Console.OutputEncoding

Sometimes we need to output non-english characters in Console, this is possible(really?) using Console.OutputEncoding property. Below is sample code to output latin & chinese characters

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;

namespace Test
{
    class Program
    {
        static string latinString = "蘇雷什";
        static string chineseString = "蘇雷什:密碼";

        [DllImport("kernel32.dll")]
        static extern bool SetConsoleOutputCP(uint wCodePageID);

        static void Main(string[] args)
        {
            var latinEncoding = Encoding.GetEncoding("ISO-8859-1");
            var utf8Encoding = Encoding.GetEncoding("UTF-8");

            //-------Start Chinese Characters------------

            SetConsoleOutputCP((uint)utf8Encoding.CodePage);

            Console.OutputEncoding = utf8Encoding;
            Console.WriteLine(chineseString);
          
            //-------End Chinese Characters------------

            //-------Start Latin Characters------------

            SetConsoleOutputCP((uint)latinEncoding.WindowsCodePage);

            Console.OutputEncoding = latinEncoding;
            Console.WriteLine(latinString);

            //-------End Latin Characters------------
        }
    }
}

But wait - it ain't going to display on windows(English) OS.

http://stackoverflow.com/questions/6405428/can-i-get-console-to-show-chinese
http://social.msdn.microsoft.com/Forums/en-US/csharpgeneral/thread/fe549b29-3e09-4176-b317-1e0094abf71a/
http://www.csharp-examples.net/culture-names/
http://stackoverflow.com/questions/2213541/vietnamese-character-in-net-console-application-utf-8

EAS References

Just for my reference

http://msdn.microsoft.com/en-us/library/hh361570%28v=exchg.140%29.aspx
http://msdn.microsoft.com/en-us/library/hh531590%28v=exchg.140%29.aspx

Useful functions - contd.....

public static void PrintHexString(byte data)
{
     Console.WriteLine("Hex of {0} is {1}", data, BitConverter.ToString(BitConverter.GetBytes(data)));
}
-----------------------
private static void DemoNegativeNumberStorageInBinary()
{
            Console.WriteLine("Binary Representation of {0} - {1}", 1000, Convert.ToString(1000, 2));

            /* how negative is done
             * short value = -7;
             * 7 = 0000 0000 0000 0111
             * Not (7) = 1111 1111 1111 1000
             * Add 1 = 1111 1111 1111 1000
             *                           +
             *                           1
             *         1111 1111 1111 1001
             *         (1)111 1111 1111 1001 - is negative because it is 1
             *        
             *         -7 + 7 = 0
             *          1111 1111 1111 1001 (+)
             *          0000 0000 0000 0111
             *          0000 0000 0000 0000
            */
            Console.WriteLine("Binary Representation of {0} - {1}", -1000, Convert.ToString(-1000, 2));
}
-----------------------

Unicode and Encoding

Just for my reference
http://csharpindepth.com/Articles/General/Unicode.aspx
http://stackoverflow.com/questions/496321/utf8-utf16-and-utf32
http://stackoverflow.com/questions/643694/utf-8-vs-unicode

In nutshell
1. .Net, by default use UTF - 16, and Encoding.Unicode means  UTF - 16.
2.  UTF8: Variable-width encoding, backwards compatible with ASCII. ASCII characters (U+0000 to U+007F) take 1 byte, code points U+0080 to U+07FF take 2 bytes, code points U+0800 to U+FFFF take 3 bytes, code points U+10000 to U+10FFFF take 4 bytes. Good for English text, not so good for Asian text.
3. UTF16: Variable-width encoding. Code points U+0000 to U+FFFF take 2 bytes, code points U+10000 to U+10FFFF take 4 bytes. Bad for English text, good for Asian text.
4. UTF32: Fixed-width encoding. All code points take 4 bytes. An enormous memory hog, but fast to operate on. Rarely used.

SQL Server DateTime vs .Net DateTime

Just for reference
http://seesharper.wordpress.com/2008/07/08/sql-server-datetime-vs-net-datetime-battle-of-accuracy/
http://stackoverflow.com/questions/1021755/compare-two-datetime-values-from-sql-server-with-c-sharp/1021838#1021838
http://codebetter.com/petervanooijen/2008/08/21/valid-date-time-values-in-sql-server-sqldatetime-vs-datetime/

Abstract Factory vs Factory

There are numerous post out there to explain the differences - i just wanted to add on

Factory - encapsulates the logic of creating a concrete type
Abstract Factory - encapsulates grouping of related factories.

I always start with Factory pattern first to decouple the creation logic from client.
So when will we go for Abstract Factory - as soon as your factory method violates Open/Closed principle. If your Factory method contains lots of 'if/else' or 'switch' statements, then it is time to move onto Abstract Factory. Please refer this article.

Also DBProviderFactory is another example of AF pattern. SqlClientFactory, OracleClientFactory, OleDbFactory are all grouped under DBProviderFactory.

http://en.wikipedia.org/wiki/Abstract_factory_pattern
http://en.wikipedia.org/wiki/Factory_object
http://msdn.microsoft.com/en-us/library/dd0w4a2z%28v=vs.80%29.aspx

Modifying Web.Config at run time

Sample code to update an app setting in web.config file at run time. I assume the user have physical path of the web.config, instead of virtual directory.

private static void ChangeAppSettting(string oldValue, string newValue)
{
            string appSettingName = "your app setting name";
            string configFilePath = "Your web.config path";
            Configuration configuration = OpenConfigFile(configFilePath );

            AppSettingsSection appSettings = configuration.AppSettings;

            if (appSettings != null && appSettings.Settings[appSettingName] != null)
            {
                appSettings.Settings[AppSetting].Value = newValue;
                configuration.Save();
            }
        }

        private static Configuration OpenConfigFile(string configPath)
        {
            FileInfo configFile = new FileInfo(configPath);
            VirtualDirectoryMapping virtualDirectoryMapping = new VirtualDirectoryMapping(configFile.DirectoryName, true, configFile.Name);
            var webConfigFileMap = new WebConfigurationFileMap();
            webConfigFileMap.VirtualDirectories.Add("/", virtualDirectoryMapping);
            return WebConfigurationManager.OpenMappedWebConfiguration(webConfigFileMap, "/");
        }