[2.0] Regex - find a match NOT located between two chars

Let's say I have this line of text:

aaa c b aa b ax

and I want to match all strings of a's not located between matched b's so in this case the matches would be {aaa, a}

I'm trying this regular expression but it doesn't work:
(?<!b.*)a+(?!.*b)

I'm trying to tell it to match all strings of a's except "those preceded by a b and followed by a b."

What this expression really says is match all strings of a's except "those preceded by a b OR followed by a b."

aaa - followed by a b

aa - preceded and followed by a b

a - preceded by a b

I'm wondering if there's a way to specify both 'not preceded by' and 'not followed by'

Am I in the wrong place for Regular Expressions help?

I think it should be
(?<!b)a+(?!b)

Quote:

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Originally Posted by wild_bill

I think it should be
(?<!b)a+(?!b)

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Unfortunately, that won't work either. I probably didn't make it clear what I want to find. I want to find a's not located anywhere between matching b's, not just right in front of or right behind a 'b'.

Consider this input string:

Code:

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ab  a b    b    a    baaa

^ this 'a' should be found but won't since a 'b' directly follows it

    ^ this 'a' will be found even though it shouldn't since it is
    between two matching 'b' but isn't directly preceded or followed by a 'b'.

                ^ same as above

                      ^ only the last two 'a' will be found since the first 'a'
                      is followed by a 'b'.

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Code:

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                        string noBs = Regex.Replace("ab  a b    b    a    baaa","b.*?b","");
                        foreach (Match mt in Regex.Matches(noBs,"a+"))
                        {
                                Console.WriteLine(mt.Value);
                        }

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