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CSharp · Console

/Program.cs

using System;
using System.Xml.Linq;

public class Program
{
	public static void Main()
	{
		var doc = new XDocument(
			new XElement("request",
				new XElement("transaction", 
					new XAttribute("transactionId", "123"),
					new XElement("transactionDetail", new XAttribute("transactionId", "123"))
					)
				)
			);
		
		Console.WriteLine(doc);
							 
	}
}