Limit the number of parallel threads in C#

Question

I am writing a C# program to generate and upload a half million files via FTP. I want to process 4 files in parallel since the machine have 4 cores and the file generating takes much longer time. Is it possible to convert the following Powershell example to C#? Or is there any better framework such as Actor framework in C# (like F# MailboxProcessor)?

Powershell example

$maxConcurrentJobs = 3;

# Read the input and queue it up
$jobInput = get-content .\input.txt
$queue = [System.Collections.Queue]::Synchronized( (New-Object System.Collections.Queue) )
foreach($item in $jobInput)
{
    $queue.Enqueue($item)
}

# Function that pops input off the queue and starts a job with it
function RunJobFromQueue
{
    if( $queue.Count -gt 0)
    {
        $j = Start-Job -ScriptBlock {param($x); Get-WinEvent -LogName $x} -ArgumentList $queue.Dequeue()
        Register-ObjectEvent -InputObject $j -EventName StateChanged -Action { RunJobFromQueue; Unregister-Event $eventsubscriber.SourceIdentifier; Remove-Job $eventsubscriber.SourceIdentifier } | Out-Null
    }
}

# Start up to the max number of concurrent jobs
# Each job will take care of running the rest
for( $i = 0; $i -lt $maxConcurrentJobs; $i++ )
{
    RunJobFromQueue
}

Update:
The connection to remote FTP server can be slow so I want to limit the FTP uploading processing.

Answer 1

Assuming you're building this with the TPL, you can set the ParallelOptions.MaxDegreesOfParallelism to whatever you want it to be.

Parallel.For for a code example.

Answer 2

Task Parallel Library is your friend here. See this link which describes what's available to you. Basically framework 4 comes with it which optimises these essentially background thread pooled threads to the number of processors on the running machine.

Perhaps something along the lines of:

ParallelOptions options = new ParallelOptions();

options.MaxDegreeOfParallelism = 4;

Then in your loop something like:

Parallel.Invoke(options,
 () => new WebClient().Upload("http://www.linqpad.net", "lp.html"),
 () => new WebClient().Upload("http://www.jaoo.dk", "jaoo.html"));

Answer 3

If you are using .Net 4.0 you can use the Parallel library

Supposing you're iterating throug the half million of files you can "parallel" the iteration using a Parallel Foreach for instance or you can have a look to PLinq Here a comparison between the two