Part 91 - Retrieving data from Thread function using callback method

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Part 88 - ThreadStart delegate
Part 89 - ParameterizedThreadStart delegate
Part 90 - Passing data to the Thread function in a type safe manner



In this video we will discuss, retrieving data from Thread function using callback method. This is continuation to Part 90. Please watch Part 90 before proceeding. We will be working with the same example we worked with in Part 90.

using System;

using System.Threading; 

namespace ThreadStartDelegateExample

{

    // Step 1: Create a callback delegate. The actual callback method

    // signature should match with the signature of this delegate.

    public delegate void SumOfNumbersCallback(int sumOfNumbers);

    // Step 2: Create Number class to compute the sum of numbers and

    // to call the callback method

    class Number

    {

        // The traget number this class needs to compute the sum of numbers

        int _target;

        // Delegate to call when the the Thread function completes                 
        // computing the sum of numbers

        SumOfNumbersCallback _callbackMethod;

        // Constructor to initialize the target number and the callback delegateinitialize

        public Number(int target, SumOfNumbersCallback callbackMethod)

        {

            this._target = target;

            this._callbackMethod = callbackMethod;

        }

        // This thread function computes the sum of numbers and then invokes

        // the callback method passing it the sum of numbers

        public void ComputeSumOfNumbers()

        {

            int sum = 0;

            for (int i = 1; i <= _target; i++)

            {

                sum = sum + i;

            }

            if (_callbackMethod != null)

            {

                _callbackMethod(sum);

            }

        }

    }

    // Step 3: This class consumes the Number class created in Step 2

    class Program

    {

        // Callback method that will receive the sum of numbers

        public static void PrintSumOfNumbers(int sum)

        {

            Console.WriteLine("Sum of numbers is " + sum);

        }

        public static void Main()

        {

            // Prompt the user for the target number

            Console.WriteLine("Please enter the target number");

            // Read from the console and store it in target variable

            int target = Convert.ToInt32(Console.ReadLine());

            // Create an instance of callback delegate and to it's constructor

            // pass the name of the callback function (PrintSumOfNumbers)

            SumOfNumbersCallback callbackMethod = new SumOfNumbersCallback(PrintSumOfNumbers);

            // Create an instance of Number class and to it's constrcutor pass the target

            // number and the instance of callback delegate

            Number number = new Number(target, callbackMethod);

            // Create an instance of Thread class and specify the Thread function to invoke

            Thread T1 = new Thread(new ThreadStart(number.ComputeSumOfNumbers));

            T1.Start();

        }

    }

}