How to check if client script is already registered during a partial postback

Question

Below is the code I've currently implemented.

if (!Page.ClientScript.IsStartupScriptRegistered(Page.GetType(), scriptKey))
{
  ScriptManager scriptManager = ScriptManager.GetCurrent(page);
  if (scriptManager != null && scriptManager.IsInAsyncPostBack)
  {
    //if a MS AJAX request, use the Scriptmanager class
    ScriptManager.RegisterStartupScript(Page, Page.GetType(), scriptKey, script, true);
  }
  else
  {
    //if a standard postback, use the standard ClientScript method
    Page.ClientScript.RegisterStartupScript(Page.GetType(), scriptKey, script, true);
  }
}

I'm doing as suggested in this answer so that I can register startup script on both times i.e. when there is partial postback and a full postback.

The problem is Page.ClientScript.IsStartupScriptRegistered(Page.GetType(), scriptKey) always (even when the script is registered before) returns false when it is partial postback. And I couldn't find ScriptManager.IsStartupScriptRegistered (static) method. As a result of this, additional script is emitted on all partial/async postbacks.

Please note that I'm using script manager of AjaxControlToolkit version 4.1 i.e. ToolkitScriptManager in my masterpage. But I don't thing it has something to do with this.

UPDATE

  <asp:UpdatePanel ID="ContactDetailsUpdatePanel" UpdateMode="Conditional" runat="server">
    <Triggers>
      <asp:AsyncPostBackTrigger ControlID="UpdateContactDetailsButton" EventName="Click" />
    </Triggers>
    <ContentTemplate>
      <div id="ContactDetailsContent" class="contact_details_content">
        <div class="customer_contactdetails_left_pane">
          <div class="customer_name_field">
            <asp:Label ID="CustomerNameLabel" runat="server" Text="Customer" />
            <asp:TextBox ID="CustomerNameValue" runat="server" />
          </div>
          <div class="customer_address_field">
            <asp:Label ID="CustomerAddressLabel" runat="server" Text="Address" />
            <asp:TextBox ID="CustomerAddressValue" runat="server" />
            <asp:TextBox ID="CustomerAddressValue1" runat="server" />
            <asp:TextBox ID="CustomerAddressValue2" runat="server" />
            <asp:TextBox ID="CustomerAddressValue3" runat="server" />
          </div>
          <div class="customer_postcode_field">
            <asp:Label ID="CustomerPostcodeLabel" runat="server" Text="Postcode" />
            <asp:TextBox ID="CustomerPostcodeValue" runat="server" />
          </div>
        </div>
        <div class="customer_contactdetails_right_pane">
          <div>
            <asp:Label ID="CustomerContactLabel" runat="server" Text="Contact" />
            <asp:TextBox ID="CustomerContactValue" runat="server" />
          </div>
          <div>
            <asp:Label ID="CustomerTelephoneLabel" runat="server" Text="Telephone" />
            <asp:TextBox ID="CustomerTelephoneValue" runat="server" />
          </div>
          <div>
            <asp:Label ID="CustomerMobileLabel" runat="server" Text="Mobile" />
            <asp:TextBox ID="CustomerMobileValue" runat="server" />
          </div>
          <div>
            <asp:Label ID="CustomerFaxLabel" runat="server" Text="Fax" />
            <asp:TextBox ID="CustomerFaxValue" runat="server" />
          </div>
          <div>
            <asp:Label ID="CustomerEmailLabel" runat="server" Text="Email" />
            <asp:TextBox ID="CustomerEmailValue" runat="server" />
          </div>
          <div>
            <asp:Label ID="CustomerWebLabel" runat="server" Text="Web" />
            <asp:TextBox ID="CustomerWebValue" runat="server" />
          </div>
        </div>
      </div>
      <div class="update_button_field">
        <asp:Button ID="UpdateContactDetailsButton" runat="server" Text="Update" 
          onclick="UpdateContactDetailsButton_Click" />
      </div>          
    </ContentTemplate>    
  </asp:UpdatePanel>

Thanks in advance.

NOTE: To be able to understand the progress on this problem, please see the comments on this answer before replying.

UPDATE
I have implemented a temporary solution to this problem by putting a check in javascript that if the script is already executing then do not execute twice. Javascript is still being spitted multiple times on every partial postback. Couldn't prevent it.

As the views to this post are increasing, I can see that there are other people who might also want answer to this problem.

Answer 1

If you are using this;

Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "noPasswordMatch", script, true);

Then to check if it has been registered you must use this:

if (Page.ClientScript.IsClientScriptBlockRegistered(this.GetType(), "noPasswordMatch"))

if (Page.ClientScript.IsClientScriptBlockRegistered("noPasswordMatch")) doesn't work!