Check number in C#

In C#, you can identify if a string is a number, extract a number from a string, check if the console input is a number, and check if an integer is a power of 2 using various methods. Here are some examples:

Identifying if a String is a Number

string input = "123";
bool isNumber = int.TryParse(input, out int result);

In this example, the int.TryParse method is called with the input variable as the first argument, and an out variable result of type int as the second argument. The TryParse method attempts to parse the input string as an integer and stores the result in the result variable. If the parse operation is successful, the method returns true, indicating that the input string is a number.

Extracting a Number from a String

string input = "abc123def";
string numberString = new string(input.Where(char.IsDigit).ToArray());
int number = int.Parse(numberString);

In this example, the input variable contains a string that contains a number. The Where LINQ extension method is called on the input string to filter out all non-digit characters, and the resulting characters are converted to a new string using the new string constructor. The resulting string is then parsed as an integer using the int.Parse method.

Checking if the Console Input is a Number

Console.Write("Enter a number: ");
string input = Console.ReadLine();
bool isNumber = int.TryParse(input, out int result);
if (isNumber) {
    Console.WriteLine("Input is a number: " + result);
} else {
    Console.WriteLine("Input is not a number");
}

In this example, the Console.ReadLine method is called to read a string input from the console. The int.TryParse method is then called with the input string as the first argument, and an out variable result of type int as the second argument. The TryParse method attempts to parse the input string as an integer and stores the result in the result variable. If the parse operation is successful, the isNumber variable is set to true, and the result is printed to the console. If the parse operation fails, the isNumber variable is set to false, and a message indicating that the input is not a number is printed to the console.

Checking if an Integer is a Power of 2

int number = 8;
bool isPowerOfTwo = (number != 0) && ((number & (number - 1)) == 0);

In this example, the number variable contains an integer value. The isPowerOfTwo variable is set to true if the number variable is not equal to zero and the bitwise AND operation between number and number - 1 is equal to zero. This is because a power of 2 has only one bit set, and the bitwise AND of a power of 2 and the power of 2 minus 1 will always be zero.

C# check if a number is positive/negative

int number = 42;
bool isPositive = (number > 0);
bool isNegative = (number < 0);

Checking if a number is even or odd in C#

int number = 42;
bool isEven = (number % 2 == 0);
bool isOdd = (number % 2 != 0);

C# check if a number is prime

int number = 7;
bool isPrime = Enumerable.Range(2, (int)Math.Sqrt(number) - 1).All(i => number % i > 0);

Validating integer range in C#

int number = 42;
bool isInRange = (number >= minValue && number <= maxValue);

Detecting integer overflow in C#

checked
{
    int result = int.MaxValue + 1;  // Throws OverflowException
}

C# check if a number is NaN or Infinity

double result = 0.0 / 0.0;
bool isNaN = double.IsNaN(result);
bool isInfinity = double.IsInfinity(result);

Checking for divisibility in C#

int number = 42;
bool isDivisibleBy3 = (number % 3 == 0);

C# check if a number is a power of two

int number = 64;
bool isPowerOfTwo = (number & (number - 1)) == 0;

Validating decimal precision in C#

decimal number = 123.456m;
bool hasValidPrecision = (number % 1 == 0);

C# check if a number is a perfect square

int number = 16;
double squareRoot = Math.Sqrt(number);
bool isPerfectSquare = squareRoot % 1 == 0;

C# check if a number is within a tolerance

double expectedValue = 10.0;
double actualValue = 10.00001;
double tolerance = 0.001;
bool isWithinTolerance = Math.Abs(expectedValue - actualValue) < tolerance;

C# check if a number is a Fibonacci number

int number = 21;
bool isFibonacci = IsPerfectSquare(5 * number * number + 4) || IsPerfectSquare(5 * number * number - 4);

static bool IsPerfectSquare(int x)
{
    int sqrt = (int)Math.Sqrt(x);
    return sqrt * sqrt == x;
}

C# check if a number is a multiple of another

int number = 15;
int multipleOf = 3;
bool isMultiple = (number % multipleOf == 0);

C# check if a number is a palindrome

int number = 1221;
string numberString = number.ToString();
bool isPalindrome = numberString.SequenceEqual(numberString.Reverse());

Detecting numeric overflow in C#
Overflow can occur during arithmetic operations on numeric types, especially when using checked keyword.
```
checked
{
    int result = int.MaxValue * 2;  // Throws OverflowException
}
```