using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms;

namespace WindowsFormsApplication2 { public partial class Form1 : Form { double anfangszahl; double result; double zweitzahl; bool buttonclicked = true; bool reset = true;

    public Form1()
    {
        InitializeComponent();
    }

    private void btn_button(object sender, EventArgs e)
    {
        Button scalar = (sender as Button);
        txt_display.Text += scalar.Text;
        double.TryParse(scalar.Text, out anfangszahl);           
    }

    private void btn_operator(object sender, EventArgs e)
    {
        Button operat = (sender as Button);
        string operatorsymbol = operat.Text;
        switch (operatorsymbol)
        {
            case "+":
                result = anfangszahl + anfangszahl;
                break;
            case "-":
                result = anfangszahl - anfangszahl;
                break;
            case "*":
                result = anfangszahl * anfangszahl;
                break;
            case "/":
                result = anfangszahl / anfangszahl;
                break;
        }
    }

    private void btn_equal_Click(object sender, EventArgs e)
    {
         txt_display.Text = result.ToString();
    }
}

} das ist der ganze src code

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