Find Prime number, C#

Find Prime number

//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)
        {
            //pri
             int n =5;
            findPrimeNumberApproach1(n);
            findPrimeNumberApproach2(n);
            bool b = findPrimeNumberApproach3(n);
             if(b) {
                   Console.WriteLine("{0} is a Prime Number", n);
             } else {
                    Console.WriteLine("{0} is not a Prime Number", n);
             }
        }
        
         public static void findPrimeNumberApproach1(int n) {
                bool isPrime = true;
                int m = n/2; 
                 if (n <= 1 )
                     isPrime = false;

for (int i = 2; i <= m; i++) {
                         if (n % i == 0){
                             isPrime =  false;
                         }
                     }

if(isPrime) {
                   Console.WriteLine("{0} is a Prime Number", n);
                } else {
                    Console.WriteLine("{0}  is not a Prime Number", n);
                }
                
         }
        public static void findPrimeNumberApproach2(int n) {
            int count = 0;
            for (int i = 1; i <= n; i++) {
                if (n % i == 0) {
                   count++;
                }
             }
             if (count == 2) {
                Console.WriteLine("{0} is a Prime Number", n);
             } else {
                Console.WriteLine("{0}  is not a Prime Number", n);
             }
        }
        
        internal static bool findPrimeNumberApproach3(int number)  {  
              if (number == 1) return false;  
              if (number == 2) return true;  
              if (number % 2 == 0) return false;

var squareRoot = (int)Math.Floor(Math.Sqrt(number));  
              for (int i = 3; i <= squareRoot; i += 2)  {  
                  if (number % i == 0) return false;  
              }  
              return true;  
          }  
    }
}


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