Few Programs that would help in interviews, C#

Language: Layout:

//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
            //Few Programs that would help in interviews
            Console.WriteLine("Hello, Guys!");
            SwapTwoNumber(10,20);
            FibonacciSeries(10);
            StarPattern1(8);
            StarPattern2(8);
            StarPattern3(6, 7);
            var str = StringReversal("RAMA");
            
        }
        
        public static void SwapTwoNumber(int a, int b)
        {
            Console.WriteLine("Swap Two Numbers a={0}, b={1}",a,b);
            a = a+b;
            b = a-b;
            a = a-b;
            Console.WriteLine("After swapping a={0}, b={1}",a,b);
        }
        
        public static void FibonacciSeries(int count)
        {
            int a1=0; int a2=1; int a3=0;
            Console.WriteLine("Fibonacci Series");
            for(int i=0; i<=count ; i++)
            {
                a3=a1+a2;
                Console.WriteLine(a3);
                a1=a2;
                a2=a3;
            }
        }
        
        public static string StringReversal(string a)
        {
            Console.WriteLine("Reverse a String:{0}", a);
            char[] actual_str = a.ToCharArray();
            char[] reversed_str = new char[actual_str.Length];  
            int i= 0;
            for (int j = actual_str.Length - 1; i < actual_str.Length; j--) {  
                reversed_str[i] = actual_str[j];  
                i++;
            } 
            Console.WriteLine("Reversed String = {0}",new string(reversed_str));
            return new string(reversed_str);
        }
            
        public static void StarPattern1(int x)
        {
            Console.WriteLine("PATTERN 1");
            for(int rows =1; rows<=x; ++rows)
            {
                for(int col=1; col<=rows; ++col)
                {
                    Console.Write("*");
                }
                Console.WriteLine();
            }
        }
        
        public static void StarPattern2(int y)
        {
            Console.WriteLine("PATTERN 2");
            for(int rows=y; rows>=1 ; --rows)
            {
                for(int col=1; col<=rows; ++col)
                {
                    Console.Write("*");
                }
                Console.WriteLine();
            }
        }
        
        public static void StarPattern3(int x, int y)
        {
            //Combining two logics of Pattern 1 and Pattern 2
            Console.WriteLine("PATTERN 3");
            for(int rows =1; rows<=x; ++rows)
            {
                for(int col=1; col<=rows; ++col)
                {
                    Console.Write("*");
                }
                Console.WriteLine();
            }
            for(int rows=y; rows>=1 ; --rows)
            {
                for(int col=1; col<=rows; ++col)
                {
                    Console.Write("*");
                }
                Console.WriteLine();
            }
        }
    }
}

Show compiler warnings [ + ] Show input
Compilation time: 0,19 sec, absolute running time: 0,11 sec, cpu time: 0,09 sec, average memory usage: 13 Mb, average nr of threads: 3, absolute service time: 0,33 sec