psychoric still trying to figure out what this blog is about

Better comparison with enumeration

Suppose you have an enum list and a variable which value comes from external source. What do you usually do to compare against the enum list?

If (MyValue == "3") { //3 means ok, do some stuff }

What if one day you decide that you don't like 3 (for whatever reason) and change it to 30? You will have to find and replace the repeated value all over your project. Yes, you have the FindAndReplace function with most IDE, but holy cow, you only realize that the last couple of 3 meant something else!

So a safer way is to cast the value into appropriate enum for comparison or any other operation.

'VB.NET
dim myEnumValue as TheEnum = CType([Enum].Parse(GetType(TheEnum), _
				tempValue.ToString()), TheEnum)
If myEnumValue = TheEnum.NumberThree Then
	'..
End If

//C#
TheEnum myEnumValue = (TheEnum)Enum.Parse(typeof(TheEnum), tempValue);
if (myEnumValue == TheEnum.NumberThree) { //.. }

"Hey, that looks useful. I want it in my SuperCoolReusable library" you might say. With the power of Generic, we can put it into a common call.

'VB.NET
Public Shared Function ParseEnum(Of T)(ByVal Value As Object) As T
	Return CType([Enum].Parse(GetType(T), Value.ToString()), T)
End Function

//C#
public static ReturnType ConvertStringToEnum<ReturnType>(string Value)
{
	return (ReturnType)Enum.Parse(typeof(ReturnType), Value);
}

Another simple yet useful tip!

I Learned and Applied RegularExpression Today

Scenario: I have a number of patterns that I need to check and replace in a string. I don't want to transverse the string and play with characters and length. What other option I have?

I want the library FAST!

My MSDN 2008 Library didn't install a direct link to launch help like the 2005 version. So i tweaked the 2005 shortcut and hoila, i have the shortcut for 2008 version. You like the F1, but i prefer this so i can easily answer people's query without opening the IDE

Create a new Shortcut and put this in the shortcut path (single line):

"%YOUR PROGRAM FILES%\Common Files\Microsoft Shared\Help 9\dexplore.exe"
/helpcol ms-help://MS.MSDNQTR.v90.en /LaunchNamedUrlTopic DefaultPage

coalescing null yield return

Ok the title means nothing at all, and they are not related too, except that they both are of C# family. As requested by Klaw, i am going to blog about it so that we all learn

Coalescing Null Operator

You are probably thinking what's that. Maybe it is just me, but it is one of the cool subtle features in C# that I just discovered today. Shame on me ya. Basically you all are familiar with this:

string myStrVarB = (myStrVarA == null) ? "null string" : myStrVarA

So with coalescing null operator (??), you can shortened it to:

string myStrVarB = myStrVarA ?? "null string"

Let's see, that is saving of 17 characters. Your boss sure will praise you for that On a side note, in case you don't know, you can allow a scalar type to be null by using the nullable operator:

int? myInteger = null

yield return

Definition from MSDN: "Used in an iterator block to provide a value to the enumerator object or to signal the end of iteration". I assume you have previous knowledge with IEnumerable (or iterator), so i am not going into detail with it. The yield statement appears only inside an iterator block and returns the value that is expected by the calling foreach statement. Cut the theory and show me the example.

public static IEnumerable Power(int number, int exponent)
{
	int counter = 0;
	int result = 1;
	while (counter++ < exponent)
	{
		result = result * number;
		yield return result;
	}
}

static void Main()
{
	// Display powers of 2 up to the exponent 8:
	foreach (int i in Power(2, 8))
	{
		Console.Write("{0} ", i);
	}
}

There you go, another simple bit of my learning

Begin Invoke..End Invoke

First post in the category This group is mainly to share coding stuff that is out of layman term. If you are not programmer, stay away at all cost!

Found this very easy to read yet informative post on Asynchronous Method Invocation. I admit that what i know about .NET is merely the tiny tip of what the iceberg can offer. Oh hell, life is long and learning is life long, ain't it?

Here's a summary of what i learnt:

• MethodInvoke - built in delegate in .NET that allow you to call a method that takes in no parameter
• BeginInvoke - execute the target function and return to caller instantly
• ThreadPool in .NET has a limit of 25. Avoid 'starving' the pool else be fined by performance loss
• EndInvoke - return proper values/parameters from the previous function call
• IAsyncResult - log of all datas (exceptions, return value, output parameters, etc) after execution is completed
• AsyncCallBack - used when you don't wish to wait for completion of the execution (that's the purpose of asynchronous call bah)
• Command Pattern (ICommand interface) - rather than BeginInvoke, EndInvoke, CallBack everywhere in your Main(), apply this pattern to group calls together.

That's all folks. I might not have explained everything properly, so best for you to read it yourself.

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