.net ToString() format documentation

Question

I saw a code snippet the other day that converts a Boolean value to the corresponding \"Yes\"/\"No\" value:

CDbl(True).ToString(\"Yes;Yes;No\")

Answer 1

As @Joel Coehoorn and @tvanfosson said, it's using a custom numeric format string. The reason it works is that a boolean value is convertible to a double using the following (essentially):

public static double ToDouble(bool value)
{
    return (value ? ((double) 1) : ((double) 0));
}

So, if value is true, it returns 1 and if value is false it returns 0. At that point, the section mapping rules apply as described by @tvanfosson (and subsequently @Joel Coehoorn).