public void Div()
        {
            sp = new SimpleCalculatorService ();
            double result = sp.Div(9,3);
            Assert.AreEqual (3, result);

            result = sp.Div(9,0);
            Assert.AreEqual (0, result);
        }
 public void Summ()
 {
     sp = new SimpleCalculatorService ();
     double result = sp.Summ(4,4);
     Assert.AreEqual (8, result);
 }
 public void Multi()
 {
     sp = new SimpleCalculatorService ();
     double result = sp.Multi(2,5);
     Assert.AreEqual (10, result);
 }
 public void Diff()
 {
     sp = new SimpleCalculatorService ();
     double result = sp.Diff(9,4);
     Assert.AreEqual (5, result);
 }
        //В зависимости от входящей операции производятся арифметические действия
        public void ArithmeticOperations(string operation)
        {
            if (Value == 0)
                Value = Convert.ToDouble (InputString);

            //Проверка на нажатие кнопки с цифрой и реализация арифметических операций
            if (Button_pressed == true){
                switch (s_Operation){

                case "+":
                    Button_pressed = false;
                    Value = new SimpleCalculatorService ().Summ (Value, Convert.ToDouble (InputString));
                    //Value = DependencyService.Get<ICalculatorService> ().Summ (Value, Convert.ToDouble (InputString));
                    InputString = Convert.ToString (Value);
                    break;
                case "-":
                    Button_pressed = false;
                    Value = DependencyService.Get<ICalculatorService> ().Diff (Value, Convert.ToDouble (InputString));
                    InputString = Convert.ToString (Value);
                    break;
                case "*":
                    Button_pressed = false;
                    Value = DependencyService.Get<ICalculatorService> ().Multi (Value, Convert.ToDouble (InputString));
                    InputString = Convert.ToString (Value);
                    break;
                case "/":
                    Button_pressed = false;
                    if (InputString == "0")
                        InputString = "На ноль делить нельзя!";
                    else {
                        Value = DependencyService.Get<ICalculatorService> ().Div (Value, Convert.ToDouble (InputString));
                        InputString = Convert.ToString (Value);
                    }
                    break;
                default:
                    Button_pressed = false;
                    break;
                }
            }

            if (operation == "="){
                if (InputString != "На ноль делить нельзя!")
                    InputString = Convert.ToString (Value);
                else {
                    Value = 0;
                    s_Operation = "";
                }
            }
            else
                s_Operation = operation;

            DisplayText = InputString;
        }