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copied!<p>You can write the filter in the <code>Where</code> clause the following way:</p> <pre><code>.Where(t => t.Content is Image && !(t.Content as Image).Private) </code></pre> <p>However, the bigger problem is the <code>Include</code> part. The <code>Author</code> property only exists for the derived type <code>Image</code> but <code>Include</code> will try to load the base type <code>Content</code> (which doesn't have an <code>Author</code> property) because that's the type of the navigation property <code>Content</code> in <code>Tag</code>. You just can't use <code>Include</code> here.</p> <p>You can try to rewrite the query as a projection:</p> <pre><code>var tags = context.Tags .Where(t => t.Content is Image && !(t.Content as Image).Private) .Select(t => new { Tag = t, Image = t.Content as Image, // possibly this line is not needed Author = (t.Content as Image).Author, Person = t.Person }) .AsEnumerable() .Select(x => x.Tag) .ToList(); </code></pre> <p>As long as you don't disable change tracking (with <code>AsNoTracking</code> for example) EF should put the object graph together automatically so that the loaded tags have a populated <code>Content</code>, <code>Content.Author</code> and <code>Person</code> property (<em>as if</em> you had loaded the navigation properties with <code>Include</code>).</p> <p>BTW: The feature to include navigation properties of a derived type is requested <a href="http://data.uservoice.com/forums/72025-entity-framework-feature-suggestions/suggestions/1249289-include-property-of-derived-classes" rel="noreferrer">here on UserVoice</a>. It's not exactly the same as your situation, but in the comment section is a request even for your scenario.</p>

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