How can I perform 1+2+3*4/5 in xamarin form calculator

        string Operand1 = "";
        bool isoperatorselected=false; 
        private void Button_Clicked(object sender, EventArgs e)
        {
            var Button =  (Button) sender;
            string Input = Button.Text;
            if (isoperatorselected)
            {
                Operand1 = Operand1 + Input;
                resultText.Text = Operand1;
            }
           else
            {
                Operand2 =  Input;
               resultText.Text = Operand2;
          }
        }
        private void Operator_Clicked(object sender, EventArgs e)
        {
            var Button = (Button)sender;
            string Input = Button.Text;
            isoperatorselected = true;
            if ("+"==Input)
            {
                Operator = "+";
            }
            else if ("-"==Input)
            {
                Operator = "-";
            }
            else if ("*"==Input)
            {
                Operator = "*";
            }
            else if ("/"==Input)
            {
                Operator = "/";
            }
        }
        private void Clear_Clicked(object sender, EventArgs e)
        {
            this.resultText.Text = "";
            this.Input = string.Empty;
            this.Operand1 = string.Empty;
            this.Operand2 = string.Empty;

        }
        private void Equal_Clicked(object sender, EventArgs e)
        {
            Operand2 = Input;
            double FirstNumber;
            double SecondNumber;
            double.TryParse(Operand1, out FirstNumber);
            double.TryParse(Operand1, out SecondNumber);

            if (Operator=="+")
            {
                result = FirstNumber + SecondNumber;
                resultText.Text = result.ToString();
            }
            else if(Operator=="-")
            {
                result = FirstNumber - SecondNumber;
                resultText.Text = result.ToString();
            }
            else if(Operator=="*")
            {
                result = FirstNumber * SecondNumber;
                resultText.Text = result.ToString();
            }
            else if(Operator=="/")
            {
                if(SecondNumber!=0)
                {
                    result = FirstNumber / SecondNumber;
                    resultText.Text = result.ToString();
                }
            }
        }
    }
}