In this part of my C# tutorial I’ll cover threads in depth. With threads you can execute multiple pieces of code that share resources and data without corrupting it. I cover a simple thread example, sleep, a more advanced with lock, Priority, and how to pass data to a thread.

For best results take notes on the cheat sheet provided above as you watch and leave any questions you have.

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Code & Transcript

using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
using System.Threading;

namespace CSharpTutA.cs
{
    // With threads you can execute multiple
    // pieces of code that share resources
    // and data without corrupting it

    // You can't guarantee when a thread
    // executes. You also must lock resources
    // until a thread is done with them
    // or you could corrupt them

    class Program
    {
        // ----- Simple Thread Example -----
        /*
        static void Main(string[] args)
        {
            // Create a thread and start it
            Thread t = new Thread(Print1);
            t.Start();

            // This code will run randomly
            for (int i = 0; i < 1000; i++)
                Console.Write(0);

            Console.ReadLine();

        }

        static void Print1()
        {
            for (int i = 0; i < 1000; i++)
                Console.Write(1);
        }
        

        // ----- Sleep Example -----

        // With sleep() the thread is suspended
        // for the designated amount of time
        static void Main(string[] args)
        {
            int num = 1;
            for (int i = 0; i < 10; i++)
            {
                Console.WriteLine(num);

                // Pause for 1 second
                Thread.Sleep(1000);

                num++;
            }

            Console.WriteLine("Thread Ends");

            Console.ReadLine();
        }

        // ----- Lock Example -----
        // lock keeps other threads from entering 
        // a statement block until another thread
        // leaves
        static void Main(string[] args)
        {
            BankAcct acct = new BankAcct(10);
            Thread[] threads = new Thread[15];

            // CurrentThread gets you the current
            // executing thread
            Thread.CurrentThread.Name = "main";

            // Create 15 threads that will call for 
            // IssueWithdraw to execute
            for (int i = 0; i < 15; i++)
            {
                // You can only point at methods
                // without arguments and that return 
                // nothing
                Thread t = new Thread(new 
                    ThreadStart(acct.IssueWithdraw));
                t.Name = i.ToString();
                threads[i] = t;
            }

            // Have threads try to execute
            for (int i = 0; i < 15; i++)
            {
                // Check if thread has started
                Console.WriteLine("Thread {0} Alive : {1}",
                    threads[i].Name, threads[i].IsAlive);

                // Start thread
                threads[i].Start();

                // Check if thread has started
                Console.WriteLine("Thread {0} Alive : {1}",
                    threads[i].Name, threads[i].IsAlive);
            }

            // Get thread priority (Normal Default)
            // Also Lowest, BelowNormal, AboveNormal
            // and Highest
            // Changin priority doesn't guarantee
            // the highest precedence though
            // It is best to not mess with this
            Console.WriteLine("Current Priority : {0}",
                Thread.CurrentThread.Priority);

            Console.WriteLine("Thread {0} Ending",
                Thread.CurrentThread.Name);

            Console.ReadLine();
        }
    }
}

class BankAcct
{
    private Object acctLock = new Object();
    double Balance { get; set; }
    string Name { get; set; }

    public BankAcct(double bal)
    {
        Balance = bal;
    }

    public double Withdraw(double amt)
    {
        if((Balance - amt) < 0)
        {
            Console.WriteLine($"Sorry ${Balance} in Account");
            return Balance;
        }

        lock (acctLock)
        {
            if(Balance >= amt)
            {
                Console.WriteLine("Removed {0} and {1} left in Account",
                amt, (Balance - amt));
                Balance -= amt;
            }
            
            return Balance;
            
        }
    }

    // You can only point at methods
    // without arguments and that return 
    // nothing
    public void IssueWithdraw()
    { 
        Withdraw(1);
    }
}
*/

        // ----- Passing Data to Threads -----
        // You can pass arguments to a thread 
        // using a lambda expression

        static void Main(string[] args)
        {
            Thread t = new Thread(() => CountTo(10));
            t.Start();

            // You can use multiline lambdas
            new Thread(() =>
            {
                CountTo(5);
                CountTo(6);
            }).Start();

            Console.ReadLine();
        }

        static void CountTo(int maxNum)
        {
            for(int i = 0; i <= maxNum; i++)
            {
                Console.WriteLine(i);
            }
        }

    }
}