删除字符并在数字之间选择的regex

下面是简单的正则表达式组用法:

using System;
using System.Text.RegularExpressions;

namespace RE {
    class TEST {
        static void Main(string[] args) {
            // Your string
            var str = "2018-12-26P18:07:05:07";
            // Regex to match 18 and 07 to 1 and second group.
            var re = new Regex(@"\d+-\d+-\d+[A-z](\d+):(\d+)");
            // Execute regex over string, and get our matched groups
            var match = re.Match(str);
            // Write the groups.
            Console.WriteLine(match.Groups[1].Value + match.Groups[2].Value);
        }
    }
}