method can only be used with a '.' separated list of navigation property names.</p>
  </blockquote>
  
  <p>Here are the relevant model classes:</p>
  
  <pre><code>public class ProductIdentifierInType
  {
      public int Id { get; set; }
      public int ProductTypeId { get; set; }
      public int SortOrder { get; set; }
  
      public ProductIdentifier Identifier { get; set; }
      public ProductType Type { get; set; }
  }
  
  public class ProductIdentifier
  {
      public int Id { get; set; }
      public string Label { get; set; }
      public int SortOrder { get; set; }
  
      public ICollection&lt;ProductIdentifierInType&gt; TypeIdentifiers { get; set; }
  }
  </code></pre>
  
  <p>My DbContext:</p>
  
  <pre><code>public class MyStoreContext : DbContext // IdentityDbContext
  {
      public MyStoreContext(DbContextOptions options) : base(options) { }
  
      // some unrelated tables ...
  
      public DbSet&lt;ProductIdentifierInType&gt; ProductIdentifiersInTypes { get; set; }
      public DbSet&lt;ProductIdentifier&gt; ProductIdentifiers { get; set; }
  
      // some more, unrelated tables ...
  }
  </code></pre>
  
  <p>I have tried inheriting from <code>IdentityDbContext</code> like the solution in <a href="https://stackoverflow.com/questions/46838328/the-property-x-is-not-a-navigation-property-of-entity-type-y">this question</a>, but that didn't make any difference.</p>
  
  <p>What is wrong?</p>