Prime Number Improvements, Moved the methods into a unique class. The list has been exchanged for a single string with line breaks. This is much more efficient and doesnt require the foreach loop to output the data. Can just output the single string.

Prime Numbers (Efficient)/Prime Numbers (Efficient)/Prime Numbers (Efficient).csproj

@@ -43,6 +43,7 @@
     <Reference Include="System.Xml" />
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="prime.cs" />
     <Compile Include="Program.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
   </ItemGroup>

Prime Numbers (Efficient)/Prime Numbers (Efficient)/Program.cs

@@ -10,36 +10,9 @@ namespace Prime_Numbers__Efficient_
     {
         static void Main(string[] args)
         {
-            int startNum = 2;
+            prime primeFinder = new prime();
-            int maxNum = Convert.ToInt32(Console.ReadLine());
-            bool isPrime = true;
-            List<int> primeList = new List<int>();
 
-            for (int x = startNum; x <= maxNum; x++)
+            Console.WriteLine(primeFinder.getPrimes(2, 2000000));
-            {
-                for (int y = 2; y < (x / 2) + 1; y++)
-                {
-                    if ((x % y == 0))
-                    {
-                        isPrime = false;
-                        break;
-                    }
-                }
-                if (isPrime == true)
-                {
-                    primeList.Add(x);
-                }
-                else
-                {
-                    isPrime = true;
-                }
-                
-            }
-
-            foreach (var item in primeList)
-            {
-                Console.WriteLine(item);
-            }
 
             Console.ReadLine();
 

Prime Numbers (Efficient)/Prime Numbers (Efficient)/prime.cs

@@ -0,0 +1,43 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Prime_Numbers__Efficient_
+{
+    class prime
+    {
+        //Prime until proven not prime
+        private bool IsPrime { get; set; } = true;
+        private string Primes { get; set; }
+
+        public string getPrimes(int startNum, int endNum)
+        {
+            for (int x = startNum; x <= endNum; x++)
+            {
+                for (int y = 2; y < (x / 2) + 1; y++)
+                {
+                    if ((x % y == 0))
+                    {
+                        IsPrime = false;
+                        break;
+                    }
+                }
+                if (IsPrime == true)
+                {
+                    Primes += x + "\n";
+                }
+                else
+                {
+                    IsPrime = true;
+                }
+
+            }
+
+            return Primes;
+
+        }    
+
+    }
+}