C#

I have a program I am working on. First I will explain what I have done and then get to the question. I have created a undo and redo functions that when undo, it deletes one character at a time from the string and puts it in a 'List<char>'. Then when you click redo, it goes to the 'List' and adds each character back to the string and deletes it from the list, one character at a time. You can see in the pictures the undo and redo menu button click events for them in the 1st pic. They get their functions from the 2nd pic., the undo redo class. I also have a keydown and text change function shown in pic. 3. All functions work good but the clearing of the 'list' that remains if they don't 'redo' all commands. I can undo and redo and have no problems, but I want it to delete the list contents after the user starts to type again after undoing and redoing. I have tried to put it in the text change but it keeps firing every time the list is over '0' and after the menu redo is enabled. I have tried putting in the buttons function, and I even tried to do the stack<char> process, but I could not get my head wrapped around that option. I know that 'richTxtDirections.Text = richTxtDirections.Text.Remove(richTxtDirections.Text.Length - 1);' deletes 1 character, but how do you say if the 'text.length +1' from where you stop to undo and redo, how to add a character. I hope I am explaining this fine for you to understand and that someone can possibly help me with this part, even if it is not adding 1 to the text.length. Thank you.

private void menuUndoEdit_Click(object sender, EventArgs e)
        {
            menuUndoEditClicked = true;

            //accesses the undo function to undo last command
            UndoRedo.undo();

            if (richTxtDirections.Text.Length > 0)
            {
                //removes the last character in the text in the textbox
                richTxtDirections.Text = richTxtDirections.Text.Remove(richTxtDirections.Text.Length - 1);

                //positions the cursor at the end of the text
                richTxtDirections.Select(richTxtDirections.Text.Length, 0);
            }

            //condition for menu redo edit button is enabled
            if (menuRedoEdit.Enabled == false)
            {
                //if the keys (control and Z) are pressed enables the redo button...
                menuRedoEdit.Enabled = true;
                //sets the font to specified font and style to regular....
                menuRedoEdit.Font = new Font(menuRedoEdit.Font, FontStyle.Regular);
                //sets the color to black...
                menuRedoEdit.ForeColor = Color.Black;
                //sets the button text to redo
                menuRedoEdit.Text = "Redo";
            }
            menuUndoEditClicked = false;
        }


private void menuRedoEdit_Click(object sender, EventArgs e)
        {
            menuRedoEditClicked = true;

            UndoRedo.redo();
            
            if (UndoRedo.charList.Count == 0)
            {
                menuRedoEdit.Enabled = false;
                menuRedoEdit.Font = new Font(menuRedoEdit.Font, FontStyle.Italic);
                menuRedoEdit.ForeColor = Color.DarkGray;
                menuRedoEdit.Text = "Can't Redo";
            }

            menuRedoEditClicked = false;

            richTxtDirections.Focus();
        }


private void richTxtDirections_KeyDown(object sender, KeyEventArgs e)
        {
            //adding a character count to show the user how many was put in and that they can only go to what is max.
            lblCount2.Text = richTxtDirections.Text.Length + "/750";

            //condition to see if rich textbox directions is empty or not
            if (richTxtDirections.Focused == true && richTxtDirections.Text != string.Empty)
            {
                if (menuUndoEdit.Enabled == false)
                {
                    //when there is a change in the textbox, undo button is enabled
                    menuUndoEdit.Enabled = true;

                    //changes the font to regular and whatever font specified
                    menuUndoEdit.Font = new Font(menuUndoEdit.Font, FontStyle.Regular);

                    //changes the font color to normal
                    menuUndoEdit.ForeColor = Color.Black;
                }

                //condition where rich textbox is not empty and checks to see if 'z' key was pressed.
                if (e.KeyCode == Keys.Z && (e.Control))
                {
                    e.Handled = true;

                    menuUndoEdit.PerformClick();
                }

                //condition where rich textbox is not empty and checks to see if 'y' key was pressed.
                else if (e.KeyCode == Keys.Y && e.Control)
                {
                    e.Handled = true;

                    menuRedoEdit.PerformClick();
                }
            }
        }

        private void richTxtDirections_TextChanged(object sender, EventArgs e)
        {
            if (UndoRedo.charList.Count > 0 && menuRedoEditClicked == false)
            {
                UndoRedo.clearList();
            }
        }


public void undo()
        {
            //condition to see if rich textbox directions has text in it.
            if (frmDashboard.instance.tbrdDirections.Text.Length > 0)
            {
                //adding the characters in the string that is in the textbox text to the list
                charList.Add(frmDashboard.instance.tbrdDirections.Text[frmDashboard.instance.tbrdDirections.Text.Length - 1]);
            }
        }

        public void redo()
        {
            //condition to see if the list has anything stored in it
            if (charList.Count > 0)
            {
                //creating a variable to store the list
                var lastItem = charList.Last();

                //appending the characters to the end of directions textbox text
                frmDashboard.instance.tbrdDirections.AppendText(lastItem.ToString());

                //removing the character from the list
                charList.RemoveAt(charList.Count - 1);
            }
        }

        public void clearList()
        {
            //condition to see if the list has anything stored in it
            if (charList.Count > 0)
            {
                //if the list has stored unused items left in it, it clears the list.
                charList.Clear();

                //since there is nothing to redo on the form, it disables the redo button
                frmDashboard.instance.mnuRedoEdit.Enabled = false;
            }
        }

I have this class User:

    [Serializable()]
    [XmlRoot("Users")]
    public class Users
    {
        [XmlArrayItem(typeof(User))]
        public List<User> UsersList { get; set; }
    }


    [Serializable()]
    public class User
    {
        [System.Xml.Serialization.XmlAttribute("ID")]
        public string ID { get; set; }

        [System.Xml.Serialization.XmlElementAttribute("Name")]
        public string Name { get; set; }

        [System.Xml.Serialization.XmlElementAttribute("Username")]
        public string Username { get; set; }

        [System.Xml.Serialization.XmlElementAttribute("Password")]
        public string Password { get; set; }

        [System.Xml.Serialization.XmlElementAttribute("Email")]
        public string Email { get; set; } = string.Empty;
    }
	
	
And this:
  private void Serialization()
        {
            var path = @"D:\Projects\repo\xml\users.xml";
            var newUsers = new Users();
            newUsers.UsersList = new List<User>();
            
                var user = new User
                ();
                user.Email = txtEmail.Text;
                user.Name = txtName.Text;
                user.Password = txtPass.Text;
                user.ID =txtID.Text;
                newUsers.UsersList.Add(user);

            XmlSerializer serializer = new XmlSerializer(typeof(Users));
            using (TextWriter writer =  new StreamWriter(path,true))
            {
                serializer.Serialize(writer, newUsers);
            }
        }

And it saves this xml:


<?xml version="1.0" encoding="utf-8"?>
<Users xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
	<UsersList>
		<User ID="A">
			<Name>a</Name>
			<Password>a</Password>
			<Email>a</Email>
		</User>
	</UsersList>
</Users><?xml version="1.0" encoding="utf-8"?>
<Users xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
	<UsersList>
		<User ID="SSSS">
			<Name>s</Name>
			<Password>s</Password>
			<Email>ss</Email>
		</User>
	</UsersList>
</Users>


But I want to save the xml file in this format:

<?xml version="1.0" encoding="utf-8"?>
<Users xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
	<UsersList>
		<User ID="A">
			<Name>a</Name>
			<Password>a</Password>
			<Email>a</Email>
		</User>
		<User ID="SSSS">
			<Name>s</Name>
			<Password>s</Password>
			<Email>ss</Email>
		</User>
	</UsersList>
The most important thing is that I have a windows form with some textboxes and every time I run the application and register a new user I want it to pe added in <UsersList> not overwritten over the existing ones

<pre lang="C#">

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using Numpy;
using Python.Runtime;
using Keras;
using Keras.Layers;
using Keras.Models;
using Keras.Optimizers;
using Keras.losses;

namespace SQLInjectionDetection
{
    class Program
    {
        static void Main(string[] args)
        {
            // Load CSV file
            var trainData = File.ReadAllLines("tokens.csv")
                .Select(l => l.Split(','))
                .Select(s => new { Token = s[0], Label = int.Parse(s[1]) })
                .ToList();

            // Shuffle trainData
            var random = new Random();
            trainData = trainData.OrderBy(d => random.Next()).ToList();

            // Split trainData into training and validation sets
            var splitIndex = (int)(trainData.Count * 0.8);
            var trainDataSubset = trainData.Take(splitIndex).ToList();
            var testDataSubset = trainData.Skip(splitIndex).ToList();

            // Define vocabulary and tokenize trainData
            var vocabulary = new HashSet<char>(trainDataSubset.SelectMany(d => d.Token).Distinct());
            var tokenToIndex = vocabulary.Select((c, i) => new { Token = c, Index = i }).ToDictionary(t => t.Token, t => t.Index);
            var maxSequenceLength = trainDataSubset.Max(d => d.Token.Length);
            var trainTokenized = Tokenize(trainDataSubset, tokenToIndex, maxSequenceLength);
            var testTokenized = Tokenize(testDataSubset, tokenToIndex, maxSequenceLength);

            // Build RNN model
            using (Py.GIL())
            {
                dynamic keras = Py.Import("keras");
                dynamic np = Py.Import("numpy");
                var input = new Input(shape: 1000);
                var embedding = new Embedding(vocabulary.Count, 32).Apply(input);
                var lstm = new LSTM(32).Apply(embedding);
                var output = new Dense(1, activation: keras.activations.sigmoid).Apply(lstm);
                var model = new Model(inputs: input, outputs: output);
                model.Compile(optimizer: new Adam(), loss: new BinaryCrossentropy(), metrics: new[] { "accuracy" });

                // Train model
                var trainX = trainTokenized.Item1;
                var trainY = trainTokenized.Item2;
                var testX = testTokenized.Item1;
                var testY = testTokenized.Item2;
                model.Fit(trainX, trainY, batchSize: 32, epochs: 10, validationData: (testX, testY));

                // Take user input and make prediction
                Console.Write("Enter user input: ");
                var userInput = Console.ReadLine();
                var inputTokenized = TokenizeInput(userInput, tokenToIndex, maxSequenceLength);
                var prediction = model.Predict(inputTokenized).GetData<float>()[0, 0];
                Console.WriteLine($"Prediction: {(prediction > 0.5 ? "Malicious" : "Safe")} (Score: {prediction:F4})");

                // Evaluate model
                var testMetrics = model.Evaluate(testX, testY);
                Console.WriteLine($"Test loss: {testMetrics[0]:F4}");
                Console.WriteLine($"Test accuracy: {testMetrics[1]:F4}");
            }
        }

        private static (NDarray, NDarray) Tokenize(List<dynamic> data, Dictionary<char, int> tokenToIndex, int maxSequenceLength)
        {
            var numExamples = data.Count;
            var X = np.zeros((numExamples, maxSequenceLength));
            var Y = np.zeros((numExamples, 1));
            for (var i = 0; i < numExamples; i++)
            {
                var tokens = data[i].Token;
                var label = data[i].Label;
                Y[i] = label;
                for (var j = 0; j < tokens.Length; j++)
                {
                    var token = tokens[j];
                    var index = tokenToIndex[token];
                    X[i, j] = index;
                }
            }
            return (X, Y);
        }

    }
}