title: An exception of type 'System.ArgumentException' occurred in EntityFramework.dll but was not handled in user code
body: <p>I've faced a problem that is:</p>
  <blockquote>
  <p>An exception of type 'System.ArgumentException' occurred in EntityFramework.dll but was not handled in user code</p>
  <p>Additional information: The Include path expression must refer to a navigation property defined on the type. Use dotted paths for reference navigation properties and the Select operator for collection navigation properties.</p>
  </blockquote>
  <p>How can I solve it?</p>
  <p>This problem happen in <code>FindAll</code> method</p>
  <pre><code>articleViewModel.AttachmentFiles = AttachmentFileBLL.Instance.FindAll(c =&gt; c.ArticleId == articleViewModel.Id).ToList();
  </code></pre>
  <p>FindAll method:</p>
  <pre><code>public virtual IQueryable&lt;TModel&gt; FindAll(params Expression&lt;Func&lt;TModel, object&gt;&gt;[] includeProperties)
      {
          IQueryable&lt;TModel&gt; items = RepositoryContainer&lt;TRepository&gt;().FindAll();
  
          if (includeProperties != null)
          {
              foreach (var includeProperty in includeProperties)
              {
                  items = items.Include(includeProperty); // Problem occurred here! 
              }
          }
          return items;
      }
  </code></pre>
  <p><img src="https://i.stack.imgur.com/YDnqg.jpg" alt="Error location" /></p>
  <pre><code>public virtual int? ArticleId { get; set; }
  
  public virtual int Id { get; set; }
  </code></pre>