title: Cannot convert lambda expression to type 'string' because it is not a delegate type
body: <p>I'm building a page that shows a LINQ query result as a table.</p>
  
  <ol>
  <li>Setup the base query in the 'SetupArticleQuery()' method which saves the query to 'this.articles'.</li>
  <li>Run another method, 'UpdateFilter()' to do some filtering on the results that are saved in 'this.articles'.</li>
  </ol>
  
  <p>I get the error</p>
  
  <blockquote>
    <p>Cannot convert lambda expression to type 'string' because it is not a delegate type</p>
  </blockquote>
  
  <p>at the line with the code</p>
  
  <pre><code>this.articles = from art in this.articles
                  where art.category_id == this.categoryId
                  select art;
  </code></pre>
  
  <p>Any ideas how to fix the code below?</p>
  
  <pre><code>namespace WebApplication3 {
      public partial class _Default : System.Web.UI.Page {
          private IQueryable articles;
  
          protected void Page_Load(object sender, EventArgs e) {
              this.SetupArticleQuery();
              this.UpdateFilter();
          }
  
          private void SetupArticleQuery() {
              this.articles = from a in KB.Articles
                              join t in KB.Teams on a.primary_team_id equals t.id
                              join cat in KB.Categories on a.category_id equals cat.id
                              join scat in KB.SubCategories on a.subcategory_id equals scat.id
                              join top in KB.Topics on a.topic_id equals top.id
                              select new {
                                  a.id,
                                  a.title,
                                  a.view_count,
                                  a.created_at,
                                  a.created_by,
                                  a.primary_team_id,
                                  primary_team_name = t.name,
                                  category_id = cat.id,
                                  category_name = cat.name,
                                  subcategory_id = scat.id,
                                  subcategory_name = scat.name,
                                  topic_id = top.id,
                                  topic_name = top.name
                              };
          }
  
          private void UpdateFilter() {
              if (this.categoryId &gt; 0) {
                  this.articles = from art in this.articles
                                  where art.category_id == this.categoryId
                                  select art;
  
              }
          }
  }
  </code></pre>