Beginning ASP.NET 4.5 in CSharp and VB Opsylum

Data Types and Variables x 151
SelectedValue of a DropDownList. To get a string representation of an Object, you can call its
ToString() method. Every object in the .NET world supports this method, although the exact
behavior may differ from object to object. For now, it’s important to understand that ToString is a
method — or an operation — on an object, like a String or a Double and even the parent Object
itself. You learn more about methods and objects later in this chapter when object-oriented programming
is discussed.
Using ToString() is easy, as the following example that outputs today’s date and time on a Label
control demonstrates:
VB.NET
Label1.Text = System.DateTime.Now.ToString()
C#
Label1.Text = System.DateTime.Now.ToString();
Another way to convert data types is by using the Convert class.
NOTE Classes are an important concept in .NET, so they are discussed in their
own section later in this chapter. For now it’s important to understand that a
class is like a blueprint for objects that are used in .NET. You can create your
own classes, but you will also use many of the standard classes that are part of
the .NET Framework.
The Convert class contains functionality to convert a number of data types into another type. The
following is a simple example of converting a String containing a value that looks like a boolean
into a true Boolean type:
VB.NET
Dim myBoolean1 As Boolean = Convert.ToBoolean("True") ' Results in True
Dim myBoolean2 As Boolean = Convert.ToBoolean("False") ' Results in False
C#
bool myBoolean1 = Convert.ToBoolean("True");
bool myBoolean2 = Convert.ToBoolean("False");
// Results in true
// Results in false
Besides the ToBoolean method, Convert offers you a host of other conversion methods, including
ToInt32 (for integer types), ToDateTime (for dates), and ToString.
Another way to convert one type into another is by using casting. With casting you actually force
one type into another, which is different from converting, in which the underlying value of a data
type is transformed into a new value.
Casting only works for compatible types. You can’t, for example, cast a DateTime into an Integer.
You can, however, cast similar types, like a Double to an Integer or a String to an Object.
The reverse of the latter example isn’t always true. Earlier I said that every data type in the .NET
Framework is based on the Object data type, meaning that, for example, a String is an Object.