functional-workshop

functional programming principles applied in C#

---

Project maintained by B1tF8er Hosted on GitHub Pages — Theme by mattgraham

Delegates

Delegates are the most basic form to use functions as first-class citizens in C#.

using System;
using System.Diagnostics;

internal static class TestDelegates
{
    // string -> ()
    private delegate void LoggerDelegate(string message);
    // string -> string
    private delegate string LoggerWithResponseDelegate(string message);

    internal static void Run()
    {
        RunVoidDelegates();
        RunResponseDelegates();
    }

    private static void RunVoidDelegates()
    {
        LoggerDelegate consoleLoggerHandler = ConsoleLogger;
        LoggerDelegate debugLoggerHandler = DebugLogger;
        LoggerDelegate allConsoleHandlers = consoleLoggerHandler + debugLoggerHandler;

        consoleLoggerHandler("This goes to the console");
        debugLoggerHandler("This goes to the debug");
        allConsoleHandlers("this goes to all");
    }

    private static void RunResponseDelegates()
    {
        LoggerWithResponseDelegate consoleLoggerHandler = ConsoleLoggerWithResponse;
        LoggerWithResponseDelegate debugLoggerHandler = DebugLoggerWithResponse;
        LoggerWithResponseDelegate allConsoleHandlers = consoleLoggerHandler + debugLoggerHandler;

        var consoleResponse = consoleLoggerHandler("This goes to the console");
        var debugResponse = debugLoggerHandler("This goes to the debug");
        var lastResponse = allConsoleHandlers("this goes to all");
    }

    private static void ConsoleLogger(string message) => Console.WriteLine(message);

    private static void DebugLogger(string message) => Debug.WriteLine(message);

    private static string ConsoleLoggerWithResponse(string message)
    {
        Console.WriteLine(message);
        return "Logged to console";
    }

    private static string DebugLoggerWithResponse(string message)
    {
        Debug.WriteLine(message);
        return "Logged to debug";
    }
}