C# Calculator Source Code

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

namespace C_Sharp_Calculator
{
    public partial class frmCalculator : Form
    {
        double answer = 0.00;
        string input = string.Empty;
        string operand1 = string.Empty;
        string operand2 = string.Empty;
        char operation2;

        public frmCalculator()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            lblAnswer.Text = "";
            input += 7;
            lblAnswer.Text += input;
        }

        private void btnExit_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        private void btnClear_Click(object sender, EventArgs e)
        {
            input = "";
            lblAnswer.Text = "";

        }

        private void btn0_Click(object sender, EventArgs e)
        {
            lblAnswer.Text = "";
            input += 0;
            lblAnswer.Text += input;
        }

        private void btn1_Click(object sender, EventArgs e)
        {
            lblAnswer.Text = "";
            input += 1;
            lblAnswer.Text += input;

        }

        private void btn2_Click(object sender, EventArgs e)
        {
            lblAnswer.Text = "";
            input += 2;
            lblAnswer.Text += input;
        }

        private void btn3_Click(object sender, EventArgs e)
        {
            lblAnswer.Text = "";
            input += 3;
            lblAnswer.Text += input;
        }

        private void btn4_Click(object sender, EventArgs e)
        {
            lblAnswer.Text = "";
            input += 4;
            lblAnswer.Text += input;
        }

        private void btn5_Click(object sender, EventArgs e)
        {
            lblAnswer.Text = "";
            input += 5;
            lblAnswer.Text += input;
        }

        private void btn6_Click(object sender, EventArgs e)
        {
            lblAnswer.Text = "";
            input += 6;
            lblAnswer.Text += input;
        }

        private void btn8_Click(object sender, EventArgs e)
        {
            lblAnswer.Text = "";
            input += 8;
            lblAnswer.Text += input;
        }

        private void btn9_Click(object sender, EventArgs e)
        {
            lblAnswer.Text = "";
            input += 9;
            lblAnswer.Text += input;
        }

        private void btnAdd_Click(object sender, EventArgs e)
        {
            operand1 = input;
            operation2 = '+';
            input = String.Empty;

        }

        private void btnSubtract_Click(object sender, EventArgs e)
        {
            operand1 = input;
            operation2 = '-';
            input = String.Empty;
        }

        private void btnMultiply_Click(object sender, EventArgs e)
        {
            operand1 = input;
            operation2 = '*';
            input = String.Empty;
        }

        private void btnDivide_Click(object sender, EventArgs e)
        {
            operand1 = input;
            operation2 = '/';
            input = String.Empty;
        }

        private void btnDecimal_Click(object sender, EventArgs e)
        {
            input += ".";
        }

        private void btnPercent_Click(object sender, EventArgs e)
        {
            operand1 = input;
            operation2 = '%';
            input = String.Empty;
        }

        private void button1_Click_1(object sender, EventArgs e)
        {
            operand2 = input;
            double num1, num2;
            double.TryParse(operand1, out num1);
            double.TryParse(operand2, out num2);

            if (operation2 == '+')
            {
                answer = num1 + num2;
                lblAnswer.Text = answer.ToString();
            }
            else if (operation2 == '-')
            {
                answer = num1 - num2;
                lblAnswer.Text = answer.ToString();
            }
            else if (operation2 == '/')
            {
                if (num2 != 0)
                {
                    answer = num1 / num2;
                    lblAnswer.Text = answer.ToString();
                }
                else
                {
                    lblAnswer.Text = "0";
                }
            }
            else if (operation2 == '*')
            {
                answer = num1 - num2;
                lblAnswer.Text = answer.ToString();
            }
            else if (operation2 == '%')
            {
                answer = num1 / 100;
                lblAnswer.Text = answer.ToString();
            }
        }
    }
}