Question

Anyone care to comment on whether we should be using “I” or “II” and “&” or “&&” in our LINQ Where() extensions / queries? Any difference with LINQ to SQL? The resulting expression tree is more than I can get my brain around on a Friday afternoon

Thanks,

static void Main(string[] args)
{
    var numbers = new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 9 };

    var q1 = numbers.Where(i => i == 1 | i == 2);
    var q2 = numbers.Where(i => i == 1 || i == 2);

    var q3 = numbers.Where(i => i == 1 & i < 3);
    var q4 = numbers.Where(i => i == 1 && i < 3);

    Write(q1);
    Write(q2);
    Write(q3);
    Write(q4);
}

static void Write<T>(IEnumerable<T> t)
{
    foreach (var i in t)
        Console.Write("{0} ", i);

    Console.WriteLine();
}


Results:

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Answer 1

You want || / &&.

Well, the single-pipe (| / &) is generally used for bitwise arithmetic, and (among other problems) may make the code base harder to understand; it’ll work in LINQ-to-Objects (since bitwise is still defined for bool), but without the usual short-circuiting. But if your data source is a database (i.e. there is an expression parser in the mix), you may find it explodes on you.

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OK; bitwise may have been misleading; but || and && remains the most logical and expected way of expressing your intent. My apologies for any confusion.