using System;

using System.Linq;

using System.Collections.Generic;                   

using System.Collections;                   

using System.Xml;                   

using System.Xml.Linq;

using System.Data;

using System.Data.DataSetExtensions;

using System.Data.Linq;

using System.Runtime;                                       

using System.Runtime.Remoting;

using System.Globalization;

using System.Runtime.CompilerServices;

using System.Xml.XPath;

​

using System.Reflection;

​

public class Program

{

    public static void Main()

    {

        string input = @"<FareSearchResponse>

    <AirlineList>

        <AQR>...</AQR>

        <ABA>...</ABA>

        <AAI>...</AAI>

        <A9W>...</A9W>

        <AVS>...</AVS>

        <AAF>...</AAF>

        <AEY>...</AEY>

        <ALH>...</ALH>

        <AQF>...</AQF>

    </AirlineList>

</FareSearchResponse>";

        // Using XDocument

        var doc = XDocument.Parse(input);

        foreach (var element in doc.Descendants("AirlineList").Elements())

        {

            element.Name ="Airline";

        }

        doc.Dump(); 

        // Using XElement

        var doc1 = XElement.Parse(input);

        foreach(var element in doc1.Descendants("AirlineList").Elements()) 

        {

            element.Name ="Airline";

        }

        doc1.Dump();

        //doc.Save()

    }

}

​

​

​

​

​