Passing an object by REF inside a foreach loop

Its summer time in India and its hard to resist drowsiness in the afternoon specially when you had a heavy lunch. So this afternoon while I was trying to take a nap, no one was watching :P, a friend of mine pinged me on IM, and says “dude, can’t I pass an object as ref inside a foreach loop?”, well my first reaction was “of course you can!!! “ but then I realized that its an iterator  and I can’t modify an object I am iterating on.

I opened a new instance of Visual Studio and create a new console application. In this application created a new class named testref with just two fields, one string and another one an int. In the main method created a generic list of type testref and filled it with five testref object. Then tried to loop through it and pass the loop variable as ref in a function. He was right, C# compiler throws an error “Cannot pass ‘xxyzobj’ as a ref or out argument because it is a ‘foreach iteration variable’”. following snippet shows the initial set of code

 class Program

    {

        class testref

        {

            public string val { get; set; }

            public int a {get;set;}


            public testref(string s)

            {

                val = s;

                a = 0;

            }

        }


        static void Main(string[] args)

        {

            List<testref> testcol = new List<testref>();


            testcol.Add(new testref("One"));

            testcol.Add(new testref("two"));

            testcol.Add(new testref("three"));

            testcol.Add(new testref("four"));

            testcol.Add(new testref("five"));


            foreach (testref s in testcol)

            {            

               MethodWithRef(ref s);

            }


            Console.ReadLine();

            

        }


        static void MethodWithRef(ref testref str)

        {

            str.val = str.val + " not";

            str.a = (new Random()).Next();

        }


}
In above code snippet, line in yellow will give the compilation error. Since this is a C# complier restriction there are couple of workaround to this situation.

Have a temporary variable and then pass this variable as the ref parameter in the method: 

testref tempObj;

foreach (testref s in testcol)

{

    tempObj = s;

    MethodWithRef(ref tempObj);

}

Use List.ForEach() method to apply an action on all the objects in the list: 

// Inside the main method pass the function name 

// you want to apply on each object

testcol.ForEach(MethodWithoutRef);


//Method to be applied on all the objects

static void MethodWithoutRef(testref str)

{

   str.val = str.val + " not";

   str.a = (new Random()).Next();

}
So that was it.. problem was solved…
PS: If you have some more ways this can be solved, Please do share.
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Manoj
			

			
							

Credit Crisis: How it happened??

Well nowadays everyone says, its economic downturn these days.. World economy is going through troubled times.. World is under recession … so on n so forth.. All headlines related to this have one word in common . CREDIT CRISIS .. I always wondered how it all started… So while stumbling across the web found 2 videos giving a good visualization and answer to the big question … How It all started…? so thought of sharing these with all..

 

 

 

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2009: Top 5 April Fool gags

Every year 1st April brings lots of funny email circulating around asking you to do strange things to get strange results 😛 (of course a h1 styled “April Fool” message floating on your computer screen).

Google comes with some amazing stuff every year on this EVE (he he). I eagerly wait for this day to see what they are gonna tell the world they are introducing today. This year they wrote a blog entry about CADIE taking over the online search.

But this time I like the one gag by OPERA team for introducing the Intuitive Browsing using Face gestures. 

This year’s top 5 gags are posted here. I found each one of them very good.

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