C#

public partial class Calculator : System.Web.UI.Page
    {
        private int i, j;

        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void Button1_Click(object sender, EventArgs e)
        {

            MathClient client = new MathClient();


            try
            {
                int ii = client.Add(5, 6);
                Result.Text = Convert.ToString(ii);
            }
            catch (Exception ex)
            {
                Result.Text = ex.Message;
            }


        }

        protected void Button3_Click(object sender, EventArgs e)
        {
            int i, j;
            i = 4;
            j = 4;
        }

        protected void Button2_Click(object sender, EventArgs e)
        {
            int i, j = 4;
        }
    }

public string WMSCon_1 = "Data Source=172.178.1.120; initial Catalog=Sales_Master; User Id=codeproject; Password=xxxxxxx"

Rectangle re;
 private void form_MouseDown(object sender, MouseEventArgs e)
 {
     re.X = e.X;
     re.Y = e.Y;
     re.Width = 0;
     re.Height = 0;
 }

 private void form_MouseMove(object sender, MouseEventArgs e)
 {
     if (e.Button == MouseButtons.Left)
     {
         re.Width = e.X - re.X;
         re.Height = e.Y - re.Y;
         this.Invalidate();
     }
 }

 private void form_Paint(object sender, PaintEventArgs e)
 {
     SolidBrush myBrush;
     myBrush = new SolidBrush(Color.PaleTurquoise);
     e.Graphics.FillRectangle(myBrush, re);
 }

 private void Form1_Click(object sender, EventArgs e)
 {
     re = new Rectangle(0, 0, 0, 0);
     this.Invalidate();
 }