Class StringBuilder

Table of contents:

The string class provides many capabilities for processing strings. However a string's contents can never change. Operations that seem to concatenate strings are in fact assigning string references to newly created strings (e.g., the += operator creates a new string and assigns the initial string reference to the newly created string).

The next several sections discuss the features of class StringBuilder (namespace System.Text), used to create and manipulate dynamic string informationi.e., mutable strings. Every StringBuilder can store a certain number of characters that is specified by its capacity. Exceeding the capacity of a StringBuilder causes the capacity to expand to accommodate the additional characters. As we will see, members of class StringBuilder, such as methods Append and AppendFormat, can be used for concatenation like the operators + and += for class string.

Performance Tip 16 2

Objects of class string are immutable (i.e., constant strings), whereas object of class StringBuilder are mutable. C# can perform certain optimizations involving strings (such as the sharing of one string among multiple references), because it knows these objects will not change.

Class StringBuilder provides six overloaded constructors. Class StringBuilderConstructor (Fig. 16.9) demonstrates three of these overloaded constructors.

Figure 16.9. StringBuilder class constructors.

 1 // Fig. 16.9: StringBuilderConstructor.cs
 2 // Demonstrating StringBuilder class constructors.
 3 using System;
 4 using System.Text;
 6 class StringBuilderConstructor
 8 public static void Main()
 9 {
10 StringBuilder buffer1, buffer2, buffer3;
12 buffer1 = new StringBuilder();
13 buffer2 = new StringBuilder( 10 );
14 buffer3 = new StringBuilder( "hello" );
16 Console.WriteLine( "buffer1 = "" + buffer1 + """ );
17 Console.WriteLine( "buffer2 = "" + buffer2 + """ );
18 Console.WriteLine( "buffer3 = "" + buffer3 + """ );
19 } // end method Main
20 } // end class StringBuilderConstructor
buffer1 = ""
buffer2 = ""
buffer3 = "hello"

Line 12 employs the no-parameter StringBuilder constructor to create a StringBuilder that contains no characters and has a default initial capacity of 16 characters. Line 13 uses the StringBuilder constructor that takes an int argument to create a StringBuilder that contains no characters and has the initial capacity specified in the int argument (i.e., 10). Line 14 uses the StringBuilder constructor that takes a string argument to create a StringBuilder containing the characters of the string argument. The initial capacity is the smallest power of two greater than or equal to the number of characters in the argument string, with a minimum of 16. Lines 1618 implicitly use StringBuilder method ToString to obtain string representations of the StringBuilders' contents.



    Introduction to Computers, the Internet and Visual C#

    Introduction to the Visual C# 2005 Express Edition IDE

    Introduction to C# Applications

    Introduction to Classes and Objects

    Control Statements: Part 1

    Control Statements: Part 2

    Methods: A Deeper Look


    Classes and Objects: A Deeper Look

    Object-Oriented Programming: Inheritance

    Polymorphism, Interfaces & Operator Overloading

    Exception Handling

    Graphical User Interface Concepts: Part 1

    Graphical User Interface Concepts: Part 2


    Strings, Characters and Regular Expressions

    Graphics and Multimedia

    Files and Streams

    Extensible Markup Language (XML)

    Database, SQL and ADO.NET

    ASP.NET 2.0, Web Forms and Web Controls

    Web Services

    Networking: Streams-Based Sockets and Datagrams

    Searching and Sorting

    Data Structures



    Appendix A. Operator Precedence Chart

    Appendix B. Number Systems

    Appendix C. Using the Visual Studio 2005 Debugger

    Appendix D. ASCII Character Set

    Appendix E. Unicode®

    Appendix F. Introduction to XHTML: Part 1

    Appendix G. Introduction to XHTML: Part 2

    Appendix H. HTML/XHTML Special Characters

    Appendix I. HTML/XHTML Colors

    Appendix J. ATM Case Study Code

    Appendix K. UML 2: Additional Diagram Types

    Appendix L. Simple Types


    Visual C# How to Program
    Visual C# 2005 How to Program (2nd Edition)
    ISBN: 0131525239
    EAN: 2147483647
    Year: 2004
    Pages: 600

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