Beginning ASP.NET 4.5 in CSharp and VB Opsylum

Data Types and Variables x 147
NOTE The .NET Framework used by ASP.NET is huge and contains thousands
of types with hundreds of thousands of members. Clearly, you cannot memorize
all the types in the framework, so you need to make good use of resources like
IntelliSense and the online help. Navigating the MSDN site (http://msdn
.microsoft.com/en-us/library/) can sometimes be a daunting task. However,
I often find that searching for something like typeName type .NET MSDN brings up
exactly what I need. So, if I wanted to learn more about the string class, I’d type
string class .NET MSDN in my favorite search engine. Nine out of ten times the
first result is a link to the relevant page on the MSDN website, where I can learn
more about the class — where it’s defined and located and how to use it.
DATA TYPES AND VARIABLES
At first when you think about data that is used in some programming environment, you may not
realize that each piece of data has a data type. You may think that a computer would store the text
Hello World in exactly the same way as today’s date or the number 26; as a series of characters, for
example. However, to be able to effectively work with data, many programming languages have different
data types, and each data type is constrained to a specific type of information. Out of the box,
the .NET Framework comes with a long list of data types that enable you to work with numbers
(such as Int32, Int16, and Double), text strings (Char and String), dates (DateTime), true/false
constructs (the Boolean), and more. A list of the most common types is supplied later in this section.
For each major type of data there is a special data type. To work with that data, you can store it
in a variable that you need to declare first using the required data type. In VB.NET you use Dim
myVariable As DataType, whereas in C# you use DataType myVariable to declare a variable. A
valid variable name typically consists of letters, numbers, and underscores, and cannot start with a
number. These rules apply to other identifiers as well, such as classes and methods, which you see
later. The following example shows you how to declare two variables: an Integer (int in C#) to
hold a number and a String (string in C#) to hold a piece of text:
VB.NET
' Declare a variable of type Integer to hold medium sized whole numbers.
Dim distanceInMiles As Integer
' Declare a variable to hold some text like a first name.
Dim firstName As String
C#
// Declare a variable of type int to hold medium sized whole numbers.
int distanceInMiles;
// Declare a variable to hold some text like a first name.
string firstName;
These two code examples also contain comments, prefixed with a tick (') in VB.NET or two forward
slashes (//) in C#. You learn more about commenting your code later in this chapter.