Add C# implementaion of 86 Target

86 Target/csharp/Target/Input.cs

@@ -0,0 +1,59 @@
+using System;
+using System.Collections.Generic;
+
+namespace Target
+{
+    // Provides input methods which emulate the BASIC interpreter's keyboard input routines
+    internal static class Input
+    {
+        internal static void Prompt(string text = "") => Console.Write($"{text}? ");
+
+        internal static List<float> ReadNumbers(string prompt, int requiredCount)
+        {
+            var numbers = new List<float>();
+
+            while (!TryReadNumbers(prompt, requiredCount, numbers))
+            {
+                numbers.Clear();
+                prompt = "";
+            }
+
+            return numbers;
+        }
+
+        private static bool TryReadNumbers(string prompt, int requiredCount, List<float> numbers)
+        {
+            Prompt(prompt);
+            var inputValues = ReadStrings();
+
+            foreach (var value in inputValues)
+            {
+                if (numbers.Count == requiredCount)
+                {
+                    Console.WriteLine("!Extra input ingored");
+                    break;
+                }
+
+                if (!TryParseNumber(value, out var number))
+                {
+                    return false;
+                }
+
+                numbers.Add(number);
+            }
+
+            return numbers.Count == requiredCount || TryReadNumbers("?", requiredCount, numbers);
+        }
+
+        private static string[] ReadStrings() => Console.ReadLine().Split(',', StringSplitOptions.TrimEntries);
+
+        private static bool TryParseNumber(string text, out float number)
+        {
+            if (float.TryParse(text, out number)) { return true; }
+
+            Console.WriteLine("!Number expected - retry input line");
+            number = default;
+            return false;
+        }
+    }
+}