Adding a ServiceReference programmatically during async postback - asp.net

Question

Is it possible to add a new ServiceReference instance to the ScriptManager on the Page during an asynchronous postback so that subsequently I can use the referenced web service through client side script?
I'm trying to do this inside a UserControl that sits inside a Repeater, that's why adding the ScriptReference programmatically during Page_Load does not work here.
EDIT 2: This is the code I call from my UserControl which does not do what I expect (adding the ServiceReference to the ScriptManager during the async postback):
private void RegisterWebservice(Type webserviceType)
{
var scm = ScriptManager.GetCurrent(Page);
if (scm == null)
throw new InvalidOperationException("ScriptManager needed on the Page!");
scm.Services.Add(new ServiceReference("~/" + webserviceType.Name + ".asmx"));
}
My goal is for my my UserControl to be as unobtrusive to the surrounding application as possible; otherwise I would have to statically define the ServiceReference in a ScriptManagerProxy on the containing Page, which is not what I want.
EDIT:
I must have been tired when I wrote this post... because I meant to write ServiceReference not ScriptReference. Updated the text above accordingly.
Now I have:
<asp:ScriptManagerProxy runat="server" ID="scmProxy">
<Services>
<asp:ServiceReference Path="~/UsefulnessWebService.asmx" />
</Services>
</asp:ScriptManagerProxy>
but I want to register the webservice in the CodeBehind.

Answer 1

Try something like this...
if (ScriptManager.GetCurrent(this).IsInAsyncPostBack)
{
ScriptManager.RegisterClientScriptInclude(this, this.GetType(), "script1", "~/js/myjs.js");
}

Answer 2

Edit:
After checking your issue, Here is the reason why it is not working:
When you add ServiceReference to ScriptManager > Services section manually in page. It adds 1 client script include directive.
e.g:
<script src="TestService.asmx/jsdebug" type="text/javascript"></script>
or
<script src="TestService.asmx/js" type="text/javascript"></script>
which provide you to accessibility to your Frontend.Web.YourScriptMethods,
Now when you add ServiceReference in async postback - It is not adding this client script inclue. So you get client script error - method is undefined.
But i figured out a workaround for this; (do not know it is right way to do it)
if (ScriptManager.GetCurrent(this).IsInAsyncPostBack)
{
ScriptManager.RegisterClientScriptInclude(this, this.GetType(), "testservice", "TestService.asmx/js");
}
You can replace the "TestService.asmx" path according to your project/web service.
This way you can achieve what you want.
Hope this helps,
Krunal Mevada
Old Ans:
Use following:
if (ScriptManager.GetCurrent(this).IsInAsyncPostBack)
{
ScriptManager.GetCurrent(this).Services.Add(new ServiceReference("~/Service.asmx"));
}