C# 0 The Complete Reference

StringWriter

 called 

strwtr

 and outputs to it using 

WriteLine( )

.

Next, it creates a 

StringReader

 using the string contained in 

strwtr

. This string is obtained 

by calling 

ToString( )

 on 

strwtr

. Finally, the contents of this string are read using 

ReadLine( )

.

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T h e   C #   L a n g u a g e

Converting Numeric Strings to Their Internal Representation

Before leaving the topic of I/O, we will examine a technique useful when reading numeric 

strings. As you know, 

WriteLine( )

 provides a convenient way to output various types of 

data to the console, including numeric values of the built-in types, such as 

int

 and 

double

.

Thus,

WriteLine( )

 automatically converts numeric values into their human-readable form. 

However, a parallel input method that reads and converts strings containing numeric 

values into their internal, binary format is not provided. For example, there is no version of 

Read( )

 that reads from the keyboard a string such as “100” and then automatically converts 

it into its corresponding binary value that can be stored in an 

int

 variable. Instead, there are 

other ways to accomplish this task. Perhaps the easiest is to use a method that is defined for 

all of the built-in numeric types: 

Parse( )

.

Before we begin, it is necessary to state an important fact: All of C#’s built-in types, such 

as

int

 and 

double

, are actually just 

aliases

 (that is, other names) for structures defined by the 

.NET framework. In fact, the C# type and .NET structure type are indistinguishable. One is 

just another name for the other. Because C#’s value types are supported by structures, the 

value types have members defined for them.

For the numeric types, the .NET structure names and their C# keyword equivalents are 

shown here:

.NET Structure Name

C# Name

Decimal

decimal

Double

double

Single

float

Int16

shor t

Int32

int

Int64

long

UInt16

ushor t

UInt32

uint

UInt64

ulong

Byte

byte

SByte

sbyte

These structures are defined inside the 

System

 namespace. Thus, the fully qualified 

name for 

Int32

 is 

System.Int32

. These structures offer a wide array of methods that help 

fully integrate the value types into C#’s object hierarchy. As a side benefit, the numeric 

structures also define a static method called 

Parse( )

 that converts a numeric string into 

its corresponding binary equivalent.

There are several overloaded forms of 

Parse( )

. The simplest version for each numeric 

structure is shown here. It performs the conversion using the default locale and numeric 

style. (Other versions let you perform locale-specific conversions and specify the numeric 

style.) Notice that each method returns a binary value that corresponds to the string.

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