Winform Calc

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 Calculator3
{
    public partial class Calculator : Form
    {
        public Calculator()
        {
            InitializeComponent();
        }

        private void Calculator_Load(object sender, EventArgs e)
        {

        }

        private void btn0_Click(object sender, EventArgs e)
        {

        }

        private void btn1_Click(object sender, EventArgs e)
        {

        }

        private void btn2_Click(object sender, EventArgs e)
        {

        }

        private void btn3_Click(object sender, EventArgs e)
        {

        }

        private void btn4_Click(object sender, EventArgs e)
        {

        }

        private void btn5_Click(object sender, EventArgs e)
        {

        }

        private void btn6_Click(object sender, EventArgs e)
        {

        }

        private void btn7_Click(object sender, EventArgs e)
        {

        }

        private void btn8_Click(object sender, EventArgs e)
        {

        }

        private void btn9_Click(object sender, EventArgs e)
        {

        }

        private void btnDot_Click(object sender, EventArgs e)
        {

        }

        private void numPad_Click(object sender, EventArgs e)
        {
            Button btn = (Button)sender;
            string num = btn.Text;

            string temp = txtResults.Text;
            if (flagOpPressed == true)
            {
                temp = "";
                flagOpPressed = false;
            }
            switch (num)
            {
                case ".":
                    if (!temp.Contains("."))
                    {
                        temp += ".";
                    }
                    break;
                default:
                    if (temp == "0")
                        temp = "";
                    temp += num;
                    break;
            }
            txtResults.Text = temp;
        }

        string opr = "";
        double operand = 0;
        private void btnEqu_Click(object sender, EventArgs e)
        {

            double value = Double.Parse(txtResults.Text);
            switch (opr)
            {
                case "Add":
                    operand = operand + value;
                    txtResults.Text = operand.ToString();
                    break;
                default:
                    operand = value;
                    break;
                case "sub":
                    operand = operand - value;
                    txtResults.Text = operand.ToString();
                    break;
                case "Sqr":
                    operand = operand * operand;
                    txtResults.Text = operand.ToString();
                    break;
                case "Times":
                    operand = operand * value;
                    txtResults.Text = operand.ToString();
                    break;
                case "Div":
                    operand = operand / value;
                    txtResults.Text = operand.ToString();
                    break;
                case "1/x":
                    operand = 1 / value;
                    txtResults.Text = operand.ToString();
                    break;



            }
        }

        bool flagOpPressed = false;
        private string calcFunc;

        private void operator_Click(object sender, EventArgs e)
        {
            btnEqu.PerformClick();
            operand = Double.Parse(txtResults.Text);

            Button btn = (Button)sender;
            opr = btn.Tag.ToString();
            flagOpPressed = true;
        }

        private void btnCE_Click(object sender, EventArgs e)
        {
            opr = "";
            operand = 0;
            flagOpPressed = false;
            txtResults.Text = "";
        }

        private void u_operatorClick(object sender, EventArgs e)
        {
            Button btn = (Button)sender;
            string u_opr = btn.Tag.ToString();


            double value = Double.Parse(txtResults.Text);
            string results;
            switch (u_opr)
            {
                case "Sqrt":
                    results = Math.Sqrt(value).ToString("N10");
                    txtResults.Text = results.TrimEnd('0').TrimEnd('.');
                    break;
                case "Log":
                    results = Math.Log10(value).ToString("N10");
                    txtResults.Text = results.TrimEnd('0').TrimEnd('.');
                    break;
                case "p10":
                    results = Math.Pow(10, value).ToString("N10");
                    txtResults.Text = results.TrimEnd('0').TrimEnd('.');
                    break;
                case "Sin":
                    results = Math.Sin(value).ToString("N10");
                    txtResults.Text = results.TrimEnd('0').TrimEnd('.');
                    break;
                case "Cos":
                    results = Math.Cos(value).ToString("N10");
                    txtResults.Text = results.TrimEnd('0').TrimEnd('.');
                    break;
                case "Tan":
                    results = Math.Tan(value).ToString("N10");
                    txtResults.Text = results.TrimEnd('0').TrimEnd('.');
                    break;
                case "Exp":
                    results = Math.Exp(value).ToString("N10");
                    txtResults.Text = results.TrimEnd('0').TrimEnd('.');
                    break;
                case "ln":
                    results = Math.l(value).ToString("N10");
                    txtResults.Text = results.TrimEnd('0').TrimEnd('.');
                    break;




            }
        }

        private void btnCLR_Click(object sender, EventArgs e)
        {
            txtResults.Text = string.Empty;
            operand = 0;
            operand = 0;
            calcFunc = string.Empty;
            flagOpPressed = false;
        }
    }
}