Singleton Class Uses and Drawbacks

Singleton :-
Singleton is controversial design pattern of OOPS. It allows you to restrict the number of instances of an object.It's an interface that allows a class to enforce that it is only allocated once.

Sample Code :-

Namespace :-
using system.text;
using System.collections;

class SampleProgram
{
public static void Main()
{
SingletonStructure singleton = SingletonStructure.Instance;
}
}

public sealed class SingletonStructure
{
static readonly SingletonStructure _instance = new SingletonStructure();
public static SingletonStructure Instance
{
get
{
return _instance;
}
}
Constructor which will be initialize and create the instance
SingletonStructure()
{
// Initialize.
}
}

Null check singleton: 435 ms
Optimized singleton : 42 ms (As Above)

This method is fast beacause instance member is created directly in its declaration

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How to read XML Node using C#

Load an XML File

XmlDocument xdXml = new XmlDocument();
xdXml.Load("Index.xml");

Make a nodelist
XmlNodeList xnNodes = xdXml.SelectNodes("/Tools/Download");

Walk through the list
foreach (XmlNode node in xnNodes)
{
if (node.FirstChild.InnerText == ddlTools.Text)
{
//Get all the child nodes
XmlNodeList childNodes = node.ChildNodes;

//And walk through them
foreach (XmlNode child in childNodes)
{
//Check which node we have now
switch (child.Name)
{
case "Name":
txtName.Text = child.InnerText;
break;
case "Version":
txtVersion.Text = child.InnerText;
break;
case "Category":
txtCategory.Text = child.InnerText;
break;
case "Description":
txtDescription.Text = child.InnerText;
break;
}
}
childNodes = null;
break;
}
}

Clean up
xdXml = null;
xnNodes = null;

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Transparent images not displaying correctly

If images are not displaying correctly or showing a black spot at the back side of the image then play with the color depth property of imagelist or picture box.

Example :-

ImageList imageList = new ImageList();
imagelist.colorDepth = colorDepth.32Bit;

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How to make Regular Expressions

If you want to learn how to make regular expressions then visit this link this will be helpful for you...

http://www.zytrax.com/tech/web/regex.htm

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Collection of Regular Expressions

Regular expression to match email address

1 :- [\w-]+@([\w-]+\.)+[\w-]+
2 :- (?(?![ ])(\w|[.])*@(\w|[.])*)
3 :- ^[\w\.=-]+@[\w\.-]+\.[\w]{2,3}$
4 :- /(^[a-z]([a-z_\.]*)@([a-z_\.]*)([.][a-z]{3})$)|(^[a-z]([a-z_\.]*)@
([a-z_\.]*)(\.[a-z]{3})(\.[a-z]{2})*$)/i

Regular Expression to validate US-Phone number.

Example :- (999) 999-9999 or (999)123-7869
1 :- /^\([1-9]\d{2}\)\s?\d{3}\-\d{4}$/


Regular Expression which validate string which contains only valid numbers.

1 :- /(^-?\d\d*\.\d*$)|(^-?\d\d*$)|(^-?\.\d\d*$)/


Regular Expression which validate string which contains only valid integer numbers.
1 :- /(^-?\d\d*$)/

Regular Expression to validate US-Zip Code
1:- /(^\d{5}$)|(^\d{5}-\d{4}$)/;

Regular Expression to check any social number :-
Replace 9 by any valid nuber you want to check
1 :-/^\d{9}$/

Expression to check amount example :- 100,100.00,$100,$100.00
1 :- /^((\$\d*)|(\$\d*\.\d{2})|(\d*)|(\d*\.\d{2}))$/

Regular Expression to check IP Address (0-255):-
/^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$/

Regular Expression to check Time :-

/^([1-9]|1[0-2]):[0-5]\d(:[0-5]\d(\.\d{1,3})?)?$/
Like :- HH:MM:SS, HH:MM, HH:MM:SS.mmm

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How to make Recycle - Bin in .net using C#

Visit this article and make your recycle bin

http://www.codeproject.com/KB/shell/recyclebin.aspx

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Detect the Encoding Type of given file

Encoding type : To add new Encoding we have to add new member in here,with the CodePage value as an value of the new encoding and have to modify FileHandler.DetectEncoding function.

public enum EncodingType
{
WindowsANSI = 1252,
Unicode = 1200,
UnixANSI = 28591
}

You can pass the path of the file and this method returns the encoding format
of type which has been defined in enum EncodingType.You just modify the enum with your encoding and code page value and get the encoding format of any file.

private Encoding DetectEncoding(string fileName)
{
byte[] data = new byte[4];
Encoding encoding = null;
StreamReader streamReader = new StreamReader(fileName);
streamReader.BaseStream.Read(data, 0, data.Length);

ApplicationNativeMethods.IsTextUnicodeFlags isTextUnicodeFlags = ApplicationNativeMethods.IsTextUnicodeFlags.UnicodeMask;
bool isTextUnicode = ApplicationNativeMethods.IsTextUnicode(data, 4, ref isTextUnicodeFlags);

if ((data[0] == 0xFF && data[1] == 0xFE) || (isTextUnicode == true))
{
encoding = Encoding.GetEncoding((int)EncodingType.Unicode);
}
else
{
streamReader.BaseStream.Position = 0;

char cr = char.MinValue;
char lf = char.MinValue;
char peekLf = char.MinValue;

while ((streamReader.EndOfStream != true))
{
peekLf = (char)streamReader.Peek();
if (peekLf == Constants.SYMBOL_LINEFEED)
{
cr = lf;
lf = (char)streamReader.Read();
break;
}
lf = (char)streamReader.Read();
}

if (cr != Constants.SYMBOL_CARRIAGERETURN)
{
encoding = Encoding.GetEncoding((int)EncodingType.UnixANSI);
}
else
{
encoding = Encoding.GetEncoding((int)EncodingType.WindowsANSI);
}
}
streamReader.Close();
return encoding;
}

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Sorted List Implementation

In C# You can implement Sortedlist and sort the values according to the key.

using System;
using System.Collections;

Code:

static void Main(string[] args)
{
values in sorted list are sorted according to key

SortedList myList = new SortedList();

myList.Add(12, "December");
myList.Add(9, "September");
myList.Add(10, "October");
myList.Add(4, "April");
myList.Add(5, "May");
myList.Add(6, "June");
myList.Add(2, "February");
myList.Add(8, "August");
myList.Add(7, "July");
myList.Add(3, "March");
myList.Add(11, "November");
myList.Add(1, "January");

output values that are sorted according to key


foreach (DictionaryEntry item in myList)
{
Console.WriteLine(item.Value);
}
}

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Hash Table Implementation

using System;
using System.Collections;

Code:

static void Main(string[] args)
{
Create an object of hash table
Hashtable myHash = new Hashtable();

Add key-pair values

myHash.Add("Saurabh", 1);
myHash.Add("Sandy", 2);
myHash.Add("Vivek", 3);

Move through hashtable data in cycle

foreach (DictionaryEntry item in myHash)
{
Console.WriteLine(item.Key);
Console.WriteLine(item.Value);
}

Get first item
Console.WriteLine("Get first item: " + myHash["Saurabh"]);

This will not work, name of item is not identical
Console.WriteLine("Get second item: " + myHash["Sandy"]);

}

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Get System Boot Configuration using C#

using System;
using System.Management;

Code:

static void Main(string[] args)
{
WqlObjectQuery query = new WqlObjectQuery("SELECT * FROM Win32_BootConfiguration");

ManagementObjectSearcher find = new ManagementObjectSearcher(query);

foreach (ManagementObject mo in find.Get())
{

Console.WriteLine("Boot directory with files required for booting.." + mo["BootDirectory"]);

Console.WriteLine("Description.." + mo["Description"]);

Console.WriteLine("Directory with temporary files for booting.." + mo["ScratchDirectory"]);

Console.WriteLine("Directory with temporary files.." + mo["TempDirectory"]);

}

}

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Get Environment variables..

Namespaces:

using System;
using System.Management;

Code:

static void Main(string[] args)
{
WqlObjectQuery query = new WqlObjectQuery("Select * from Win32_Environment");

ManagementObjectSearcher find = new ManagementObjectSearcher(query);

Console.WriteLine("Description - Name - User Name - Value");

foreach (ManagementObject mo in find.Get())
{

Console.WriteLine(mo["Description"] + " - " + mo["Name"] + " - " + mo["UserName"] + " - " + mo["VariableValue"]);
}
}

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Obtain IP address and host

Namespaces:

using System;
using System.Net;

Code:

static void Main(string[] args)
{
Get Host Name
string host = Dns.GetHostName();

Console.WriteLine("Hostname is: {0}", host);

GetIP Entry
IPHostEntry entry = Dns.GetHostByName(host);

foreach (IPAddress ip in entry.AddressList)
{
Console.WriteLine("IP address: " + ip.ToString());
}
}

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Send mail message to .net Environment (Enjoy Mail System)

Namespaces:

using System;
using System.Web.Mail;

Code:

static void Main(string[] args)
{
MailMessage mailMsg = new MailMessage();

mailMsg.From = "saurabhsingh_jnu06@yahoo.co.in";

mailMsg.To = "saurabhjnumca@gmail.com";

mailMsg.Cc = string.Empty;

mailMsg.Bcc = string.Empty;

mailMsg.Subject = "Here goes a subject";

mailMsg.Body = "Here goes email body";

mailMsg.Priority = (MailPriority)1;

mailMsg.Attachments.Add(new MailAttachment("d:\\myText.txt"));

SmtpMail.SmtpServer = "smarthost";

SmtpMail.Send(mailMsg);
}

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Network Operations in C# (Play with system)

Retrieve DNS computer name

public static void Main(string[] args)
{
Console.WriteLine(“DNS: {0}”, System.Net.Dns.GetHostByName“LocalHost”).HostName);
}

Retrieve NetBIOS computer name

public static void Main(string[] args)
{
Console.WriteLine(“NetBIOS: {0}”, System.Environment.MachineName);}

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To get the system Icons(handle of system imagelist)

[StructLayout(LayoutKind.Sequential)]
public struct SHFILEINFO
{
public IntPtr hIcon;
public IntPtr iIcon;
public uint dwAttributes;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 260)]
public string szDisplayName;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 80)]
public string szTypeName;
};

class Win32
{
public const uint SHGFI_ICON = 0x100;
public const uint SHGFI_LARGEICON = 0x0; // 'Large icon
public const uint SHGFI_SMALLICON = 0x1; // 'Small icon

[DllImport("shell32.dll")]
public static extern IntPtr SHGetFileInfo(string pszPath,
uint dwFileAttributes,
ref SHFILEINFO psfi,
uint cbSizeFileInfo,
uint uFlags); }

//the handle to the system image list
IntPtr hImgSmall;

//the handle to the system image list
//IntPtr hImgLarge;

//Create an object of
SHFILEINFO shinfo = new SHFILEINFO();

try
{
//Use this to get the small Icon
hImgSmall = Win32.SHGetFileInfo( Path of file, 0, ref shinfo,
(uint)Marshal.SizeOf(shinfo),
Win32.SHGFI_ICON |
Win32.SHGFI_SMALLICON
);
Icon myIcon =Icon.FromHandle(shinfo.hIcon);

//This return the index on=f system image list
int iconIndex = shinfo.iIcon;

//Add the icon to imagelist or where ever you want to use you can
imageList.Images.Add(myIcon);
}
catch (Exception)
{

}

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To close the application from task manager.

If you have closed your appplication but still it runs in task manager then you can use this method to kill the thread.It happens only when some thread of your application is not closed.

Code:-

public const int SC_CLOSE = 0xF060;
public const int WM_SYSCOMMAND = 0x0112;

//Override method when You will close the window
protected override void WndProc(ref System.Windows.Forms.Message m)
{
if (m.Msg == WM_SYSCOMMAND && (int)m.WParam == SC_CLOSE)

//close the application
MyClose();
// your method that cleans everything up and then runs
// System.Environment.Exit(0) which WILL close the threads forcefully if needed

base.WndProc(ref m);
}

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Play with Date-Time-Formats in C#

Code:

public static void Main(string[] args)
{
//Get the cureent date time
DateTime datetTime= DateTime.Now;

Formatting DateTime to full pattern (dddd, MMMM dd, yyyy hh:mm:ss)
Console.WriteLine(dt.ToString("F"));

Formatting DateTime to short date- time pattern (dddd, MMMM dd, yyyy, hh:mm)
Console.WriteLine(dt.ToString("f"));

Formatting DateTime to short date numerical pattern (M/d/yyyy)
Console.WriteLine(dt.ToString("d"));

Formatting DateTime to full date numeric pattern (dddd, MMMM dd, yyyy)
Console.WriteLine(dt.ToString("D"));

To the short date&time numerical pattern (M/d/yyyy hh:mm)
Console.WriteLine(dt.ToString("g"));

To the full date&time numerical pattern (M/d/yyyy hh:mm:ss)
Console.WriteLine(dt.ToString("G"));

DateTime to the month name pattern (MMMM dd)
Console.WriteLine(dt.ToString("m"));

DateTime to the short date pattern (MMMM, yyyy)
Console.WriteLine(dt.ToString("y"));

DateTime to the long time pattern (hh:mm:ss)
Console.WriteLine(dt.ToString("T"));

DateTime to the short time pattern (hh:mm)
Console.WriteLine(dt.ToString("t"));

DateTime to the RFC1123 pattern (ddd, dd MMM yyyy HH':'mm':'ss 'GMT')
Console.WriteLine(dt.ToString("r"));

DateTime to sortable pattern This format is based on ISO 8601 and uses local time.
Console.WriteLine(dt.ToString("s"));

DateTime to full date&time using universal time
Console.WriteLine(dt.ToString("U"));

DateTime to universal sortable pattern (yyyy'-'MM'-'dd HH':'mm':'ss'Z')
Console.WriteLine(dt.ToString("u"));
}

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How to get Memory Info

Namespaces:

using System;

using System.Management;

Code:

static void Main(string[] args)
{

WqlObjectQuery query = new WqlObjectQuery("SELECT * FROM Win32_PerfFormattedData_PerfOS_Memory");

ManagementObjectSearcher find = new ManagementObjectSearcher(query);

//Traverse each management object.
foreach (ManagementObject mo in find.Get())
{

Console.WriteLine("Available bytes: " + mo["AvailableBytes"]);

Console.WriteLine("Available KBs: " + mo["AvailableKBytes"]);

Console.WriteLine("Available MBs: " + mo["AvailableMBytes"]);

Console.WriteLine("Cache bytes: " + mo["CacheBytes"]);

Console.WriteLine("Cache bytes peak: " + mo["CacheBytesPeak"]);

Console.WriteLine("Cache bytes: " + mo["CacheBytes"]);

Console.WriteLine("Commit limit: " + mo["CommitLimit"]);

Console.WriteLine("Committed bytes: " + mo["CommittedBytes"]);

Console.WriteLine("Free system page table entries: " + mo["FreeSystemPageTableEntries"]);

Console.WriteLine("Pool paged bytes: " + mo["PoolPagedBytes"]);

Console.WriteLine("System code total bytes: " + mo["SystemCodeTotalBytes"]);

Console.WriteLine("System driver total bytes: " + mo["SystemDriverTotalBytes"]);

}

}

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Open Control Panel Items using Shell (COM)

Namespaces:

using System;
// this is COM component that can be found under the name "Microsoft Shell Controls And Automation"
// this must be added to project references

using Shell32;

Code:

static void Main()
{
//Creating an object of shell to access all the control panel items.
Shell shell = new Shell();

// accessibility options
shell.ControlPanelItem("access.cpl");

// add-remove programs
shell.ControlPanelItem("appwiz.cpl");

// bluetooth configuration
shell.ControlPanelItem("btcpl.cpl");

// desktop settings
shell.ControlPanelItem("desk.cpl");

// directX properties
shell.ControlPanelItem("directx.cpl");

// add hardware wizard
shell.ControlPanelItem("hdwwiz.cpl");

// internet properties
shell.ControlPanelItem("inetcpl.cpl");

// regional and language options
shell.ControlPanelItem("intl.cpl");

// Wireless link
shell.ControlPanelItem("irprops.cpl");

// Game controllers
shell.ControlPanelItem("joy.cpl");

// Mouse properties
shell.ControlPanelItem("main.cpl");

// Sounds and audio devices properties
shell.ControlPanelItem("mmsys.cpl");

// Network connections
shell.ControlPanelItem("ncpa.cpl");

// User accounts
shell.ControlPanelItem("nusrmgr.cpl");

// ODBC datasource administrator

shell.ControlPanelItem("odbccp32.cpl");

// Power options properties
shell.ControlPanelItem("powercfg.cpl");

// System properties
shell.ControlPanelItem("sysdm.cpl");

// Location information - telephone properties
shell.ControlPanelItem("telephon.cpl");

// Date and time properties
shell.ControlPanelItem("timedate.cpl");

// Automatic updates - WindowsUpdate settings

shell.ControlPanelItem("wuaucpl.cpl");
}

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Get folder items using Windows folder dialog

Namespaces:

using System;

using Shell32;

Code:

static void Main()
{

Shell shell = new Shell();

// open dialog for desktop folder

// use appropriate constant for folder type ShellSpecialFolderConstants

Folder folder = shell.BrowseForFolder(0, "folderPath/FilePath",0 ,ShellSpecialFolderConstants.ssfDESKTOP); if (folder != null)
{
foreach (FolderItem fi in folder.Items())
{
Console.WriteLine(fi.Name);
}

}

}

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