aspnet web api chat.cs

using System.Text.Json.Serialization;
using System.Xml;
using Newtonsoft.Json;

namespace chatik;
class Message
{
    public string Text = "";
    public string Nickname = "";
}
class Program
{
    public static void Main(string[] args)
    {
        var builder = WebApplication.CreateBuilder(args);
        var app = builder.Build();
        
        app.Map("/get", applicationBuilder =>
        {
            applicationBuilder.Run(async (context) =>
            {
                await context.Response.WriteAsJsonAsync(JsonConvert.SerializeObject(ParseXML()));
            });
        });
        app.Map("/send", applicationBuilder =>
        {
            applicationBuilder.Run(async (context) =>
            {
                var form = context.Request.Form;
                AddData(form["nickname"], form["text"]);
                await context.Response.WriteAsync("sent!");
            });
        });
        
        app.Run(async context => await context.Response.SendFileAsync("index.html"));
        app.Run();
    }

    static List<Message> ParseXML()
    {
        XmlDocument xDoc = new XmlDocument();
        xDoc.Load("data.xml");
        XmlElement? xRoot = xDoc.DocumentElement;
        List<Message> messages = new List<Message>();
        if (xRoot != null)
        {
            foreach (XmlElement xnode in xRoot)
            {
                var message = new Message();
                foreach (XmlNode childnode in xnode.ChildNodes)
                {
                    if (childnode.Name == "nickname")
                    {
                        message.Nickname = childnode.InnerText;
                    }
                    if (childnode.Name == "text")
                    {
                        message.Text = childnode.InnerText;
                    }
                }
                messages.Add(message);
            }
        }

        return messages;
    }

    static void AddData(string nick, string text)
    {
        XmlDocument xDoc = new XmlDocument();
        xDoc.Load("data.xml");
        XmlElement? xRoot = xDoc.DocumentElement;
 
        XmlElement messageElem = xDoc.CreateElement("message");
 
        XmlElement nickElem = xDoc.CreateElement("nickname");
        XmlElement textElem = xDoc.CreateElement("text");
 
        XmlText nameText = xDoc.CreateTextNode(nick);
        XmlText textText = xDoc.CreateTextNode(text);
 
        nickElem.AppendChild(nameText);
        textElem.AppendChild(textText);
 
        messageElem.AppendChild(nickElem);
        messageElem.AppendChild(textElem);
        xRoot?.AppendChild(messageElem);
        xDoc.Save("data.xml");
    }
}