Error CS0118 'System.Windows' is a name but is used like a type

Witam.
To napisałem do dodawania:

 
       private void Dodawanie_Click(TextBox textbox, string value, System.Winows RoutedEventHandler) //Błąd niby jest na tej linijce
        {
            var originalNumber = double.Parse(textbox.Text);
            var numberToAdd = double.Parse(value);
            var sumOfNumbers = originalNumber + numberToAdd;
            textbox.Text = sumOfNumbers.ToString();
        } 

Wyskakuje mi :Error CS0118 'System.Windows' is a name but is used like a type
Co zrobić, żeby tego błędu nie było?

@john_klamka
Dzięki, ale teraz mam błąd :
Error CS0123 No overload for 'Dodawanie_Click' matches delegate 'RoutedEventHandler'

 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 A
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public delegate void RoutedEventHandler(
    object sender,
    RoutedEventArgs e
);
    public partial class MainWindow : Window
    {

        public MainWindow()
        {
            InitializeComponent();
        }
        int screen;
        double a;
        double result = 0;
        private void Odejmowanie_Click(object sender, RoutedEventArgs e)
        {
            a = double.Parse(TXB_2.Text);
            result -= a;
            TXB_1.Text = (result.ToString());
            TXB_2.Text = "";
        }

        private void Usuwanie_Click(object sender, RoutedEventArgs e)
        {
            TXB_1.Text = "";
        }

        private void B_1_Click(object sender, RoutedEventArgs e)
        {
            TXB_2.Text = TXB_2.Text + "1";
        }

        private void B_2_Click(object sender, RoutedEventArgs e)
        {
            TXB_2.Text = TXB_2.Text + "2";
        }

        private void B3_Click(object sender, RoutedEventArgs e)
        {
            TXB_2.Text = TXB_2.Text + "3";
        }

        private void B4_Click(object sender, RoutedEventArgs e)
        {
            TXB_2.Text = TXB_2.Text + "4";
        }
        private void B5_Click(object sender, RoutedEventArgs e)
        {
            TXB_2.Text = TXB_2.Text + "5";
        }

        private void B6_Click(object sender, RoutedEventArgs e)
        {
            TXB_2.Text = TXB_2.Text + "6";
        }

        private void B7_Click(object sender, RoutedEventArgs e)
        {
            TXB_2.Text = TXB_2.Text + "7";
        }

        private void B8_Click(object sender, RoutedEventArgs e)
        {
            TXB_2.Text = TXB_2.Text + "8";
        }

        private void B9_Click(object sender, RoutedEventArgs e)
        {
            TXB_2.Text = TXB_2.Text + "9";
        }

        private void B0_Click(object sender, RoutedEventArgs e)
        {
            TXB_2.Text = TXB_2.Text + "0";
        }

        private void ALEK_Click(object sender, EventArgs e)
        {
            Properties.Settings.Default.TXB_1 = TXB_1.Text;
            Properties.Settings.Default.Save();
        }

        private void AlEKL_Load(object sender, RoutedEventArgs e)
        {
            TXB_1.Text = Properties.Settings.Default.TXB_1;
        }


        private void Przeci_Click(object sender, RoutedEventArgs e)
        {
            TXB_2.Text = TXB_2.Text + ",";
        }

        private void Dodawanie_Click(TextBox textbox, string value, System.Windows.RoutedEventHandler eventHandler)
        {
            var originalNumber = double.Parse(textbox.Text);
            var numberToAdd = double.Parse(value);
            var sumOfNumbers = originalNumber + numberToAdd;
            textbox.Text = sumOfNumbers.ToString();
        }
    }
}

Mam ten kod:

 private void Dodawanie_Click(object sender, RoutedEventArgs e)
        {
            var originalNumber = double.Parse(textbox.Text);
            var numberToAdd = double.Parse(a.ToString()); //a to liczba którą wpiszemy do TXB_2
            var sumOfNumbers = originalNumber + numberToAdd;
            textbox.Text = sumOfNumbers.ToString();
            TXB_2.Text = ""; //czyści TXB_2 

Niby wszystko ok, nie ma błędów, ale kiedy włączam aplikację to nie chce się nic dodać. Kiedy mam liczbę "0" i wpiszę "5" i kliknę przycisk dodawania,to nic się nie stanie.
Dopiero kiedy kliknę "5" i odejmowanie zrobione innym sposobem będę miał wynik "-5". potem dodawanie działa normalnie, do momentu gdy wpiszę np."6" i kliknę przycisk dodawania. Program zamiast 6 dodaje dalej 5!
Co robić?