Microsoft Visual Basic 2010 Step by Step eBook

Chapter 13 Exploring Text Files and String Processing 327

processing the textual elements in your programs. In this section, you’ll learn about several

ways to process strings.

The most common task you’ve accomplished so far with strings in this book is concatenating

them by using the concatenation operator (&). For example, the following program

statement concatenates three literal string expressions and assigns the result “Bring on the

circus!” to the string variable Slogan:

Dim Slogan As String

Slogan = "Bring" & " on the " & "circus!"

You can also concatenate and manipulate strings by using methods in the String class of

the .NET Framework library. For example, the String.Concat method allows equivalent string

concatenation by using this syntax:

Dim Slogan As String

Slogan = String.Concat("Bring", " on the ", "circus!")

Visual Basic 2010 features two methods for string concatenation and many other

string-processing tasks: You can use operators and functions from earlier versions of

Visual Basic (Mid, UCase, LCase, and so on), or you can use newer methods from the .NET

Framework (Substring, ToUpper, ToLower, and so on). There’s no real penalty for using either

string-processing technique, although the older methods exist primarily for compatibility

purposes. (By supporting both methods, Microsoft hopes to welcome upgraders and their

existing code base, allowing them to learn new features at their own pace .) In the rest of this

chapter, I’ll focus on the newer string-processing functions from the .NET Framework String

class. However, you can use either string-processing method or a combination of both.

Table 13-2 lists several methods and one property in the String class that appear in

subsequent exercises and their close equivalents in the Visual Basic programming language.

The fourth column in the table provides sample code using the String class.

TABLE 13-2 Elements of the String Class and Visual Basic Equivalents

String

Method or

Property

Visual

Basic

Function Description String Example

ToUpper UCase Changes letters in a string

to uppercase.

Dim Name, NewName As String

Name = "Kim"

NewName = Name.ToUpper

'NewName = "KIM"

ToLower LCase Changes letters in a string

to lowercase.

Dim Name, NewName As String

Name = "Kim"

NewName = Name.ToLower

'NewName = "kim"

Length Len Determines the number

of characters in a string.

Dim River As String

Dim Size As Short

River = "Mississippi"

Size = River.Length

'Size = 11