RegistryKey reg = Registry.CurrentUser.OpenSubKey("Control Panel\\Desktop");
 reg.SetValue("WallpaperStyle", "1");    //2 for stretch

 RegistryKey reg = Registry.CurrentUser.OpenSubKey("Control Panel\\Desktop", true);
 reg.SetValue("WallpaperStyle", "1");    //2 for stretch

 

public struct SystemTime
{
 public ushort Year;
 public ushort Month;
 public ushort DayOfWeek;
 public ushort Day;
 public ushort Hour;
 public ushort Minute;
 public ushort Second;
 public ushort Millisecond;
};

[DllImport("kernel32.dll", EntryPoint = "GetSystemTime", SetLastError = true)]
public extern static void Win32GetSystemTime(ref SystemTime st);

[DllImport("kernel32.dll", EntryPoint = "SetSystemTime", SetLastError = true)]
public extern static bool Win32SetSystemTime(ref SystemTime st);

....

public static void Test()
{
 SystemTime newTime = new SystemTime();
 newTime.Year = (ushort)2005;
 newTime.Month = (ushort)12;
 newTime.Day = (ushort)2;
 newTime.Hour = (ushort)12; //UTC time (if you are in UTC+2 zone then you'll put here: time - 2h)
 newTime.Minute = (ushort)42;
 newTime.Second = (ushort)11;
 Win32SetSystemTime(ref newTime);
}

public static void RemoveEmptyNodes(XmlDocument doc)
{
  XmlNodeList nodes = doc.SelectNodes("//node()");
            
  foreach (XmlNode node in nodes)
    if ((node.Attributes.Count == 0) && (node.ChildNodes.Count == 0))
      node.ParentNode.RemoveChild(node);
}

 string filename = "c:\\sample.htm";
 FileStream stream = new FileStream(filename, FileMode.Open, FileAccess.Read, 
 FileShare.None); //locks file

 ...

 stream.Close(); //unlocks file

 string filename = "c:\\sample.htm";
 FileStream stream = File.Open(filename, FileMode.Open);
 stream.Lock(0, stream.Length); //locks file

 ...

 stream.Unlock(0, stream.Length); //unlocks file

XmlNodeList list = xmlDoc.SelectNodes("//comment()");
foreach(XmlNode node in list)
  node.ParentNode.RemoveChild(node);

    public class CaptchaImage
    {
        // Public properties (all read-only).
        public string Text
        {
            get { return this.text; }
        }
        public Bitmap Image
        {
            get { return this.image; }
        }
        public int Width
        {
            get { return this.width; }
        }
        public int Height
        {
            get { return this.height; }
        }

        // Internal properties.
        private string text;
        private int width;
        private int height;
        private string familyName;
        private Bitmap image;

        // For generating random numbers.
        private Random random = new Random();

        // ====================================================================
        // Initializes a new instance of the CaptchaImage class using the
        // specified text, width and height.
        // ====================================================================
        public CaptchaImage(int length, int width, int height) : this(length, width, height, null)
        {
        }

        // ====================================================================
        // Initializes a new instance of the CaptchaImage class using the
        // specified text, width, height and font family.
        // ====================================================================
        public CaptchaImage(int length, int width, int height, string familyName)
        {
            this.text = GenerateRandomText(length);
            this.SetDimensions(width, height);
            this.SetFamilyName(familyName);
            this.GenerateImage();
        }

        private string GenerateRandomText(int length)
        {
            Random rnd = new Random();
            List<char> table = new List<char>();

            for (char i = 'A'; i <= 'Z'; i++)
                table.Add(i);

            for (char i = '0'; i <= '9'; i++)
                table.Add(i);

            string retVal = "";
            
            for (int i = 0; i < length; i++)
                retVal += table[rnd.Next(table.Count)];

            return retVal;
        }

        // ====================================================================
        // This member overrides Object.Finalize.
        // ====================================================================
        ~CaptchaImage()
        {
            Dispose(false);
        }

        // ====================================================================
        // Releases all resources used by this object.
        // ====================================================================
        public void Dispose()
        {
            GC.SuppressFinalize(this);
            this.Dispose(true);
        }

        // ====================================================================
        // Custom Dispose method to clean up unmanaged resources.
        // ====================================================================
        protected virtual void Dispose(bool disposing)
        {
            if (disposing)
                // Dispose of the bitmap.
                this.image.Dispose();
        }

        // ====================================================================
        // Sets the image width and height.
        // ====================================================================
        private void SetDimensions(int width, int height)
        {
            // Check the width and height.
            if (width <= 0)
                throw new ArgumentOutOfRangeException("width", width, "Argument out of range, must be greater than zero.");
            if (height <= 0)
                throw new ArgumentOutOfRangeException("height", height, "Argument out of range, must be greater than zero.");
            this.width = width;
            this.height = height;
        }

        // ====================================================================
        // Sets the font used for the image text.
        // ====================================================================
        private void SetFamilyName(string familyName)
        {
            // If the named font is not installed, default to a system font.
            try
            {
                Font font = new Font(this.familyName, 12F);
                this.familyName = familyName;
                font.Dispose();
            }
            catch (Exception ex)
            {
                this.familyName = System.Drawing.FontFamily.GenericSerif.Name;
            }
        }

        // ====================================================================
        // Creates the bitmap image.
        // ====================================================================
        private void GenerateImage()
        {
            // Create a new 32-bit bitmap image.
            Bitmap bitmap = new Bitmap(this.width, this.height, PixelFormat.Format32bppArgb);

            // Create a graphics object for drawing.
            Graphics g = Graphics.FromImage(bitmap);
            g.SmoothingMode = SmoothingMode.AntiAlias;
            Rectangle rect = new Rectangle(0, 0, this.width, this.height);

            // Fill in the background.
            HatchBrush hatchBrush = new HatchBrush(HatchStyle.SmallConfetti, Color.LightGray, Color.White);
            g.FillRectangle(hatchBrush, rect);

            // Set up the text font.
            SizeF size;
            float fontSize = rect.Height + 1;
            Font font;
            // Adjust the font size until the text fits within the image.
            do
            {
                fontSize--;
                font = new Font(this.familyName, fontSize, FontStyle.Bold);
                size = g.MeasureString(this.text, font);
            } while (size.Width > rect.Width);

            // Set up the text format.
            StringFormat format = new StringFormat();
            format.Alignment = StringAlignment.Center;
            format.LineAlignment = StringAlignment.Center;

            // Create a path using the text and warp it randomly.
            GraphicsPath path = new GraphicsPath();
            path.AddString(this.text, font.FontFamily, (int)font.Style, font.Size, rect, format);
            float v = 4F;
            PointF[] points =
			{
				new PointF(this.random.Next(rect.Width) / v, this.random.Next(rect.Height) / v),
				new PointF(rect.Width - this.random.Next(rect.Width) / v, this.random.Next(rect.Height) / v),
				new PointF(this.random.Next(rect.Width) / v, rect.Height - this.random.Next(rect.Height) / v),
				new PointF(rect.Width - this.random.Next(rect.Width) / v, rect.Height - this.random.Next(rect.Height) / v)
			};
            Matrix matrix = new Matrix();
            matrix.Translate(0F, 0F);
            path.Warp(points, rect, matrix, WarpMode.Perspective, 0F);

            // Draw the text.
            hatchBrush = new HatchBrush(HatchStyle.LargeConfetti, Color.LightGray, Color.DarkGray);
            g.FillPath(hatchBrush, path);

            // Add some random noise.
            int m = Math.Max(rect.Width, rect.Height);
            for (int i = 0; i < (int)(rect.Width * rect.Height / 30F); i++)
            {
                int x = this.random.Next(rect.Width);
                int y = this.random.Next(rect.Height);
                int w = this.random.Next(m / 50);
                int h = this.random.Next(m / 50);
                g.FillEllipse(hatchBrush, x, y, w, h);
            }

            // Clean up.
            font.Dispose();
            hatchBrush.Dispose();
            g.Dispose();

            // Set the image.
            this.image = bitmap;
        }
    }

 webBrowser1.Navigate("about:blank");
 webBrowser1.Document.Write("<html><body><h1>Hello World!</h1></body></html>");

using System;
using System.Collections.Generic;
using System.Text;
using System.Threading;

namespace ConsoleApplication12
{
    class Program
    {
        static object thisLock = new object();
        static int z = 0;
        private static void ThrStart()
        {
            for (int i = 0; i < 10000; i++)
            {
                lock (thisLock)
                {
                    z++;
                    Console.WriteLine(z);
                }
            }
        }

        private static void ThrStart2()
        {
            for (int i = 0; i < 10000; i++)
            {
                Monitor.Enter(thisLock);
                z++;
                Console.WriteLine(z);
                Monitor.Exit(thisLock);
            }
        }

        static Mutex mutex = new Mutex();
        private static void ThrStart3()
        {
            for (int i = 0; i < 10000; i++)
            {
                mutex.WaitOne();
                z++;
                Console.WriteLine(z);
                mutex.ReleaseMutex();
            }
        }


        static void Main(string[] args)
        {
            Thread t1 = new Thread(new ThreadStart(ThrStart));
            Thread t2 = new Thread(new ThreadStart(ThrStart));
            t1.Start();
            t2.Start();
            t1.Join();
            t2.Join();

            t1 = new Thread(new ThreadStart(ThrStart2));
            t2 = new Thread(new ThreadStart(ThrStart2));
            t1.Start();
            t2.Start();
            t1.Join();
            t2.Join();

            t1 = new Thread(new ThreadStart(ThrStart3));
            t2 = new Thread(new ThreadStart(ThrStart3));
            t1.Start();
            t2.Start();
            t1.Join();
            t2.Join();
        }
    }
}

this.PointToScreen(this.Label1.Location)

 public class CRC32
 { //"123456789" -> 0xCBF43926
  #region crctab
  private static readonly UInt32[] crctab =
   {
    0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
    0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
    0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
    0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
    0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
    0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
    0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
    0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
    0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
    0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
    0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
    0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
    0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
    0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
    0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
    0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
    0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
    0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
    0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
    0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
    0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
    0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
    0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
    0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
    0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
    0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
    0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
    0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
    0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
    0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
    0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
    0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
    0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
    0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
    0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
    0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
    0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
    0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
    0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
    0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
    0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
    0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
    0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
    0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
    0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
    0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
    0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
    0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
    0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
    0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
    0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
    0x2d02ef8d
   };
  #endregion
  public static byte[] Calculate(byte[] what)
  {
   UInt32 crc = 0xffffffff;
   for (int i = 0; i < what.Length; i++)
    crc = (crc >> 8) ^ crctab[(crc & 0xff) ^ what[i]];
   crc ^= 0xffffffff;
   byte[] output = new byte[4];
   
   output[0] = (byte)(crc >> 24);
   output[1] = (byte)(crc >> 16);
   output[2] = (byte)(crc >> 8);
   output[3] = (byte)(crc);
   
   return output;
  }
 }