C# 正则表达式拆分但如果拆分失败则包含空字符串
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【中文标题】C# 正则表达式拆分但如果拆分失败则包含空字符串【英文标题】：C# Regex Split but include empty string if fails to split 【发布时间】：2019-06-07 23:40:03 【问题描述】：我正在尝试将一个字符串拆分为一个字符串数组。 我当前的字符串看起来像这样，这都在一个字符串中。它还有换行符 (\r\n) 和空格。我在这里放了一个更好看的例子。
BFFPPB14 Dark Chocolate Dried Cherries 14 oz (397g)
INGREDIENTS: DARK CHOCOLATE (SUGAR, CHOCOLATE LIQUOR, COCOA BUTTER,
ANHYDROUS MILK FAT, SOYA LECITHIN, VANILLIN [AN ARTIFICIAL FLAVOR]), DRIED
TART CHERRIES (CHERRIES, SUGAR), GUM ARABIC, CONFECTIONER'S GLAZE.
CONTAINS: MILK, SOY
ALLERGEN INFORMATION: MAY CONTAIN TREE NUTS, PEANUTS, EGG AND
WHEAT.
01/11/2019
Description: Sweetened dried Montmorency cherries that are panned with dark chocolate.
Storage Conditions: Store at ambient temperatures with a humidity less than 50%.
Shelf Life: 9 months
Company Name
Item No.: 701804
Bulk: 415265
Supplier: Cherryland's Best
WARNING: CHERRIES MAY CONTAIN PITS
我的正则表达式看起来像这样
List<string> result = Regex.Split(text, @"INGREDIENTS: |CONTAINS: |ALLERGEN INFORMATION: |(\d1,2/\d1,2/\d2,4)|Description: |Storage Conditions: |Shelf Life: |Company Name|Item No.: |Bulk: |Supplier: |WARNING: ").ToList();
This is what result looks like
注意：第一个字符串是产品名称
有时我得到没有供应商或警告的字符串，如果没有找到该拆分值，我希望拆分具有空字符串。
前：
result[0] = "blabla"
result[1] = ""
result[2] = "blabla"
这样我就知道结果 1 在值 (INGREDIENTS: ) 上进行了拆分，我可以将其分配给某些东西
【问题讨论】：
【参考方案1】：如果您在大容量应用程序中使用正则表达式，可能会出现性能问题。以下是您可以使用的一种可能的正则表达式。解析产品线和“公司名称”行有点困难，因为不清楚产品代码是否有模式并且公司名称行没有像其他字段一样的“：”，所以正则表达式在这些方面有点“hacky”：
using System;
using System.Text.RegularExpressions;
using System.Linq;
namespace so20190113_01
class Program
static void Main(string[] args)
string text =
@"BFFPPB14 Dark Chocolate Dried Cherries 14 oz (397g)
INGREDIENTS: DARK CHOCOLATE (SUGAR, CHOCOLATE LIQUOR, COCOA BUTTER, ANHYDROUS MILK FAT, SOYA LECITHIN, VANILLIN [AN ARTIFICIAL FLAVOR]), DRIED TART CHERRIES (CHERRIES, SUGAR), GUM ARABIC, CONFECTIONER'S GLAZE.
CONTAINS: MILK, SOY
ALLERGEN INFORMATION: MAY CONTAIN TREE NUTS, PEANUTS, EGG AND WHEAT.
01/11/2019
Description: Sweetened dried Montmorency cherries that are panned with dark chocolate.
Storage Conditions: Store at ambient temperatures with a humidity less than 50%. Shelf Life: 9 months
Company Name
Item No.: 701804
Bulk: 415265
Supplier: Cherryland's Best
WARNING: CHERRIES MAY CONTAIN PITS";
string pat =
@"^\s*(?<product>\w+\s+\w+\s+\w*[^:]+)$
|^ingredients:\s*(?<ingredients>.*)$
|^contains:\s*(?<contains>.*)$
|^allergen\s+information:\s*(?<allergen>.*)$
|^(?<date>(\d1,2/\d1,2/\d2,4))$
|^description:\s*(?<description>.*)$
|^storage\sconditions:\s*(?<storage>.*)$
|^shelf\slife:\s*(?<shelf>.*)$
|^company\sname\s*(?<company>.*)$
|^item\sno\.:\s*(?<item>.*)$
|^bulk:\s*(?<bulk>.*)$
|^supplier:\s*(?<supplier>.*)$
|^warning:\s*(?<warning>.*)$
";
Regex r = new Regex(pat, RegexOptions.IgnoreCase | RegexOptions.IgnorePatternWhitespace | RegexOptions.Multiline);
// Match the regular expression pattern against a text string.
Match m = r.Match(text); // you might want to use the overload that supports a timeout value
Console.WriteLine("Start---");
while (m.Success)
foreach (Group g in m.Groups.Where(x => x.Success))
switch (g.Name)
case "product":
Console.WriteLine($"Product(g.Success): 'g.Value.Trim()'");
break;
case "ingredients":
Console.WriteLine($"Ingredients(g.Success): 'g.Value.Trim()'");
break;
// etc.
m = m.NextMatch();
Console.WriteLine("End---");
【讨论】：
【参考方案2】：我认为解析器是唯一的方法。最初，我尝试使用这个正则表达式：
^([\w \.]+?):([\s\S]+?)(?=((^[\w \.]+?):))
其中的关键组件是前瞻?=，它允许字符串匹配标签之间的所有文本。但是，它不适用于最终行项目，因为它不在另一个标签之前，而且我找不到在可能不存在的模式处停止匹配的正则表达式。如果存在该正则表达式，您可以在一行代码中完成所有操作：
KeyValuePair<string, string>[] kvs = null;
//one line of code if the look-ahead would also consider non-existent matches
kvs = Regex.Matches(text, @"^([\w \.]+?):([\s\S]+?)(?=((^[\w \.]+?):))", RegexOptions.Multiline)
.Cast<Match>()
.Select(x => new KeyValuePair<string, string>(x.Groups[1].Value, x.Groups[2].Value.Trim(' ', '\r', '\n', '\t')))
.ToArray();
这段代码做得很好。此外，该文档的格式不一致，因为Company Name 不在冒号之前。这是唯一可行的锚模式，因为各种线都被新线打断了。
KeyValuePair<string, string>[] kvs = null;
//Otherwise, you have to write a parser
//get all start indexes of labels
var matches = Regex.Matches(text, @"^.+?:", RegexOptions.Multiline).Cast<Match>().ToArray();
kvs = new KeyValuePair<string, string>[matches.Length];
KeyValuePair<string, string> GetKeyValuePair(Match match1, int match1EndIndex)
//get the label
var label = text.Substring(match1.Index, match1.Value.Length - 1);
//get the desc and trim white space
var descStart = match1.Index + match1.Value.Length + 1;
var desc = text
.Substring(descStart, match1EndIndex - descStart)
.Trim(' ', '\r', '\n', '\t');
return new KeyValuePair<string, string>(label, desc);
for (int i = 0; i < matches.Length - 1; i++)
kvs[i] = GetKeyValuePair(matches[i], matches[i + 1].Index);
kvs[kvs.Length - 1] = GetKeyValuePair(matches[matches.Length - 1], text.Length);
foreach (var kv in kvs)
Console.WriteLine($"kv.Key: kv.Value");
【讨论】：
【参考方案3】：所以如果你的要求是：
查找以特定单词开头的行使用 Linq
使用 StartsWith
代码
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
namespace ConsoleApp12
class Program
public static void Main(string[] args)
// test string
var str = @"BFFPPB10 Dark Chocolate Macadamia Nuts 11 oz (312g)\r\nINGREDIENTS: DARK CHOCOLATE (SUGAR, CHOCOLATE, COCOA BUTTER, \r\nANHYDROUS MILK FAT, SOY LECITHIN, VANILLA), MACADAMIA NUTS, SEA SALT.\r\nCONTAINS: MACADAMIA NUTS, MILK, SOY.\r\nALLERGEN INFORMATION: MAY CONTAIN OTHER TREE NUTS, PEANUTS, EGG AND\r\nWHEAT.\r\n01/11/2019\r\nDescription: Dry roasted, salted macadamias covered in dark chocolate.\r\nStorage Conditions: Store at ambient temperatures with a humidity less than 50%. \r\nShelf Life: 12 months\r\nBlain's Farm & Fleet\r\nItem No.: 701772\r\nBulk: 421172\r\nSupplier: Devon's\r\n";
// Keys
const string KEY_INGREDIENTS = "INGREDIENTS:";
const string KEY_CONTAINS = "CONTAINS:";
const string KEY_ALLERGEN_INFORMATION = "ALLERGEN INFORMATION:";
const string KEY_DESCRPTION = "Description:";
const string KEY_STORAGE_CONDITION = "Storage Conditions:";
const string KEY_SHELFLIFE = "Shelf Life:";
const string KEY_ITEM_NO = "Item No.:";
const string KEY_BULK = "Bulk:";
const string KEY_SUPPLIER = "Supplier:";
const string KEY_WARNING = "WARNING:";
const string KEY_YEAR_Regex = @"^\d1,2/\d1,2/\d4$";
const string KEY_AFTER_COMPANY_NAME = KEY_ITEM_NO;
// Helpers
var keys = new string[]
KEY_INGREDIENTS, KEY_CONTAINS, KEY_ALLERGEN_INFORMATION, KEY_DESCRPTION, KEY_STORAGE_CONDITION,
KEY_SHELFLIFE, KEY_ITEM_NO, KEY_BULK, KEY_SUPPLIER, KEY_WARNING ;
var lines = str.Split(new string[] @"\r\n" , StringSplitOptions.RemoveEmptyEntries);
void log(string key, string val)
Console.WriteLine($"key => val");
Console.WriteLine();
void removeLine(string line)
if (line != null) lines = lines.Where(w => w != line).ToArray();
// get Multi Line Item with key
string getMultiLine(string key)
var line = lines
.Select((linetxt, index) => new linetxt, index )
.Where(w => w.linetxt.StartsWith(key))
.FirstOrDefault();
if (line == null) return string.Empty;
var result = line.linetxt;
for (int i = line.index + 1; i < lines.Length; i++)
if (!keys.Any(a => lines[i].StartsWith(a)))
result += lines[i];
else
break;
return result;
// get single Line Item before spesic key if the Line is not a key
string getLinebefore(string the_after_key)
var the_after_line = lines
.Select((linetxt, index) => new linetxt, index )
.Where(w => w.linetxt.StartsWith(the_after_key))
.FirstOrDefault();
if (the_after_line == null) return string.Empty;
var the_before_line_text = lines[the_after_line.index - 1];
//not a key
if (!keys.Any(a => the_before_line_text.StartsWith(a)))
return the_before_line_text;
else
return null;
// 1st get item without key
var itemName = lines.FirstOrDefault();
removeLine(itemName);
var year = lines.Where(w => Regex.Match(w, KEY_YEAR_Regex).Success).FirstOrDefault();
removeLine(year);
var companyName = getLinebefore(KEY_AFTER_COMPANY_NAME);
removeLine(companyName);
//2nd get item with Keys
var ingredients = getMultiLine(KEY_INGREDIENTS);
var contanins = getMultiLine(KEY_CONTAINS);
var allergenInfromation = getMultiLine(KEY_ALLERGEN_INFORMATION);
var description = getMultiLine(KEY_DESCRPTION);
var storageConditions = getMultiLine(KEY_STORAGE_CONDITION);
var shelfLife = getMultiLine(KEY_SHELFLIFE);
var itemNo = getMultiLine(KEY_ITEM_NO);
var bulk = getMultiLine(KEY_BULK);
var supplier = getMultiLine(KEY_SUPPLIER);
var warning = getMultiLine(KEY_WARNING);
// 3rd log
log("ItemName", itemName);
log("Ingredients", ingredients);
log("contanins", contanins);
log("Allergen Infromation", allergenInfromation);
log("Year", year);
log("Description", description);
log("Storage Conditions", storageConditions);
log("Shelf Life", shelfLife);
log("CompanyName", companyName);
log("Item No", itemNo);
log("Bulk", bulk);
log("Supplier", supplier);
log("warning", warning);
Console.ReadLine();
会输出
ItemName => BFFPPB10 黑巧克力澳洲坚果 11 盎司（312 克）
成分 => 成分：黑巧克力（糖、巧克力、可可 黄油、无水乳脂、大豆卵磷脂、香草）、澳洲坚果、 海盐。
contanins => 包含：澳洲坚果、牛奶、大豆。
过敏原信息 => 过敏原信息：可能包含其他树 坚果、花生、鸡蛋和小麦。
年份 => 2019 年 1 月 11 日
描述 => 描述：干烤的盐渍澳洲坚果 黑巧克力。
储存条件 => 储存条件：常温储存 湿度小于 50% 的温度。
保质期 => 保质期：12 个月
CompanyName => Blain's Farm & Fleet
货号 => 货号：701772
批量 => 批量：421172
供应商 => 供应商：Devon's
警告 =>
【讨论】：
对不起。但这就是字符串的实际样子 "BFFPPB10 黑巧克力澳洲坚果 11 盎司（312 克）\r\n成分：黑巧克力（糖、巧克力、可可脂、\r\n无水乳脂、大豆卵磷脂、香草）、澳洲坚果、海盐。\r\n含有：澳洲坚果、牛奶、大豆。\r\n过敏原信息：可能含有其他坚果、花生、鸡蛋和\r\n小麦。\r\n01/11/2019\r\n描述：干用黑巧克力包裹的烤盐渍澳洲坚果。\r\n储存条件：在环境温度下储存，湿度低于 50%。\r\n保质期：12 个月\r\nBlain's Farm & Fleet\r\n货号：701772 \r\n散装：421172\r\n供应商：Devon's\r\n" 所以如果某个类别的字符串真的很长，它就会有新的行。而且您不能真正将其拆分为新行 是的，但是无水乳脂肪、大豆卵磷脂、香草）、澳洲坚果、海盐。是成分的一部分 非常感谢，这为我节省了很多时间。以上是关于C# 正则表达式拆分但如果拆分失败则包含空字符串的主要内容，如果未能解决你的问题，请参考以下文章