In C# the Convert class binds all the basic data types together. It is possible to convert (cast) to and from most data types by using this class. Be careful that you are likely to lose information if you are casting to a type that hold less information.

Example 1: How to convert a C# string to an integer

string myString = “1024″;
int myInteger = Convert.ToInt32(myString);

Example 2: How to convert a C# integer to a string

int myInteger = 1024;
string myString = Convert.ToString(myInteger);

Example 3: How to convert a C# float/double to a string

It is possible to directly convert a float to a string, but not the other way around. Note that floating point type values in C# are automatically a double unless you force the compiler (f) to turn them into a float.

float myFloat = 1000.245f; // We need an “f”
string myString1 = Convert.ToString(myFloat);

double myDouble = 1000.245; // No need for an “f”
string myString2 = Convert.ToString(myDouble);

Example 4: How to convert a C# string to a float/double

If you would like to convert a string to a float you will need to convert it to a double first, and then cast it down. A float contains only 32 bits of information, and is thus less precise than a double (which holds 64 bits).

string myString = “1000.245″;
double myDouble = Convert.ToDouble(myString); // This is not a problem
float myFloat = (float) Convert.ToDouble(myString); // But we need to cast a float

This is a post from Martijn's C# Coding Blog.

When working with io streams (such when sending and receiving information from a NetworkStream) you often have to convert C# strings into Byte[] (byte arrays) and back again. At this point it is important to consider how you would like to encode your string. This post shows how you can pass a string to a method that only accepts byte arrays — and how you can turn byte arrays back into strings again.

One major difference between C and C# is the fact that all strings are stored as Unicode.

In the old days when computers were still newish ASCII devised a standard for the first 128 characters, so a byte (which can hold up to 256 characters) was sufficient for communication. As time went by, and computers had to speak more languages the second half (128-255) was mapped to various languages. Many different encoding schemes (also called code pages) were designed, including ones that could hold Japanese & Chinese (some 6000+ characters) while still fitting this information into just 256 available bytes.

It was however still impossible to write a single e-mail that contained Ancient Greek, Chinese and modern Russian. So work was started on the Unicode project. For Unicode it was decided that a 2 byte combination (65,536 values) was sufficient to hold all the worlds languages.

The basic unit of a memory cell, or a communication stream is still the byte. A function which sends or receives information thus has to work with Byte[] (byte arrays).

Solution #1 – Convert Unicode to ASCII / String to an ASCII Byte[]

If you intend to send only the most basic of messages which can be satisfied with just A-Z, a-z & 0-9 and a few other characters you can convert the C# string using the ASCII encoder. You will however lose any characters that are not defined by ASCII. So while this is a good idea if your application is only used in North America, the rest of the world will probably not thank you for this design decision.

Convert a string to a byte[]

// Native C# strings are unicode encoded
string StringMessage = "Hello World How Are you? Pi \u03C0 Yen \uFFE5";

// We can show the characters on the command line
Console.WriteLine("{0}", StringMessage);

// We can convert directly a byte array, but some information is lost
System.Text.ASCIIEncoding ASCII  = new System.Text.ASCIIEncoding();
Byte[] BytesMessage = ASCII.GetBytes(StringMessage);

To convert a byte[] back into a string

Byte[] BytesMessage; // Your message
System.Text.ASCIIEncoding ASCII  = new System.Text.ASCIIEncoding();
String StringMessage = ASCII.GetString( BytesMessage );

Solution #2 – Convert the Unicode string to a Unicode ASCII representation / String to encoded byte[]

These days a Western web browser can read Chinese pages, and send and receive e-mails to and from anywhere. But as many existing systems (including e-mail!) still limit transmission to the ASCII set of characters a number of standards exist to encode the 16 bit Unicode strings into 7 or 8 bit communication. The most commonly used encoding method is UTF-8 which reliably combines Unicode into 8 bit data.

Convert a string to a UTF-8 encoded byte[]

// Native C# strings are unicode encoded
string StringMessage = "Hello World How Are you? Pi \u03C0 Yen \uFFE5";

// We can convert directly a byte array
System.Text.UTF8Encoding UTF8 = new System.Text.UTF8Encoding();
Byte[] BytesMessage = UTF8.GetBytes(StringMessage);

Convert a UTF-8 Byte Array back into a string

Byte[] BytesMessage; // Your message
System.Text.UTF8Encoding UTF8 = new System.Text.UTF8Encoding();
String StringMessage = UTF8.GetString( BytesMessage );

As a side note: a UTF-8 encoded unicode character does not simply translate to 2 bytes. So the length of the created Byte[] is not simply 2 times the number of characters in the string.

In fact each Unicode character can possibly be encoded as 1 – 4 bytes. If you would like to know more about the encoding scheme, have a look at the Wikipedia UTF-8 page.

Image credit: roland

This is a post from Martijn's C# Coding Blog.

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