title: How to set source of video tag in code behind?
body: <p>I use this code in ASPX file:</p>
  
  <pre><code> &lt;video width="320" height="240" autoplay="autoplay"&gt;
      &lt;source id="videoSrc" runat="server"  type="video/mp4"/&gt;
      Your browser does not support the video tag.
   &lt;/video&gt;
  </code></pre>
  
  <p>but when I use this code in code behind:</p>
  
  <pre><code>protected void Page_Load(object sender, EventArgs e)
  {
      videoSrc.Src= "UploadMovies/"+Request.QueryString["id"]+"/high.mp4";
  }
  </code></pre>
  
  <p>and call my page as <em><code>myPage.aspx?id=1</code></em> I get this error on <code>&lt;source&gt;</code>:</p>
  
  <blockquote>
    <p>The base class includes the field 'videoSrc', but its type (System.Web.UI.HtmlControls.HtmlSource) is not compatible with the type of control (System.Web.UI.HtmlControls.HtmlGenericControl).</p>
  </blockquote>