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.Net Implicit Conversion Rules

What are general guidelines for when a custom implicit conversion can, should, or should not be defined?

I mean things like, for example, "an implicit conversion should never lose information," "an implicit conversion should never throw exceptions," or "an implicit conversion should never create new objects." I am sure that the first one is correct, the third one is not (or we could ever have an implicit conversion to structures), and I do not know about the second.

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4 answers

The first is not as simple as you might expect. Here is an example:

using System;

class Test
{
    static void Main()
    {
        long firstLong = long.MaxValue - 2;
        long secondLong = firstLong - 1;

        double firstDouble = firstLong;
        double secondDouble = secondLong;

        // Prints False as expected
        Console.WriteLine(firstLong == secondLong);

        // Prints True!
        Console.WriteLine(firstDouble == secondDouble);        
    }
}

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The cross-border incident that made me ask this question is a violation of the second. Namely, I have the Lazy <T> class (not all?) And began to wonder if I should not provide an implicit conversion to T. My instinct is to say yes, and the current version is that, but I'm not too sure.

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