C# Blooper №9: Annoying case statement fall-through rules.

Before reading any further, please read the disclaimer.

Overall, C# takes an approach which is far more friendly to novice programmers than its predecessors, C and C++ were. For example, in the case of switch statements, C# does not allow the old, error-prone style of C and C++ where you could simply fall through from one case statement to the following one; instead, at the end of each case statement C# requires either a break statement, or a goto statement to explicitly jump to another label. That's all very nice and dandy, except for one thing: C# requires a break or goto even at the last case statement of a switch statement!

namespace Test9
{
    class Test
    {
        void statement() { }

        void wtf_is_it_with_falling_through_the_last_case_label( int a )
        {
            switch( a )
            {
                case 42:
                    statement();
                    break;
                default:
                    statement();
                    break; //Need this 'break' or else: CS0163: Control cannot fall through from one case label ('default:') to another
            }
        }
    }
}

I mean, seriously, WTF?

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C# Blooper №8: No warnings for conditions that are always true/false

Before reading any further, please read the disclaimer.

The Microsoft C# compiler does not issue 'condition is always true' and 'condition is always false' warnings. Perhaps these warnings are not particularly meaningful in Java, which lacks conditional compilation directives, and therefore if( true ) and if( false ) are the only means of achieving conditional compilation; but in C#, which has special conditional compilation directives, conditions which are always true or always false are invariably so by mistake; therefore, these warnings would indeed be meaningful, and useful.

namespace Test8
{
    class Test
    {
        void statement() { }

        void test()
        {
            if( true ) //no warning about 'condition is always true'.
                statement();

            while( false ) //no warning about 'condition is always false', even though the compiler obviously knows what's going on, since the following warning is issued:
                statement(); //warning CS0162: Unreachable code detected 
        }
    } 
}

For more information see Why the Microsoft C# compiler lacks many useful warnings.

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C# Blooper №7: No warnings about unused private methods.

Before reading any further, please read the disclaimer.

If you have a private method which is never used, you will not be given a warning about it by the Microsoft C# compiler. This means that your app will likely get shipped with unnecessary chunks of code in it, some of them possibly containing string litterals that were never meant to make it out of the development environment, or even requiring libraries to be linked which were never meant to be required on the field.

namespace Test7
{
    class Test
    {
        private void unused() //no warning about unused private method.
        {
        }
    }
}

For more information see Why the Microsoft C# compiler lacks many useful warnings.

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C# Blooper №6: No warnings about unused parameters.

Before reading any further, please read the disclaimer.

One common mistake that programmers make is to forget to make use of a parameter to a method. This can lead to quite subtle bugs that are hard to track down and correct.

Now, other language compilers are kind enough to warn the programmer that a parameter is unused, and they also allow temporary suppression of the warning for the rare case when such lack of use is legitimate. But not so in Visual C#. If you forget to use a parameter in Visual C#, you will not know unless you run the "Code Analysis" tool on it.

namespace Test6
{
    class Test
    {
        void moo( int a ) //no warning about unused parameter 'a'.
        {
        }
    }
}

For more information see Why the Microsoft C# compiler lacks many useful warnings.

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Why the Microsoft C# compiler lacks many useful warnings

As my C# Bloopers series of articles shows, the Microsoft C# compiler fails to issue many useful warnings which one would reasonably expect from a decent compiler of any language, and which are in fact readily and lavishly issued by Java compilers.

After all these years that the Microsoft C# compiler has been maturing, one cannot help but postulate that there are alterior motives behind this continued state of misery with respect to warnings. For lo and behold, it just so happens that the "Ultimate" (most feature-packed and most outrageously expensive) edition of Microsoft Visual Studio contains a "Code Analysis" feature, which is capable of issuing hundreds of different types of warnings, ranging from the pedantic to the arcane, and including most, if not all, of the missing warnings that I am discussing here.

Now, besides the fact that the Code Analysis feature comes at a considerable additional cost, it is also very cumbersome to use on a frequent basis, since it has been built as a separate product feature, instead of having been integrated into the compiler. For one thing, it is very slow. Another thing is that it is very spammy: we are talking about multiple warnings for every single line of code here, most of which are useless, and the first thing you need to do about them is to turn them off. And there are several dozen warnings to turn off. 

This cumbersomeness makes the Code Analysis feature unsuitable for use in the instant builds which developers tend to perform every few minutes or so, and more suitable to use as a separate code-quality-assurance step to be performed once or twice during the entire development process of a product, or at best on nightly builds. Unfortunately, it is precisely on instant builds that the warnings I am talking about in these articles are most useful. Better yet, most of these warnings are useful in real-time, while typing the code, in the form of yellow curly underlines. For example, as a developer, I want to know that a parameter to a method I have just written goes unused before I even proceed to start coding the next method, because it most probably means that I forgot something or I did something wrong. This information is useful not tomorrow, not in a couple of months, but right now.

So, what has probably happened here is that the Microsoft C# compiler team was told by Microsoft's marketing department to intentionally cripple the C# compiler and make it less useful to all of us, by moving some of the functionality which rightfully belongs to it into some other module, so that their premium "Ultimate" product can have a raison d'être.

I bet you that Balmer is behind this.

C# Blooper №5: Lame/annoying variable scoping rules, Part 2

Before reading any further, please read the disclaimer.

In light of the previous blooper, this one is more of a confusing error message than an actual new blooper. What I am doing below is that I am declaring a field within a class, I am accessing that field from within a method, and further down within the same method I am declaring a new local variable with the same name as the field. Now, C# will not allow me to declare that local variable because it has the same name as the field, but that's not where I am receiving the error. Instead, the error is given when accessing the field. If you only read the first sentence of the error message, it does not make any sense at all. If you bother also reading the second sentence, it gives you a hint as to the real problem. Now, that's not very cool.

namespace Test5
    {
        public class Test
        {
            public int a;

            void foo()
            {
                for( int i = 0;  i < 10;  i++ )
                {
                    a = 10; //error CS0844: Cannot use local variable 'a' before it is declared. The declaration of the local variable hides the field 'Test5.Test.a'.
                }
                string a = "";
                Console.WriteLine( a );
            }
        }
    }

See also: C# Blooper №4: Lame/annoying variable scoping rules, Part 1
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How to get a raise

Once upon a time I was dissatisfied with my salary at my workplace, and I let it show. The boss, fearing that he was about to lose me, placed an ad in the newspaper for my exact job description. Since I was looking for a job, I saw the ad in the newspaper. What I did was to reply to that ad, sending my boss my resume, which of course included precisely those qualifications that the job required. The boss got the message.

C# Blooper №4: Lame/annoying variable scoping rules, Part 1

Before reading any further, please read the disclaimer.

A variable identifier is, of course, only visible within the scope in which it is declared. This includes nested (child) scopes, but it does not include enclosing (parent) scopes. In C# however, once a variable identifier has been used in a scope, its name is "poisoned", so it cannot be used in enclosing scopes. Take this example:

namespace Test4
{
    class Test
    {
        void test()
        {
            if( this != null )
            {
                object o;
                o = null;
                if( o == this )
                    return;
            }
            object o;  //error CS0136: A local variable named 'o' cannot be declared in this scope because it would give a different meaning to 'o', which is already used in a 'child' scope to denote something else
        }
    }
}

Well, I am sorry, but in the above case the new variable named 'o' would most definitely *not* give a different meaning to the 'o' which was used in the child scope. It would, if it had been declared before the 'if' statement, but it wasn't. Luckily, if this "feature" was to be removed from the language, it would not break any existing code. So, can we please have this fixed? Pretty please?

See also: C# Blooper №5: Lame/annoying variable scoping rules, Part 2

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How to copy multiple contacts from Outlook to Lync

It is kind of amazing how crippled the co-operation is between Microsoft Outlook and Microsoft Lync. (Note:  I am talking about Microsoft Office Professional Plus 2010, with Outlook version 14.0 32-bit and Lync 2010.) All I wanted to do was to copy contacts from the Outlook contacts list to the Lync contacts list. Never mind the fact that these two programs should be sharing the exact same contact list and I should not have to do anything of that sort; it sounds like a simple task, right?  Copy contacts from one program to another. These two programs belong to the same Office suite and are supposedly seamlessly integrated with each other. Well, seamlessly my @$$. You can copy single contacts from Lync to Outlook. But if you want to copy a contact from Outlook to Lync, or copy multiple contacts, then you are completely out of luck.  No-can-do, apparently.

Well, I found a trick to do it.  Here is how:

1. Select all the contacts within Outlook that you want to copy to Lync.
2. Hit "Send email", and a new email will be prepared, with all the selected contacts in the "To:" field.
3. Select all the contacts in the "To:" field.
4. Drag and drop the contacts from the "To:" field into a group (not contact) in Lync.
5. Discard the new email.

Voila!

If you know of a simpler way, please let me know.

Also, if you know of any way to do perform the incredibly advanced operation of... (drum roll please) PRINT YOUR OUTLOOK CONTACTS WITH PICTURES, (duh!) please let me know.

Cheers!

Scanning printed photos

I was looking around for advice on what settings are best for scanning printed photos and I was amazed by the number of answers floating around on the great interwebz which are misguided, or are technically correct but miss the point. So, here is my advice.

First of all, let us define the goal: For a home user to scan printed photos so as to retain as much as possible of the visual information contained in the print, within reasonable limits, and without wasting too much space.

The answer, in a nutshell:  Scan at 600dpi, save as 24-bit-color compressed PNG or compressed TIFF. Do not use any of the fancy options for noise reduction, color correction, contrast enhancement, etc that might be provided by your scanner. If you need to improve something, edit the scanned picture later using your favorite image processing software, but never touch the original scanned files: always work on a copy of the original.

If the nutshell is good enough for you, then off you go, and happy scanning.

If you are interested to know why, read on.

Please note that the way the goal was expressed, we do not have to take into consideration what we are planning to do with the pictures later. When you scan, scan for posterity. Scan so that you can later crop, rotate, retouch, print. etc. If the photos need to be communicated through a low-resolution medium such as the web, then you can later make scaled-down copies for that purpose. But at the time of scanning, the point is to not limit yourself on what you will be able to do later with the scanned photos.

The resolution of photo prints ranges between 150 and 300 dpi. When we scan at 600 dpi, we are doing twice the resolution of a photo print, (or better,) which is the theoretical maximum required so as to capture all the information that there is on the photo print. Every bit of it. Not an iota of information left out. Sure, some color fidelity will inevitably get lost, but that's a different ball game altogether. As far as resolution is concerned, anything above 600 dpi is a pure waste of space.

24 bits per pixel is also perfectly adequate to fully match the capacity of film to convey color. There will be some reduction in color fidelity stemming from the fact that the sRGB color space into which you will most likely be scanning will not necessarily (and in all likelihood never) exactly match the color space of the photo, but the loss in fidelity will be imperceptible, and the measures required to correct this problem are disproportionately painstaking, and outside the "within reasonable limits" requirement stated as the goal in the beginning of this article. Furthermore, when you are working with differences in quality that are not perceptible, it is very easy to make a mistake which reduces, rather than enhances, the fidelity of the digitization, even by an imperceptible amount, and you will never know. So, color is best left at 24 bits per pixel sRGB and never messed with.

Use compressed PNG or TIFF because these file formats offer LOSSLESS compression. Lossless compression means that 100% of the information in the image is retained. Not very close to 100%, not imperceptibly different from 100% but precisely 100%.  Time and again I hear about people who save their pictures in uncompressed TIFF format; obviously, they do not understand squat about compression. It really is not rocket science: there are two kinds of compression, lossy and lossless. Lossy compression (JPEG) achieves huge savings, at a slight (usually imperceptible) expense to quality. Lossless compression (PNG, TIFF) achieves great, but not huge savings, at NO expense to quality. Using no compression serves no purpose, and is just plain stupid. It just spreads your picture over more sectors on your hard drive, increasing the chance that it will one day be lost due to a sector going bad.

Since lossy compression usually represents an imperceptible loss of quality, we could be scanning into JPEG, but the problem here is that if we ever retouch the picture, and then save it again as JPEG, the lossy compression will be re-applied, thus compounding the loss of quality. Keep repeating this cycle, and at some point the deterioration will start becoming perceptible. That's why we always use lossless compression on originals and on working copies, and lossy compression when publishing.