# Write a C# Program to Print the Factorial of a Number

Do you want to print the factorial of a number in C#? In this tutorial, I will explain how to write a C# program to print the factorial of a number. I will show you how to write a C# program to find the factorial program in c# without using loop.

To calculate the factorial of a number in C#, you can use an iterative approach with a for loop. In the program, you first read the user’s input, then iterate from 2 up to the number, multiplying each value with a running total to obtain the factorial.

## Write a C# Program to Print the Factorial of a Number

The factorial of a non-negative integer n, denoted by n!, is the product of all positive integers less than or equal to n. For example, the factorial of 5 (5!) is 5 x 4 x 3 x 2 x 1 = 120.

We can calculate factorials in C# using either an iterative approach (using loops) or a recursive approach. For simplicity and better performance on larger numbers, we’ll use the iterative approach in this example.

Here’s the complete code to calculate the factorial of a number in C#:

using System;

class FactorialProgram
{
static void Main(string[] args)
{
Console.WriteLine("Enter a number to calculate its factorial:");

long factorial = CalculateFactorial(number);

Console.WriteLine(\$"The factorial of {number} is {factorial}.");
}

static long CalculateFactorial(int number)
{
if (number < 0)
{
throw new ArgumentException("Factorial of a negative number doesn't exist.");
}

long result = 1;
for (int i = 2; i <= number; i++)
{
result *= i;
}

return result;
}
}

Here is the complete code explanation:

• We start by importing the System namespace which is essential for basic input and output operations.
• The FactorialProgram class contains the Main method, which is the entry point of the program.
• Inside Main, we prompt the user to enter a number and read this input using Console.ReadLine().
• The CalculateFactorial method is then called to compute the factorial of the entered number. This method uses a loop to calculate the factorial iteratively.
• The program handles negative inputs by throwing an ArgumentException, as factorials for negative numbers are undefined.
• Finally, the factorial is printed to the console.

Once you run the code, it will ask you to enter a number, and then it will display the factorial of the number in the C# console application. Here is the screenshot for the output:

## Factorial program in c# without using loop

If you are looking to find the factorial of a number in C# without using loop, then check out the below program. The program is to get factorial program in c# without using loop.

In C#, apart from the iterative method for calculating the factorial of a number, you can also use the recursive approach. Recursive methods call themselves with a reduced parameter until they reach a base case. In the case of factorial calculation, the base case is when the number is 0 or 1, as the factorial of both is 1.

using System;

class FactorialProgram
{
static void Main(string[] args)
{
Console.WriteLine("Enter a number to calculate its factorial:");

long factorial = CalculateFactorialRecursive(number);

Console.WriteLine(\$"The factorial of {number} is {factorial}.");
}

static long CalculateFactorialRecursive(int number)
{
if (number < 0)
{
throw new ArgumentException("Factorial of a negative number doesn't exist.");
}
if (number == 0 || number == 1)
{
return 1;
}
return number * CalculateFactorialRecursive(number - 1);
}
}

Once you run the code using the Visual Studio C# console application, you can see the output like the screenshot below.

## Conclusion

This C# program is a basic demonstration of calculating factorials. It is an excellent example for beginners to understand loops and basic exception handling in C#. In this C# tutorial, I have explained how to write a C# program to print the factorial of a number.

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