MvvMAva/AvaloniaApplication4/ViewModels/Page2ViewModel.cs

using System;
using System.Collections.Generic;
using ReactiveUI;

using Avalonia.Media;
using Avalonia.Controls.Shapes;
using Avalonia.Threading;
using AvaloniaApplication4.Models;


using Avalonia.Controls;

using static System.Net.Mime.MediaTypeNames;
using Avalonia.Controls.Documents;


namespace AvaloniaApplication4.ViewModels
{
	public class Page2ViewModel : ReactiveObject
	{
        public  static List<string> funclis => Models.Model.funclist;

       public string _selectedFunclist = funclis[0];
        // ñâîéñòâî äëÿ îòîáðàæåíèÿ èçíà÷àëüíî âûáðàííîãî çíà÷åèÿ â ñïèñêå

        public List<String> Funclist 
        {
            get
            {
                return funclis;
            }
        }
        public string Selectedfunc
        {
           
            get => _selectedFunclist;
            set
            {
                this.RaiseAndSetIfChanged(ref _selectedFunclist, value);
                Calculate();
            }
        }

        double _num1;
        public double Num1
        {
            get => _num1;
            set => this.RaiseAndSetIfChanged(ref _num1, value);
        }

        double _num2;
        public double Num2
        {
            get => _num2;
            set => this.RaiseAndSetIfChanged(ref _num2, value);
        }
        string _symb;
        public string Symb
        {
            get => _symb;
            set => this.RaiseAndSetIfChanged(ref _symb, value);
        }
         string _result ="";
        public string Result
        {
            get => _result;
            set => this.RaiseAndSetIfChanged(ref _result, value);
        }
        double res = 0;
        public void Calculate()
        {
            if (Selectedfunc == "Ñëîæåíèå")
            {
                res = _num1 + _num2;
                Result = ""+res;
                Symb = "+";
            }
            if (Selectedfunc == "Äåëåíèå")
            {
                if (_num1 == 0 || _num2 == 0 || (_num2 == 0 && _num1 == 0))
                {
                    Result = "äåëåíèå íà íîëü";
                }
                else
                {
                    res = _num1 / _num2;
                    Result = "" + res;
                    Symb = "/";
                }
              
            }
            if (Selectedfunc == "Óìíîæåíèå")
            {
                res = _num1 * _num2;
                Result = "" + res;
                Symb = "*";
            }
            if (Selectedfunc == "Âû÷èòàíèå")
            {
                res = _num1 - _num2;
                Result = "" + res;
                Symb = "-";
            }
        }
    }
}