September 2017 Update

Task/Function-prototype/C-sharp/function-prototype-1.cs

@@ -0,0 +1,12 @@
+using System;
+abstract class Printer
+{
+    public abstract void Print();
+}
+
+class PrinterImpl : Printer
+{
+    public override void Print() {
+        Console.WriteLine("Hello world!");
+    }
+}

Task/Function-prototype/C-sharp/function-prototype-2.cs

@@ -0,0 +1,22 @@
+using System;
+public delegate int IntFunction(int a, int b);
+
+public class Program
+{
+    public static int Add(int x, int y) {
+        return x + y;
+    }
+
+    public static int Multiply(int x, int y) {
+        return x * y;
+    }
+
+    public static void Main() {
+        IntFunction func = Add;
+        Console.WriteLine(func(2, 3)); //prints 5
+        func = Multiply;
+        Console.WriteLine(func(2, 3)); //prints 6
+        func += Add;
+        Console.WriteLine(func(2, 3)); //prints 5. Both functions are called, but only the last result is kept.
+    }
+}

Task/Function-prototype/C-sharp/function-prototype-3.cs

@@ -0,0 +1,20 @@
+//file1.cs
+public partial class Program
+{
+    partial void Print();
+}
+
+//file2.cs
+using System;
+
+public partial class Program
+{
+    partial void Print() {
+        Console.WriteLine("Hello world!");
+    }
+
+    static void Main() {
+        Program p = new Program();
+        p.Print(); //If the implementation above is not written, the compiler will remove this line.
+    }
+}