stack

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace Opgave7._7
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        string click = string.Empty;
        string operand1 = string.Empty;
        string operand2 = string.Empty;
        char operation;
        int resultaat = 0;

        private void btnNumber(object sender, RoutedEventArgs e)
        {
            var button = (Button)sender;
            this.click += (string)button.Content;

            txbInput.Text= click;
        }

        private void btnPlus(object sender, RoutedEventArgs e)
        {
            var button = (Button)sender;
            this.operation = (Convert.ToChar("+"));
        }

        private void btnMinus(object sender, RoutedEventArgs e)
        {
            var button = (Button)sender;
            this.operation = (Convert.ToChar("-"));
            
        }

        private void btnEquals(object sender, RoutedEventArgs e)
        {
            var button = (Button)sender;
            this.operation = (Convert.ToChar("="));
            //if statement char
        }

        private void btnClear(object sender, RoutedEventArgs e)
        {
            click = "";
        }
    }
}