title: Get selected extensions or no extension returned from bundle search FHIR using c#
body: <p>I'm totally new to this so pardon my use of terminologies.</p>
  <p>I want to know how can i use <code>SearchParams</code> so i can select not all but a few selected extensions or dont include any extention in the bundle when i search for a bundle.</p>
  <p>Suppose my bundle has 3 extensions</p>
  <pre class="lang-json prettyprint-override"><code>extension: [{
          &quot;extension&quot;: [
            {
              &quot;url&quot;: &quot;ABC&quot;,
              &quot;valueId&quot;: &quot;00000000-0000-0000-000e-00000000000p&quot;
            },
            {
              &quot;url&quot;: &quot;DEF&quot;,
              &quot;valueId&quot;: &quot;00000005-0000-0000-0000-000000000000&quot;
            },
            {
              &quot;url&quot;: &quot;HIJ&quot;,
              &quot;valueId&quot;: &quot;00000005-000K-0000-0000-000000000000&quot;
            }, {..next extention object}]
  </code></pre>
  <p>Now what if i only want ABC and DEF in my extension array how can i do that in C# using <code>Hl7.Fhir</code></p>