title: TagBuilder add attribute without value
body: <p>The same question from here.</p>
  
  <p><a href="https://stackoverflow.com/questions/19669731/how-to-add-attribute-without-value">How to add attribute without value</a></p>
  
  <p>This time, I want to create an input with AngularJS attribute, to use it as a directive.</p>
  
  <p>Here is what I want:</p>
  
  <pre><code>&lt;input ng-angular-abc /&gt;
  </code></pre>
  
  <p>This is what the TagBuilder generated:</p>
  
  <pre><code>&lt;input ng-angular-abc=""/&gt;
  </code></pre>
  
  <p>I have tried this, but none works:</p>
  
  <pre><code>tagBuilder.MergeAttribute("ng-angular-abc", "");
  tagBuilder.MergeAttribute("ng-angular-abc", null);
  tagBuilder.MergeAttribute("ng-angular-abc", "ng-angular-abc");
  </code></pre>