Variables

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I've been using variables throughout the first two chapters, and you may have a loose idea of what a variable is and does. Remember a variable is nothing more than a container.

If you come from a traditional ASP background, variables created sloppy coding behavior because variables weren't really variables in the truest sense of the word. They were variants and could basically hold anything without ever indicating what type of data the variable was holding. Now variables must be told what they are holding, otherwise…BOOM!!! It won't work.

We are going to explore variables and their data types in both languages. There are some differences in names, the way you address variables, and how you manipulate them. First I must show you what data types are available and what their names are.

Data Types

The language-specific data type names in the following table aren't really the data types themselves. They are pointers. Do you know what they point to? You guessed it objects! These objects handle the data types and their properties and methods. These can also be explored in the .NET Framework Class Library explorer mentioned at the end of Chapter 2.

Table 3.1 shows the pointer names for both languages, their corresponding .NET object, and an explanation of what that data type can hold.

Table 3.1. Data Types

Visual Basic .NET Type	C# Type	.NET Framework Type	Range
Boolean	bool	System.Boolean	True or False
Byte	byte	System.Byte	0-255
Char	char	System.Char	0-65535 Unicode Character
Date	DateTime	System.Datetime	January 1, 0001 to December 31, 9999
Decimal	decimal	System.Decimal	Approx. 1.0_10-28 to 7.9_1028
Double	double	System.Double	Approx. ±5.0_10-324 to ±1.7_10308
Integer	int	System.Int32	-2,147,483,648 to 2,147,483,647
Long	long	System.Int64	-9,223,372,036, 854,775,808 to 9,223,372,036, 854,775,807
N/S	sbyte	System.SByte	-128 to 127
Short	short	System.Int16	-32,768 to 32,767
Single	float	System.Single	Approx. ±1.5_10-45 to ±3.4_1038
String	string	System.String	0 to approximately 2 billion Unicode characters
N/S	ushort	System.UInt16	0 to 65,535
N/S	uint	System.UInt32	0 to 4,294,967,295
N/S	ulong	System.UInt64	0 to 18,446,744,073, 709,551,615
N/S = Not Supported

Don't be intimidated by all the different data types and numbers. I really only put this in the book to impress you with my knowledge of the vast and seemingly infinite range of data one can manipulate with these data types and their corresponding objects.

YEAH…RIGHT!!!

Seriously, this is best way I can explain data types to you: The raisin between my ears has boiled it down to the descriptions in the sections that follow.

Boolean

Boolean, which is shown in Table 3.2, is about as simple a data type as there can be. True or false. That's it.

Table 3.2. Boolean

Visual Basic .NET Type	C# Type	.NET Framework Type	Range
Boolean	bool	System.Boolean	True or False

Numbers

There are numbers with decimals, numbers without decimals that can have negative numbers, and numbers without decimals that start at 0 and go up. (The latter are available only in C#.) Big, Bigger, and Super Size, for all three as seen in Table 3.3 and Table 3.4.

Table 3.3. Numbers without Decimals

Visual Basic .NET Type	C# Type	.NET Framework Type	Range
Byte	byte	System.Byte	0-255
N/S	sbyte	System.SByte	-128 to 127
Short	short	System.Int16	Big number, no decimal, can start below 0
Integer	int	System.Int32	Bigger number, no decimal, can start below 0
Long	long	System.Int64	Super Size number, no decimal, can start below 0
N/S	ushort	System.UInt16	Big number, no decimal, that starts at 0
N/S	uint	System.UInt32	Bigger number, no decimal, that starts at 0
N/S	ulong	System.UInt64	Super Size number, no decimal, that starts at 0

Table 3.4. Numbers with Decimals

Visual Basic .NET Type	C# Type	.NET Framework Type	Range
Single	float	System.Single	Big number with decimal
Double	double	System.Double	Bigger number with decimal
Decimal	decimal	System.Decimal	Super Size number with decimal

To give you an idea how big a Super Size number is, its largest possible value is

 +/-79,228,162,514,264,337,593,543,950,335 

That's like 9 trillion or zillion or something like that. Like I said…SUPER SIZED!!!

Note

The size differences of the variables in the Table 3.3 and 3.4 bring up an issue that I'd like to address. The larger the variable you use, the more server memory you use, so it is good practice to use variables that are sufficient enough in capability to contain what you will be placing in them but to not use anything larger. Using larger variables puts undue requirements on the server and allocates memory that you will never use. That said, I can tell you that in all my years of programming I've NEVER needed to use a Long or Super Size integer before.

Characters

This data type includes any type of character such as letters, numbers, and special characters. There are only two kinds of character data types. One is very small and the other is very large, as shown in Table 3.5.

Table 3.5. Characters

Visual Basic .NET Type	C# Type	.NET Framework Type	Range
Char	char	System.Char	Any single one of the 65535 Unicode characters
String	string	System.String	0 to approximately 2 billion Unicode characters

If you need to use more than one character, you've go no choice but to use a string not a difficult choice to make.

Dates and Times

This data type is pretty self-explanatory. It's used to store dates and times, as shown in Table 3.6.

Table 3.6. Date & Time

Visual Basic .NET Type	C# Type	.NET Framework Type	Range
Date	DateTime	System.Datetime	January 1, 0001 to December 31, 9999

Declaring and Initializing Variables

In the previous chapters, you've seen a bit of variable declaration and initialization, but let's make it official and discuss some different techniques and shortcuts.

Remember, we declare variables like this:

Visual Basic .NET

dim var1 as integer 

C#

int var1; 

And variables are initialized like this:

Visual Basic .NET

var1 = 1 

C#

var1 = 1; 

It's also possible to declare multiple variables of the same type at the same time. They simply need to be separated by commas:

Visual Basic .NET

dim var1,var2,var3 as integer 

C#

int var1,var2,var3; 

You can declare and initialize variables on the same line, as well, for a shortcut of sorts.

Visual Basic .NET

dim var1 as integer = 1 

C#

int var1 = 1; 

Now here's a place where C# has some advantage over Visual Basic .NET. C# allows you to declare and initialize multiple variables of the same type on the same line.

C#

int var1 = 1, var2 = 2, var3 = 3; 

You cannot use this type of technique in Visual Basic .NET.

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