Regex find all occurrences of a pattern in a string

Question

I have a problem finding all occurences of a pattern in a string.

Check this string :

string msg= "=?windows-1258?B?UkU6IFRyIDogUGxhbiBkZSBjb250aW51aXTpIGQnYWN0aXZpdOkgZGVz?= =?windows-1258?B?IHNlcnZldXJzIFdlYiBHb1ZveWFnZXN=?=";

I want to return the 2 occurrences (in order to later decode them):

=?windows-1258?B?UkU6IFRyIDogUGxhbiBkZSBjb250aW51aXTpIGQnYWN0aXZpdOkgZGVz?=

and

=?windows-1258?B?IHNlcnZldXJzIFdlYiBHb1ZveWFnZXN=?="

With the following regex code, it returns only 1 occurrence: the full string.

var charSetOccurences = new Regex(@"=\?.*\?B\?.*\?=", RegexOptions.IgnoreCase);
var charSetMatches = charSetOccurences.Matches(input);
foreach (Match match in charSetMatches)
{
    charSet = match.Groups[0].Value.Replace("=?", "").Replace("?B?", "").Replace("?b?", "");
}

Do you know what I'm missing?

Answer 1

When regexp parser sees the .* character sequence, it matches everything up to the end of the string and goes back, char by char, (greedy match). So, to avoid the problem, you can use a non-greedy match or explicitly define the characters that can appear at a string.

"=\?[a-zA-Z0-9?=-]*\?B\?[a-zA-Z0-9?=-]*\?="