diff --git a/csharp/src/AddressBook/AddPerson.cs b/csharp/src/AddressBook/AddPerson.cs
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+++ b/csharp/src/AddressBook/AddPerson.cs
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+﻿#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using System;
+using System.IO;
+
+namespace Google.Protobuf.Examples.AddressBook
+{
+    internal class AddPerson
+    {
+        /// <summary>
+        /// Builds a person based on user input
+        /// </summary>
+        private static Person PromptForAddress(TextReader input, TextWriter output)
+        {
+            Person person = new Person();
+
+            output.Write("Enter person ID: ");
+            person.Id = int.Parse(input.ReadLine());
+
+            output.Write("Enter name: ");
+            person.Name = input.ReadLine();
+
+            output.Write("Enter email address (blank for none): ");
+            string email = input.ReadLine();
+            if (email.Length > 0)
+            {
+                person.Email = email;
+            }
+
+            while (true)
+            {
+                output.Write("Enter a phone number (or leave blank to finish): ");
+                string number = input.ReadLine();
+                if (number.Length == 0)
+                {
+                    break;
+                }
+
+                Person.Types.PhoneNumber phoneNumber = new Person.Types.PhoneNumber { Number = number };
+
+                output.Write("Is this a mobile, home, or work phone? ");
+                String type = input.ReadLine();
+                switch (type)
+                {
+                    case "mobile":
+                        phoneNumber.Type = Person.Types.PhoneType.MOBILE;
+                        break;
+                    case "home":
+                        phoneNumber.Type = Person.Types.PhoneType.HOME;
+                        break;
+                    case "work":
+                        phoneNumber.Type = Person.Types.PhoneType.WORK;
+                        break;
+                    default:
+                        output.Write("Unknown phone type. Using default.");
+                        break;
+                }
+
+                person.Phones.Add(phoneNumber);
+            }
+            return person;
+        }
+
+        /// <summary>
+        /// Entry point - loads an existing addressbook or creates a new one,
+        /// then writes it back to the file.
+        /// </summary>
+        public static int Main(string[] args)
+        {
+            if (args.Length != 1)
+            {
+                Console.Error.WriteLine("Usage:  AddPerson ADDRESS_BOOK_FILE");
+                return -1;
+            }
+
+            AddressBook addressBook;
+
+            if (File.Exists(args[0]))
+            {
+                using (Stream file = File.OpenRead(args[0]))
+                {
+                    addressBook = AddressBook.Parser.ParseFrom(file);
+                }
+            }
+            else
+            {
+                Console.WriteLine("{0}: File not found. Creating a new file.", args[0]);
+                addressBook = new AddressBook();
+            }
+
+            // Add an address.
+            addressBook.People.Add(PromptForAddress(Console.In, Console.Out));
+
+            // Write the new address book back to disk.
+            using (Stream output = File.OpenWrite(args[0]))
+            {
+                addressBook.WriteTo(output);
+            }
+            return 0;
+        }
+    }
+}
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