C Sharp

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\( \newcommand{\P}[]{\unicode{xB6}} \newcommand{\AA}[]{\unicode{x212B}} \newcommand{\empty}[]{\emptyset} \newcommand{\O}[]{\emptyset} \newcommand{\Alpha}[]{Α} \newcommand{\Beta}[]{Β} \newcommand{\Epsilon}[]{Ε} \newcommand{\Iota}[]{Ι} \newcommand{\Kappa}[]{Κ} \newcommand{\Rho}[]{Ρ} \newcommand{\Tau}[]{Τ} \newcommand{\Zeta}[]{Ζ} \newcommand{\Mu}[]{\unicode{x039C}} \newcommand{\Chi}[]{Χ} \newcommand{\Eta}[]{\unicode{x0397}} \newcommand{\Nu}[]{\unicode{x039D}} \newcommand{\Omicron}[]{\unicode{x039F}} \DeclareMathOperator{\sgn}{sgn} \def\oiint{\mathop{\vcenter{\mathchoice{\huge\unicode{x222F}\,}{\unicode{x222F}}{\unicode{x222F}}{\unicode{x222F}}}\,}\nolimits} \def\oiiint{\mathop{\vcenter{\mathchoice{\huge\unicode{x2230}\,}{\unicode{x2230}}{\unicode{x2230}}{\unicode{x2230}}}\,}\nolimits} \)


Usage

Regular Expressions

Regex
Reference

using System;
using System.Text.RegularExpressions;

public class Test
{
    public static void Main ()
    {
        // Define a regular expression for repeated words.
        Regex rx = new Regex(@"\b(?<word>\w+)\s+(\k<word>)\b");

        // Define a test string.      <br />
        string text = "The the quick brown fox  fox jumps over the lazy dog dog.";
      <br />
        // Find match.
        Match match = rx.Match(text);

        // Iterature through captures
        foreach (Capture c in match.captures) {
           Console.WriteLine("Captured {c.Value}");
        }
    }	
}

Multithreading

Theadpool

C# has a convenient TheadPool class in the System.Threading namespace.

class TestClass {
  static void Main(string[] args) {

    int numberOfTasks = 10;
    int tasksRemaining = 10;
    // This is similar to a mutex.
    ManualResetEvent finishedHandle = new ManualResetEvent(false);
    for (int i = 0; i < numberOfTasks; i++) {
      // Note that you cannot reuse i here.
      // You can use this trick to put it in a closure
      // Or you can make a closure manually with another anonymous function
      // i.e. (a => { return _=>{ \\ Do stuff here })(a)
      int j = i;
      ThreadPool.QueueUserWorkItem(_ => {
        try {
          // Do something time consuming or resource intensive.
          // Do not use i here. You can use j instead.
        } catch (System.Exception e) {
          // Print Stack Trace
        } finally {
          if (Interlocked.Decrement(ref tasksRemaining) == 0) {
            finishedHandle.Set();
          }
        }
      });
    }

    // Blocking wait.
    finishedHandle.WaitOne();
  }
}

Platform Invoke

Reference
Platform Invoke (or P/Invoke) allows you to call and use C and C++ libraries from within your C# or other .NET programs.