Numbers in C#

In C#, you can convert decimal values to double values using explicit casting or the Convert method. Here's how to do it:

Converting Decimal to Double

decimal decimalValue = 10.5m;
double doubleValue1 = (double)decimalValue;
double doubleValue2 = Convert.ToDouble(decimalValue);

In this example, the decimalValue variable is explicitly cast to a double using the (double) syntax. Alternatively, the Convert.ToDouble method is called with the decimalValue variable as the argument to convert it to a double.

Converting Decimal Array to Double Array

decimal[] decimalArray = { 1.1m, 2.2m, 3.3m };
double[] doubleArray = decimalArray.Select(x => (double)x).ToArray();

In this example, the decimalArray variable is converted to a double array using LINQ's Select method to perform an explicit cast on each element, and then ToArray is called to convert the resulting IEnumerable<double> to a double[].

Converting decimal[][] to double[][]

decimal[][] decimalArray2D = { new decimal[] { 1.1m, 2.2m }, new decimal[] { 3.3m, 4.4m } };
double[][] doubleArray2D = decimalArray2D.Select(x => x.Select(y => (double)y).ToArray()).ToArray();

In this example, the decimalArray2D variable is converted to a double array using LINQ's Select method to perform an explicit cast on each element of the inner arrays, and then ToArray is called to convert the resulting IEnumerable<double> to a double[]. Finally, another ToArray is called on the resulting IEnumerable<double[]> to convert it to a double[][].

Rounding a Number to Two Decimal Places

double value = 10.56789;
double roundedValue = Math.Round(value, 2);

In this example, the Math.Round method is called with the value variable as the first argument, and 2 as the second argument to round the value to two decimal places.

Converting Char to Int

char charValue = '5';
int intValue = (int)charValue - (int)'0';

In this example, the charValue variable is explicitly cast to an int, and then the integer value of the character '0' is subtracted to convert the resulting value to an integer. Note that this method assumes that the charValue variable contains a single digit character between '0' and '9'.

Working with integers in C#
```
int a = 5;
int b = 3;
int sum = a + b;
```

C# floating-point numbers

float floatValue = 3.14f;
double doubleValue = 3.14159265359;

Arithmetic operations in C#

int result = 5 + 3;  // Addition
int difference = 5 - 3;  // Subtraction
int product = 5 * 3;  // Multiplication
int quotient = 5 / 3;  // Division (integer division)
int remainder = 5 % 3;  // Modulo (remainder)

C# mathematical functions
C# provides various mathematical functions in the Math class:
```
double squareRoot = Math.Sqrt(25);
double power = Math.Pow(2, 3);
```

Parsing and formatting numbers in C#

string numberString = "42";
int parsedNumber = int.Parse(numberString);

int number = 42;
string formattedNumber = number.ToString();

C# random number generation

Random random = new Random();
int randomNumber = random.Next(1, 101);  // Generates a random number between 1 and 100

Working with decimals in C#
```
decimal decimalNumber = 3.14m;
```

C# bitwise operations on numbers

int x = 5;  // 0101 in binary
int y = 3;  // 0011 in binary

int resultAnd = x & y;  // Bitwise AND: 0001
int resultOr = x | y;   // Bitwise OR: 0111
int resultXor = x ^ y;  // Bitwise XOR: 0110

C# rounding and precision

double value = 3.14159;
double roundedValue = Math.Round(value, 2);  // Rounds to 2 decimal places

Number formatting in C#

int number = 1234567;
string formattedNumber = number.ToString("N");  // Adds commas: 1,234,567

C# converting between numeric types

int intValue = 42;
double doubleValue = Convert.ToDouble(intValue);

BigInteger in C# for large numbers

BigInteger bigIntegerValue = BigInteger.Parse("1234567890123456789012345678901234567890");

C# NaN and Infinity handling

double result = 0.0 / 0.0;  // NaN
double positiveInfinity = 1.0 / 0.0;  // Positive Infinity
double negativeInfinity = -1.0 / 0.0;  // Negative Infinity

Number comparison in C#

int a = 5;
int b = 3;

bool isEqual = a == b;
bool isNotEqual = a != b;

C# checking if a number is even or odd

int number = 42;

bool isEven = (number % 2 == 0);
bool isOdd = (number % 2 != 0);

Hexadecimal and binary representation of numbers in C#

int hexValue = 0x1A;  // Hexadecimal
int binaryValue = 0b1010;  // Binary

C# trigonometric functions

double angleInRadians = Math.PI / 4;
double sineValue = Math.Sin(angleInRadians);
double cosineValue = Math.Cos(angleInRadians);

Number manipulation libraries in C#
Libraries like System.Numerics provide advanced numeric types and operations.