create EvenFiboNumbers for Q2

Author: Prhmma

Diff for: C#/EvenFiboNumbers.cs

@@ -0,0 +1,48 @@
+using System;
+namespace _2._Even_Fibonacci_numbers
+{
+    class EvenFiboNumbers
+    {
+        static int evenFibSum(int limit)
+        {
+            if (limit < 2)
+                return 0;
+
+            // Initialize first two even 
+            // prime numbers and their sum 
+            long ef1 = 0, ef2 = 2;
+            long sum = ef1 + ef2;
+
+            // calculating sum of even  
+            // Fibonacci value 
+            while (ef2 <= limit)
+            {
+
+                // get next even value of  
+                // Fibonacci sequence 
+                long ef3 = 4 * ef2 + ef1;
+
+                // If we go beyond limit, 
+                // we break loop 
+                if (ef3 > limit)
+                    break;
+
+                // Move to next even number 
+                // and update sum 
+                ef1 = ef2;
+                ef2 = ef3;
+                sum += ef2;
+            }
+
+            return (int)sum;
+        }
+
+        // Driver code 
+        public static void Main()
+        {
+            int limit = 4000000;
+            Console.Write(evenFibSum(limit));
+
+        }
+    }
+}