Michael's Coding Den: CodeSnippets

Updating UI with anonymous delegate

Wed, 01 Mar 2006 19:35:06 GMT

Williams gave a codesnippet of how to update UI from another thread with AD http://spaces.msn.com/staceyw/blog/cns!F4A38E96E598161E!652.entry?_c11_blogpart_blogpart=blogview&_c=blogpart#permalink

Interrupting Thread in robust way

Mon, 20 Feb 2006 12:03:53 GMT

using System;
using System.IO;
using System.Threading;

class App
{
    static volatile bool terminate = false;
    static void Main(string[] args)
    {
        Thread t = new Thread(new ThreadStart(Func));
        t.Start();
        Console.ReadLine();
        // set the flag to get the thread to come down cleanly
        terminate = true;
        if( !t.Join(2000) ) // if the thread has taken more than 2 seconds to terminate
        {
            // Wake the thread up
            t.Interrupt();
            // wait for it to terminate
            t.Join();
        }
    }
    static void Func()
    {
        // open some resource that requires clean up
        using(FileStream fs = File.OpenWrite(@"C:\foo.txt"))
        {
            // check the flag
            while(!terminate)
            {
                // use the resource
                fs.WriteByte(0);
                // oh dear, we aren't going to notice the flag for 10 seconds now
                Thread.Sleep(10000);
            }
        }
    }
}

Source: http://www.dotnetconsult.co.uk/weblog/PermaLink.aspx/4f52c396-1b0d-4419-8871-6ca6992460ca

Thread safe AND operation without locks

Mon, 20 Feb 2006 09:38:54 GMT

This snippet performs threadsafe AND operations, based on Interlocked calls.

public static class InterlockedEx
{
    public static Int32 And(ref Int32 target, Int32 with)
    {
        Int32 startVal, currentVal = target;
        // Don't access target in the loop except in an attempt
        // to change it because another thread may be touching it
        do
        {
            // Record this iteration's starting value
            startVal = currentVal;
            // Calculate the desired value (this example ANDs the bits)
            Int32 desiredVal = startVal & with;
            // NOTE: The thread could be pre-empted here
            // if (target == startVal) target = desiredVal;
            // Value prior to potential change is returned
            currentVal = Interlocked.CompareExchange(ref target, desiredVal, startVal);
            // If the starting value changed during this iteration, repeat
        }
        while (startVal != currentVal);
        // Return this iteration's starting value
        return currentVal;
    }
}

Source: http://msdn.microsoft.com/msdnmag/issues/05/10/ConcurrentAffairs/