1.8. C# constant

1.8.1. Integer constant #

Integer constants can be decimal, octal or hexadecimal constants. The prefix specifies the cardinality: 0x or 0X for hexadecimal, 0 for octal, and no prefix for decimal.

Integer constants can also have suffixes, which can be a combination of U and L, where U and L represent respectively unsigned and long . Suffixes can be uppercase or lowercase, and multiple suffixes are combined in any order.

Here are some examples of integer constants:

212         /* legal */
215u        /* legal */
0xFeeL      /* legal */
078         /* illegal：8 Not an octal number */
032UU       /* Illegal: cannot duplicate suffix */

The following are examples of various types of integer constants:

85         /* decimalism */
0213       /* Octal */
0x4b       /* hexadecimal */
30         /* int */
30u        /* Unsigned int */
30l        /* long */
30ul       /* Unsigned long */

1.8.2. Floating point constant #

A floating-point constant consists of an integer part, a decimal point, a decimal part, and an exponential part. You can represent floating-point constants in either decimal or exponential form.

Here are some examples of floating point constants:

3.14159       /* legal */
314159E-5L    /* legal */
510E          /* Illegal: incomplete index */
210f          /* Illegal: No decimals or indices */
.e55          /* Illegal: missing integer or decimal */

When represented in floating-point form, you must include a decimal point, an exponent, or both. When expressed in exponential form, it must contain an integer part, a decimal part, or both. Signed exponents are represented bye or E.

1.8.3. Character constant #

Character constants are enclosed in single quotation marks, such as 'x' can be stored in a simple character type variable, a character constant can be a normal character ( 'x' ), an escape sequence(for example, '\t' ) or a common character (for example '\u02C0' ).

There are specific characters in C # that have a special meaning when preceded by a backslash and can be used to indicate a newline character (n) or a tab character tab (t). Here, list some escape sequence codes:

Here are some examples of escape sequence characters:

namespace EscapeChar
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello\tWorld\n\n");
            Console.ReadLine();
        }
    }
}

When the above code is compiled and executed, it produces the following results:

Hello   World

1.8.4. String constant #

String constants are enclosed in double quotation marks "" , or included in @"" . String constants contain characters similar to character constants, which can be: ordinary characters, escape sequences, and general characters

When using string constants, you can split a long line into multiple lines, and you can separate parts with spaces.

Here are some examples of string constants. The various forms listed below represent the same string.

string a = "hello, world";                  // hello, world
string b = @"hello, world";               // hello, world
string c = "hello \t world";               // hello     world
string d = @"hello \t world";               // hello \t world
string e = "Joe said \"Hello\" to me";      // Joe said "Hello" to me
string f = @"Joe said ""Hello"" to me";   // Joe said "Hello" to me
string g = "\\\\server\\share\\file.txt";   // \\server\share\file.txt
string h = @"\\server\share\file.txt";      // \\server\share\file.txt
string i = "one\r\ntwo\r\nthree";
string j = @"one
two
three";

1.8.5. Define constant #

Constant is to use the const keyword to define it. The syntax for defining a constant is as follows:

const <data_type> <constant_name> = value;

The following code demonstrates how to define and use constants in a program:

using System;
public class ConstTest
{
    class SampleClass
    {
        public int x;
        public int y;
        public const int c1 = 5;
        public const int c2 = c1 + 5;
        public SampleClass(int p1, int p2)
        {
            x = p1;
            y = p2;
        }
    }
    static void Main()
    {
        SampleClass mC = new SampleClass(11, 22);
        Console.WriteLine("x = {0}, y = {1}", mC.x, mC.y);
        Console.WriteLine("c1 = {0}, c2 = {1}",
                          SampleClass.c1, SampleClass.c2);
    }
}

x = 11, y = 22
c1 = 5, c2 = 10