NewAuthAndCaptcha/AuthAndCaptcha/ViewModels/AuthViewModel.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using AuthAndCaptcha.Models;
using Avalonia.Controls;
using Avalonia.Controls.Shapes;
using Avalonia.Media;
using ReactiveUI;

namespace AuthAndCaptcha.ViewModels
{
	public class AuthViewModel : ReactiveObject
	{
        string usersLogin;
        string usersPassword;
        string canText;
        string canTextTrue;
        bool authButtonVisible = true;
        bool canTextVisible = false;

        public string UsersLogin { get => usersLogin; set => this.RaiseAndSetIfChanged(ref usersLogin, value); }
        public string UsersPassword { get => usersPassword; set => this.RaiseAndSetIfChanged(ref usersPassword, value); }
        public string CanText { get => canText; set => this.RaiseAndSetIfChanged(ref canText, value); }
        public string CanTextTrue { get => canTextTrue; set => this.RaiseAndSetIfChanged(ref canTextTrue, value); }
        public bool AuthButtonVisible { get => authButtonVisible; set => this.RaiseAndSetIfChanged(ref authButtonVisible, value); }
        public bool CanTextVisible { get => canTextVisible; set => this.RaiseAndSetIfChanged(ref canTextVisible, value); }

        Canvas can;
        public Canvas Can { get => can; set => this.RaiseAndSetIfChanged(ref can, value); }


        public void CreateCaptcha()
        {
            Random rnd = new Random();
            SolidColorBrush color = new SolidColorBrush(Color.FromRgb(Convert.ToByte(rnd.Next(256)), Convert.ToByte(rnd.Next(255)), Convert.ToByte(rnd.Next(255))));
            FontStyle[] fontStyles = new FontStyle[2] { FontStyle.Normal, FontStyle.Italic };
            FontWeight[] fontWeights = new FontWeight[2] { FontWeight.Normal, FontWeight.Bold };
            int dist = 10;

            Canvas canvas = new Canvas()
            {
                Width = 400,
                Height = 400,
                Background = color
            };

            int len = rnd.Next(7, 10);

            for (int i = 0; i < 20; i++)
            {
                SolidColorBrush colorLine = new SolidColorBrush(Color.FromRgb(Convert.ToByte(rnd.Next(256)), Convert.ToByte(rnd.Next(255)), Convert.ToByte(rnd.Next(255))));
                Line line = new Line()
                {
                    StartPoint = new Avalonia.Point(rnd.Next(400), rnd.Next(400)),
                    EndPoint = new Avalonia.Point(rnd.Next(400), rnd.Next(400)),
                    Stroke = colorLine,
                    StrokeThickness = 3,
                    
                };

                canvas.Children.Add(line);
            }

            for (int i = 0; i < len; i++)
            {
                FontStyle randomFontStyle = (FontStyle)rnd.Next(0, 3);

                string sym;
                int k = rnd.Next(0,2);
                if (k==0)
                {
                    sym = Convert.ToString((char)rnd.Next(48, 57));
                }
                else
                {
                    sym = Convert.ToString((char)rnd.Next(65, 90));
                }

                TextBlock text = new TextBlock()
                {
                    Text = sym,
                    FontSize = 20,
                    Foreground = Brushes.Black,
                    Margin = new Avalonia.Thickness(dist, rnd.Next(300), rnd.Next(300), 0),
                    FontStyle = fontStyles[rnd.Next(0, 2)],
                    FontWeight = fontWeights[rnd.Next(0, 2)]
                };
                canTextTrue = canTextTrue + Convert.ToString(text.Text);
                canvas.Children.Add(text);
                dist = dist + 35;
            }
            Debug.WriteLine(canTextTrue);
            Can = canvas;
        }
    }
}