title: aspx page not load in iframe click on button
body: <pre><code>&lt;asp:Button runat="server" ID="hiddenPopupPatientRegistration" Style="display: none" /&gt;
      &lt;asp:ModalPopupExtender ID="popupPatientRegistration" runat="server" PopupControlID="panelPatientRegistration"
          TargetControlID="hiddenPopupPatientRegistration" BackgroundCssClass="cssmodalbackground"
          BehaviorID="modalBehaviour" CancelControlID="btnClose"&gt;
      &lt;/asp:ModalPopupExtender&gt;
      &lt;div id="panelPatientRegistration" class="cssmodalpopup" style="display: none"&gt;
          &lt;iframe id="iframePatientRegistration"  class="csstable" runat="server" width="600px"
              height="485px" scrolling="auto"&gt;&lt;/iframe&gt;
          &lt;table&gt;
              &lt;tr&gt;
                  &lt;td align="right"&gt;
                      &lt;asp:Button ID="btnClose" runat="server" CssClass="cssbutton" Text="Close" /&gt;
                  &lt;/td&gt;
              &lt;/tr&gt;
          &lt;/table&gt;
      &lt;/div&gt;
  
      protected void btn_Click(object sender, EventArgs e)
      {
            iframePatientRegistration.Attributes["src"] = "Patient_Registration.aspx?flowType=" + flowType + "&amp;fromTime=" + hidFromTime.Value + "&amp;toTime=" + hidToTime.Value + "&amp;acqModalityID=" + hidAcqModalityID.Value + "&amp;schLocationID=" + ddlScheduledProcedureStepLocation.SelectedValue;
              popupPatientRegistration.Show();
      }
  </code></pre>
  
  <p>I have to show aspx page in modal popup extender control.
   And pass values through query string
   BUT ASPX page not loads in Iframe.code behind.</p>
  
  <p>when i see html source then getting these two lines</p>
  
  <pre><code>&lt;HTML&gt;
  &lt;/HTML&gt;
  </code></pre>