var rePost = new Regex("POST\d+\s*?=\s*?\d+");
var reTest = new Regex("TEST\d+\s*?=\s*?\d+");

class Program
{
	static void Main(string[] args)
	{

		const string str = @"(TEST1 = 111 OR TEST1 = 222) AND (POST1 = 555)";
		var rePost = new Regex(@"POST\d+\s*?=\s*?(\d+)");
		var reTest = new Regex(@"TEST\d+\s*?=\s*?(\d+)");

		int i = -1;
		var dic = new Dictionary<string, string[]>();
		var postMatches = rePost.Matches(str);
		var testMatches = reTest.Matches(str);

		string[] posts = new string[postMatches.Count];
		string[] tests = new string[testMatches.Count];

		dic.Add("POST", posts);
		dic.Add("TEST", tests);

		foreach (Match match in postMatches)
		{
			dic["POST"].SetValue(match.Groups[1].Value, ++i);
		}
		i = -1;
		foreach (Match match in testMatches)
		{
			dic["TEST"].SetValue(match.Groups[1].Value, ++i);
		}

		foreach (var key in dic.Keys)
		{
			Console.WriteLine("Key: " + key);
			foreach (var value in dic[key])
			{
				Console.WriteLine("\t" + value);
			}
		}
	}
}

class Program
{
	static void Main(string[] args)
	{

		const string str = @"(TEST1 = 111 OR TEST1 = 222) AND (POST1 = 555)";
		var matches = Regex.Matches(str, @"(?'name'(TEST|POST))\d+\s*?=\s*?(?'number'\d+)");
		var dic = new Dictionary<string, List<string>>();

		dic.Add("POST", new List<string>());
		dic.Add("TEST", new List<string>());

		foreach (Match match in matches)
		{
			dic[match.Groups["name"].Value].Add(match.Groups["number"].Value);
		}

		foreach (var key in dic.Keys)
		{
			Console.WriteLine("Key: " + key);
			foreach (var value in dic[key])
			{
				Console.WriteLine("\t" + value);
			}
		}
	}
}

Regex.Matches(str, @"(?'name'(TEST|POST))\d+\s*?=\s*?(?'number'\d+)").Cast<Match>().ToList().ForEach(m => Console.WriteLine(m.Groups["name"].Value + "=" + m.Groups["number"].Value));

Regex.Matches(str, @"(?'name'(TEST|POST))\d+\s*?=\s*?(?'number'\d+)").
	Cast<Match>().GroupBy(m => m.Groups["name"].Value).
	ToList().
	ForEach(group =>
	{
		Console.WriteLine(group.Key);
		group.ToList().ForEach(g => Console.WriteLine("\t" + g.Groups["number"].Value));
	});