title: Page Flickering on Dropdown change
body: <p>I'm using a drop down list to select the customer. The page flicker twice on selecting the customer and I don't know how to rectify it. Can someone please help me solve the problem?</p>
  
  <p><strong>My Drop Down SelectedIndexChange Code</strong></p>
  
  <pre><code>protected void ReceiverDropDown_SelectedIndexChanged(object sender, EventArgs e)
  {
      if (ReceiverDropDown.SelectedValue != null &amp;&amp; ReceiverDropDown.SelectedValue != "0")
      {            
          string benId = ReceiverDropDown.SelectedValue;
          Page.ClientScript.RegisterStartupScript(this.GetType(), "alert", "AddDetails('" + benId + "');", true);
      }
  }
  </code></pre>
  
  <p><strong>Code using Update Panel</strong></p>
  
  <pre class="lang-html prettyprint-override"><code>&lt;td&gt;
      &lt;asp:UpdatePanel runat="server" ID="updTerms" UpdateMode="Conditional"&gt;
          &lt;ContentTemplate&gt;
              &lt;asp:DropDownList Width="180px" CssClass="select_quo_one" ID="ReceiverDropDown" 
                  runat="server" AutoPostBack="true"
                  OnSelectedIndexChanged="ReceiverDropDown_SelectedIndexChanged"&gt;
              &lt;/asp:DropDownList&gt;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;
          &lt;/ContentTemplate&gt;
      &lt;/asp:UpdatePanel&gt;
      &lt;Triggers&gt;
          &lt;asp:AsyncPostBackTrigger ControlID="ReceiverDropDown" /&gt;
      &lt;/Triggers&gt;
  &lt;/td&gt;
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/8Bz2X.png" alt="enter image description here"></p>