C#正則Groups高級使用方法

正則表達式號稱開發者得瑞士軍刀，使用好正則表達式尤其重要。

拆分多個正則：

 public static string[] SplitByManyRegex(string text, string[] subRegexStrings)
        {
            string allRegexString = "^(?<mySubGroup0>.*?)";
            for (int i = 0; i < subRegexStrings.Length; i++)
            {
                allRegexString += "(?<mySubGroup" + (i + 1) + ">" + subRegexStrings[i] + ".*?)";
            }
            allRegexString += "$";

            Regex subRegex = new Regex(allRegexString, RegexOptions.Singleline | RegexOptions.IgnoreCase);
            MatchCollection mc = subRegex.Matches(text);
            if (mc.Count <= 0)
            {
                return new string[] { text };
            }

            List<int> positions = new List<int>();
            for (int m = 0; m < subRegexStrings.Length + 1; m++)
            {
                positions.Add(mc[0].Groups["mySubGroup" + m].Index);
            }

            List<string> result = new List<string>();

            for (int i = 0; i < positions.Count; i++)
            {
                int nextPos = 0;
                if (i < positions.Count - 1) nextPos = positions[i + 1];
                else nextPos = text.Length;
                result.Add(text.Substring(positions[i], nextPos - positions[i]));
            }
            return result.ToArray();
        }

　　調用：

string[] tags = { "【答案】", "【解析】" };

　　拆分單個正則：

 public static string[] SplitByRegex(string text, string subRegexString)
        {
            Regex subRegex = new Regex(subRegexString, RegexOptions.Singleline | RegexOptions.IgnoreCase);
            MatchCollection mc = subRegex.Matches(text);
            if (mc.Count <= 0)
            {
                return new string[] { text };
            }

            List<int> positions = new List<int>();
            for (int m = 0; m < mc.Count; m++)
            {
                positions.Add(mc[m].Index);
            }

            List<string> result = new List<string>();
            result.Add(text.Substring(0, positions[0]));

            for (int i = 0; i < positions.Count; i++)
            {
                int nextPos = 0;
                if (i < mc.Count - 1) nextPos = positions[i + 1];
                else nextPos = text.Length;
                result.Add(text.Substring(positions[i], nextPos - positions[i]));
            }

            return result.ToArray();
        }

　　不反回第一條：

public static string[] SplitByRegexNoFirtPart(string text, string subRegexString)
        {
            string[] ary = SplitByRegex(text, subRegexString);
            return TrimFirstElementOfArray(ary);
        }

 private static string[] TrimFirstElementOfArray(string[] ary)
        {
            if (ary == null || ary.Length == 0) return new string[0];
            string[] result = new string[ary.Length - 1];
            for (int i = 1; i < ary.Length; i++) result[i - 1] = ary[i];
            return result;
        }

　　拆分如：(A(B(C?)?)?)

  public static string[] SplitByManyRegex_MayLess(string text, string[] subRegexStrings)
        {
            string allRegexString = "^(?<mySubGroup0>.*?)";

            for (int i = 0; i < subRegexStrings.Length; i++)
            {
                allRegexString += "((?<mySubGroup" + (i + 1) + ">" + subRegexStrings[i] + ".*?)";
            }
            for (int i = subRegexStrings.Length-1; i >=0 ; i--)
            {
                allRegexString += "?)";
            }

            allRegexString += "$";

            Regex subRegex = new Regex(allRegexString, RegexOptions.Singleline | RegexOptions.IgnoreCase);
            MatchCollection mc = subRegex.Matches(text);
            if (mc.Count <= 0)
            {
                return new string[] { text };
            }

            List<int> positions = new List<int>();
            for (int m = 0; m < subRegexStrings.Length + 1; m++)
            {
                if (mc[0].Groups["mySubGroup" + m].Success)
                {
                    positions.Add(mc[0].Groups["mySubGroup" + m].Index);
                }
            }

            List<string> result = new List<string>();

            for (int i = 0; i < positions.Count; i++)
            {
                int nextPos = 0;
                if (i < positions.Count - 1) nextPos = positions[i + 1];
                else nextPos = text.Length;
                result.Add(text.Substring(positions[i], nextPos - positions[i]));
            }
            return result.ToArray();
        }

　　可以任意順序，任意個數：

  public static string[] SplitByManyRegex_AnyOrder(string text, string[] subRegexStrings, bool resultChangeOrder = true )
        {
            if(string.IsNullOrEmpty(text) || subRegexStrings==null || subRegexStrings.Length == 0)
            {
                return new string[] { text };
            }

            string allReg = "(" + string.Join("|", subRegexStrings) + ")";
            string[] result = SplitByRegex(text, allReg);

            if (!resultChangeOrder) return result;
 
            string[] ordered = new string[subRegexStrings.Length+1];
            ordered[0] = result[0];
            for(int i=1; i<result.Length; i++)
            {
                //將某部分放到對應的正則順序
                for(int k=0; k< subRegexStrings.Length; k++)
                {
                    if(Regex.Match( result[i], subRegexStrings[k]).Success)
                    {
                        ordered[k+1] = result[i]; 
                    }
                }
                //如果某個沒有找到則保持為null
            }
            return ordered;
        }

　　用正則表達式替換文本中的內容：

 public static string TranformHandAnswer(string html)
        {
            string strReg = "(?<hand>(<handanswer>(.*?)</handanswer>))"; //正則表達式
            Regex regex = new Regex(strReg, RegexOptions.Singleline | RegexOptions.IgnoreCase);

            int _subjectOrderNum = subjectOrderNum;  //TODO: Lambda不允許ref變量，這里臨時這樣用
            html = regex.Replace(html, (Match match) =>
            {
                string handContent = match.Groups["hand"].Value;
                string result = “替換得文本”

                return result;
            });

            return html;
        }

　　有以上幾個輔助類，在難得正則拆分都能搞定。