using System;

using System.Linq;

using System.Xml.Linq;

​

public static class Program

{

    public static void Main(string[] args)

    {

        var xml = @"<ScheduledCustomerJourneys>

  <ScheduledCustomerJourney ScheduledCustomerJourneyId=""534454"" />

  <ScheduledCustomerJourney ScheduledCustomerJourneyId=""534455"" />

  <ScheduledCustomerJourney ScheduledCustomerJourneyId=""534455"" />

  <ScheduledCustomerJourney ScheduledCustomerJourneyId=""538020"" />

  <ScheduledCustomerJourney ScheduledCustomerJourneyId=""538020"" />

  <ScheduledCustomerJourney ScheduledCustomerJourneyId=""538020"" />

  <ScheduledCustomerJourney ScheduledCustomerJourneyId=""538020"" />

  <ScheduledCustomerJourney ScheduledCustomerJourneyId=""531228"" />

  <ScheduledCustomerJourney ScheduledCustomerJourneyId=""534457"" />

  <ScheduledCustomerJourney ScheduledCustomerJourneyId=""526977"" />

  <ScheduledCustomerJourney ScheduledCustomerJourneyId=""526978"" />

  <ScheduledCustomerJourney ScheduledCustomerJourneyId=""538023"" />

  <ScheduledCustomerJourney ScheduledCustomerJourneyId=""534459"" />

  <ScheduledCustomerJourney ScheduledCustomerJourneyId=""534459"" />

</ScheduledCustomerJourneys>";

​

        var doc = XDocument.Parse(xml);

​

        doc.Descendants("ScheduledCustomerJourney")

            .GroupBy(x => x.Attribute("ScheduledCustomerJourneyId").Value)

            .SelectMany(x => x.Key == string.Empty ? x : x.Skip(1))

            .Remove();

​

​

        Console.WriteLine(doc.ToString());

    }

}