Unlucky calculator

using System;
using System.Windows.Forms;
using System.Drawing;


public class win : Form
{

    Button[] b = new Button[10];
    Button bDot, bPlus, bSub, bMul, bDiv, bEqu, bClr;
    Panel panCalc;
    TextBox txtCalc;

    Double dblAcc;
    Double dblSec;
    bool blnClear, blnFrstOpen;
    String strOper;

    public win()
    {
        try
        {
            this.Text = "Calculator";
            panCalc = new Panel();
            txtCalc = new TextBox();

            txtCalc.Location = new Point(10, 10);
            txtCalc.Size = new Size(150, 10);
            txtCalc.ReadOnly = true;
            txtCalc.RightToLeft = RightToLeft.Yes;
            panCalc.Size = new Size(200, 200);
            panCalc.BackColor = Color.Aqua;
            panCalc.Controls.Add(txtCalc);
            addButtons(panCalc);
            this.Size = new Size(200, 225);
            this.Controls.Add(panCalc);

            dblAcc = 0;
            dblSec = 0;
            blnFrstOpen = true;
            blnClear = false;
            strOper = new String('=', 1);
        }
        catch (Exception e)
        {
            Console.WriteLine("error ......  " + e.StackTrace);
        }
    }

    private void addButtons(Panel p)
    {
        for (int i = 0; i <= 9; i++)
        {
            b[i] = new Button();
            b[i].Text = Convert.ToString(i);
            b[i].Size = new Size(25, 25);
            b[i].BackColor = Color.White;
            b[i].Click += new EventHandler(btn_clk);
            p.Controls.Add(b[i]);
        }
        b[0].Location = new Point(10, 160);
        b[1].Location = new Point(10, 120);
        b[4].Location = new Point(10, 80);
        b[7].Location = new Point(10, 40);

        b[2].Location = new Point(50, 120);
        b[5].Location = new Point(50, 80);
        b[8].Location = new Point(50, 40);

        b[3].Location = new Point(90, 120);
        b[6].Location = new Point(90, 80);
        b[9].Location = new Point(90, 40);

        bDot = new Button();
        bDot.Size = new Size(25, 25);
        bDot.Location = new Point(50, 160);
        bDot.BackColor = Color.White;
        bDot.Text = ".";
        bDot.Click += new EventHandler(btn_clk);

        bPlus = new Button();
        bPlus.Size = new Size(25, 25);
        bPlus.Location = new Point(130, 160);
        bPlus.BackColor = Color.White;
        bPlus.Text = "+";
        bPlus.Click += new EventHandler(btn_Oper);

        bSub = new Button();
        bSub.Size = new Size(25, 25);
        bSub.Location = new Point(130, 120);
        bSub.BackColor = Color.White;
        bSub.Text = "-";
        bSub.Click += new EventHandler(btn_Oper);

        bMul = new Button();
        bMul.Size = new Size(25, 25);
        bMul.Location = new Point(130, 80);
        bMul.BackColor = Color.White;
        bMul.Text = "*";
        bMul.Click += new EventHandler(btn_Oper);

        bDiv = new Button();
        bDiv.Size = new Size(25, 25);
        bDiv.Location = new Point(130, 40);
        bDiv.BackColor = Color.White;
        bDiv.Text = "/";
        bDiv.Click += new EventHandler(btn_Oper);

        bEqu = new Button();
        bEqu.Size = new Size(25, 25);
        bEqu.Location = new Point(90, 160);
        bEqu.BackColor = Color.White;
        bEqu.Text = "=";
        bEqu.Click += new EventHandler(btn_equ);

        bClr = new Button();
        bClr.Size = new Size(20, 45);
        bClr.Location = new Point(170, 40);
        bClr.BackColor = Color.Orange;
        bClr.Text = "AC";
        bClr.Click += new EventHandler(btn_clr);

        p.Controls.Add(bDot);
        p.Controls.Add(bPlus);
        p.Controls.Add(bSub);
        p.Controls.Add(bMul);
        p.Controls.Add(bDiv);
        p.Controls.Add(bEqu);
        p.Controls.Add(bClr);
    }

    private void btn_clk(object obj, EventArgs ea)
    {
        if (blnClear)
            txtCalc.Text = "";

        Button b3 = (Button)obj;

        txtCalc.Text += b3.Text;

        if (txtCalc.Text == ".")
            txtCalc.Text = "0.";
        dblSec = Convert.ToDouble(txtCalc.Text);

        blnClear = false;
    }

    private static void Main()
    {
        Application.Run(new win());
    }

    private void btn_Oper(object obj, EventArgs ea)
    {
        Button tmp = (Button)obj;
        strOper = tmp.Text;
        if (blnFrstOpen)
            dblAcc = dblSec;
        else
            calc();

        blnFrstOpen = false;
        blnClear = true;
    }

    private void btn_clr(object obj, EventArgs ea)
    {
        clear();
    }

    private void btn_equ(object obj, EventArgs ea)
    {
        calc();

    }

    private void calc()
    {

        switch (strOper)
        {

            case "+":
                dblAcc += dblSec;
                break;
            case "-":
                dblAcc -= dblSec;
                break;
            case "*":
                dblAcc *= dblSec;
                break;
            case "/":
                dblAcc /= dblSec;
                break;
        }

        strOper = "=";
        blnFrstOpen = true;
        txtCalc.Text = Convert.ToString(dblAcc);
        dblSec = dblAcc;
    }

    private void clear()
    {
        dblAcc = 0;
        dblSec = 0;
        blnFrstOpen = true;
        txtCalc.Text = "";
        txtCalc.Focus();

    }
}