How to validate duplicate values for an xml tag in asp.net?

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ASP.NET

XML

C#3.5

How to validate duplicate values for an xml tag in asp.net?
There are duplicate values for the Payroll Account Id. Has to validate if the same tag contains duplicates .I want to check without using LINQ
My Xml Tag is as below:

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:cus="http://wps.fgb.com/CustomerOnboard/" xmlns:cry="http://util.fgb.com/Crypt">
  <soapenv:Header/>
  <soapenv:Body>
    <cus:getOnboardingDetails>

            <molId></molId>
            <payrollAccountId>19498235345</payrollAccountId>
             <payrollAccountId>19498235345</payrollAccountId>

    </cus:getOnboardingDetails>
  </soapenv:Body>
</soapenv:Envelope>