Update Int32 in Task c#

Question

is there any way to increment a value of an int inside a task? or is this a correct syntax in incrementing an int in task? sample code:

public int erCount = 9;
static void Main(string[] args){
    Task.Factory.StartNew(() => { 
        ...do some task
        if(errorfound)
            erCount++;
    });
    Task.Wait();
    Console.Writeline(erCount.toString());
}

I seem not to get it in incrementing value inside a thread. Any help would be great!

Answer 1

Your code is fine as long as you're not modifying the erCount in multiple threads. In which case you'd need a lock or Interlocked.Increment .

Your problem is you're not waiting for the started Task to complete.

public static int erCount = 9;
static void Main(string[] args)
{
    var task = Task.Factory.StartNew(() => 
    { 
        ...do some task
        if(errorfound)
            Interlocked.Increment(ref erCount);
    });
    task.Wait();//Wait for the task to complete
    Console.Writeline(erCount.toString());
}

You may altogether remove the shared field and return the error count. That way you can avoid unnecessary synchronization.

public static int erCount = 9;
static void Main(string[] args)
{
    var task = Task.Factory.StartNew(() => 
    { 
        int localErrorCount =0;
        ...do some task
        if(errorfound)
            localErrorCount++;
       return localErrorCount;
    });
    int errors = task.Result;//Wait for the task to complete and get the error count
    erCount += errors;
    Console.Writeline(erCount.toString());
}

Answer 2

You could use Interlocked.Increment() :

public int erCount = 9;
static void Main(string[] args){
    var task = Task.Factory.StartNew(() =>{ 
        ...do some task
        if(errorfound)
            Interlocked.Increment(ref erCount);
    });

    task.Wait(); // Wait for the task to complete before showing the error count
    Console.Writeline(erCount.toString());
}

Answer 3

The reason its not incrementing is:

Console.Writeline(erCount.toString());

executes before the error count has been incremented.

Move that inside the task at the end, and it should work.

You probably need to have a read up on the Task parrallel library and how multithreading works.