C# Tip and Traps 2

1. Changing Thread Culture

    
       [TestMethod]
        public void Example()
        {
            const string turkeyCultureString = "tr-TR";
            const string australiaCultureString = "en-AU";
            const double someNumber = 23.45;


            Debug.WriteLine("Setting English language - Australia country/region" );  

            var australiaCultureInfo = CultureInfo.GetCultureInfo(australiaCultureString);
            Thread.CurrentThread.CurrentCulture = australiaCultureInfo;

            var ausUppercaseI = "i".ToUpper();
       
            Debug.WriteLine(ausUppercaseI);
            Debug.WriteLine(someNumber);
            Debug.WriteLine(DateTime.Now);




            Debug.WriteLine("Setting Turkish language - Turkey country/region");

            var turkeyCultureInfo = CultureInfo.GetCultureInfo(turkeyCultureString);
            Thread.CurrentThread.CurrentCulture = turkeyCultureInfo;

            var turUppercaseI = "i".ToUpper();            

            Debug.WriteLine(turUppercaseI);
            Debug.WriteLine(someNumber);
            Debug.WriteLine(DateTime.Now);
        }

 

결과

 

2.  Random Number Generating for Cryptography

   
        [TestMethod]
        public void HighSecurity()
        {
            var r = System.Security.Cryptography.RandomNumberGenerator.Create();

            var randomBytes = new byte[4]; // 4 bytes so we can convert to an 32-bit int

            r.GetBytes(randomBytes);

            int rndInt = BitConverter.ToInt32(randomBytes, 0);

            Debug.WriteLine(rndInt);          
        }

 

3. Careful for using Hashcode

특정 클래스의 객체의 hashcode를 사용할 때에는 해당 값을 사용중에 임의로 변경이 가능하도록 만들면, 아래의 코드에서는 문제가 발생할 수 있다.

 

<잘못된 구현>

 

        public void BadGetHashCodeExample()
        {
            var p1 = new PersonIdBadHash {Id = 1};
            var p2 = new PersonIdBadHash {Id = 2};

            var d = new Dictionary();

            d.Add(p1, "Sarah");
            d.Add(p2, "John");

            var john = d[p2];

            p2.Id = 99;

            john = d[p2];       // error 발생
        }

 

Id 의 값을 변경함에 따라 key 값이 변경되어 element를 찾을 수 없어 오류가 발생함.

 

<좋은 예>

 

정의

     internal class PersonIdBetterHash
    {
        public PersonIdBetterHash(int id)
        {
            Id = id;
        }

        public int Id { get; private set; }

        public override int GetHashCode()
        {
            return Id.GetHashCode();
        }

        // Equals override omitted
    }

 

 

구현    
       

    public void BetterGetHashCodeExample()
     {
         var p1 = new PersonIdBetterHash(1);
         var p2 = new PersonIdBetterHash(2);

         var d = new Dictionary();
         d.Add(p1, "Sarah");
         d.Add(p2, "John");
         var john = d[p2];
         // p2.Id = 99; Id is now immutable, so our hashcode cannot change now
     }

 

 

 

 

 

4. Combinable Enum using Flag Attribute

 

// Example of the FlagsAttribute attribute.
using System;

class FlagsAttributeDemo
{
    // Define an Enum without FlagsAttribute.
    enum SingleHue : short
    {
        Black = 0,
        Red = 1,
        Green = 2,
        Blue = 4
    };

    // Define an Enum with FlagsAttribute.
    [FlagsAttribute] 
    enum MultiHue : short
    {
        Black = 0,
        Red = 1,
        Green = 2,
        Blue = 4
    };

    static void Main( )
    {
        Console.WriteLine( 
            "This example of the FlagsAttribute attribute \n" +
            "generates the following output." );
        Console.WriteLine( 
            "\nAll possible combinations of values of an \n" +
            "Enum without FlagsAttribute:\n" );

        // Display all possible combinations of values.
        for( int val = 0; val <= 8; val++ )
            Console.WriteLine( "{0,3} - {1}", 
                val, ( (SingleHue)val ).ToString( ) );

        Console.WriteLine( 
            "\nAll possible combinations of values of an \n" +
            "Enum with FlagsAttribute:\n" );

        // Display all possible combinations of values.
        // Also display an invalid value.
        for( int val = 0; val <= 8; val++ )
            Console.WriteLine( "{0,3} - {1}", 
                val, ( (MultiHue)val ).ToString( ) );
    } 
} 

 

/*
This example of the FlagsAttribute attribute
generates the following output.

All possible combinations of values of an
Enum without FlagsAttribute:

  0 - Black
  1 - Red
  2 - Green
  3 - 3
  4 - Blue
  5 - 5
  6 - 6
  7 - 7
  8 - 8

All possible combinations of values of an
Enum with FlagsAttribute:

  0 - Black
  1 - Red
  2 - Green
  3 - Red, Green
  4 - Blue
  5 - Red, Blue
  6 - Green, Blue
  7 - Red, Green, Blue
  8 - 8
*/