# C# Programs

C# programs are frequently asked in the interview. These programs can be asked from basics, array, string, control statements, file handling etc. Let's see the list of top C# programs.

## 1) Fibonacci Series

Write a c# program to print fibonacci series without using recursion and using recursion.

Input: 15

Output: 0 1 1 2 3 5 8 13 21 34 55 89 144 233 377

## 2) Prime number

Write a c# program to check prime number.

Input: 17

Output: prime number

Input: 57

Output: not prime number

## 3) Palindrome number

Write a c# program to check palindrome number.

Input: 121

Output: palindrome number

Input: 113

Output: not palindrome number

## 4) Factorial

Write a c# program to print factorial of a number.

Input: 6

Output: 720

## 5) Armstrong number

Write a c# program to check armstrong number.

Input: 371

Output: armstrong

Input: 342

Output: not armstrong

## 6) Sum of Digits

Write a c# program to print sum of digits.

Input: 23

Output: 5

Input: 624

Output: 12

## 7) Reverse Number

Write a c# program to reverse given number.

Input: 234

Output: 432

## 8) Swap two numbers without using third variable

Write a c# program to swap two numbers without using third variable.

Input: a=5 b=10

Output: a=10 b=5

## 9) Decimal to Binary

Write a c# program to convert decimal number to binary.

Input: 10

Output: 1010

## 10) Alphabet Triangle

Write a c# program to print alphabet triangle.

Output:

```     A
ABA
ABCBA
ABCDCBA
ABCDEDCBA
```

## 11) Number Triangle

Write a c# program to print number triangle.

Input: 5

Output:

```enter the range= 6
1
121
2321
1234321
123454321
12345654321
```

## 12) Fibonacci Triangle

Write a c# program to generate fibonacci triangle.

Input: 9

Output:

```1
1	1
1	1	2
1	1	2	3
1	1	2	3	5
1	1	2	3	5	8
1	1	2	3	5	8	13
1	1	2	3	5	8	13	21
1	1	2	3	5	8	13	21	34

```

## 13) Number in Characters

Write a c# program to convert number in characters.

Input: 357546

Output:three five seven five four six    