我想将字符串拆分为列表或数组。
输入：green,"yellow,green",white,orange,"blue,black"
拆分字符是逗号（,），但它必须忽略引号内的逗号。
输出应为：
感谢。
答案 0 :(得分：12)
实际上这很容易使用匹配：
string subjectString = @"green,""yellow,green"",white,orange,""blue,black""";
try
{
Regex regexObj = new Regex(@"(?<="")\b[a-z,]+\b(?="")|[a-z]+", RegexOptions.IgnoreCase);
Match matchResults = regexObj.Match(subjectString);
while (matchResults.Success)
{
Console.WriteLine("{0}", matchResults.Value);
// matched text: matchResults.Value
// match start: matchResults.Index
// match length: matchResults.Length
matchResults = matchResults.NextMatch();
}
输出：
green
yellow,green
white
orange
blue,black
说明：
@"
# Match either the regular expression below (attempting the next alternative only if this one fails)
(?<= # Assert that the regex below can be matched, with the match ending at this position (positive lookbehind)
"" # Match the character “""” literally
)
\b # Assert position at a word boundary
[a-z,] # Match a single character present in the list below
# A character in the range between “a” and “z”
# The character “,”
+ # Between one and unlimited times, as many times as possible, giving back as needed (greedy)
\b # Assert position at a word boundary
(?= # Assert that the regex below can be matched, starting at this position (positive lookahead)
"" # Match the character “""” literally
)
| # Or match regular expression number 2 below (the entire match attempt fails if this one fails to match)
[a-z] # Match a single character in the range between “a” and “z”
+ # Between one and unlimited times, as many times as possible, giving back as needed (greedy)
"
答案 1 :(得分：5)
你所拥有的是一种不规范的语言。换句话说，字符的含义取决于字符之前或之后的字符序列。顾名思义，正则表达式用于解析常规语言。
您需要的是Tokenizer和Parser，一个优秀的互联网搜索引擎应该引导您进行示例。事实上，因为令牌只是字符，你可能甚至不需要Tokenizer。
虽然你可以使用正则表达式来完成这个简单的情况，但它可能非常慢。如果引号没有平衡，它也可能导致问题，因为正则表达式不会检测到这个错误，而解析器会这样。
如果您要导入CSV文件，您可能需要查看Microsoft.VisualBasic.FileIO.TextFieldParser类（只需在C＃项目中添加对Microsoft.VisualBasic.dll的引用）即可解析CSV文件。
另一种方法是编写自己的state machine（例如下面的代码），尽管这仍然无法解决值中间的引用问题：
using System;
using System.Text;
namespace Example
{
class Program
{
static void Main(string[] args)
{
string subjectString = @"green,""yellow,green"",white,orange,""blue,black""";
bool inQuote = false;
StringBuilder currentResult = new StringBuilder();
foreach (char c in subjectString)
{
switch (c)
{
case '\"':
inQuote = !inQuote;
break;
case ',':
if (inQuote)
{
currentResult.Append(c);
}
else
{
Console.WriteLine(currentResult);
currentResult.Clear();
}
break;
default:
currentResult.Append(c);
break;
}
}
if (inQuote)
{
throw new FormatException("Input string does not have balanced Quote Characters");
}
Console.WriteLine(currentResult);
}
}
}
答案 2 :(得分：2)
有人会很快拿出一个用一个正则表达式来做到这一点的答案。我不是那么聪明，但为了平衡，这里有一个不完全使用正则表达式的建议。基于一句古老的格言，当你尝试用正则表达式解决问题时，你就会遇到两个问题。 ：）
就个人而言，由于缺乏正则表达式，我会做以下其中一项：
Replace以其他内容（即","）转义 引号内的任何逗号。然后，您可以对结果执行简单的string.Split()，并在使用之前对结果数组中的每个项目进行unescape。这太可惜了。部分是因为它处理了所有事情，部分是因为它也使用了正则表达式。 Boooo！如果编写良好，非正则表达式选项很有可能表现得更好，因为正则它们在内部扫描字符串寻找模式时可能有点贵。
真的，我只想指出你不必使用正则表达式。 ：）
这是我第二个建议的相当天真的实现。在我的电脑上，它很乐意在4.5秒内解析100万个15列字符串。
public class ManualParser : IParser
{
public IEnumerable<string> Parse(string line)
{
if (string.IsNullOrWhiteSpace(line)) return new List<string>();
line = line.Trim();
if (line.Contains(",") == false) return new[] { line.Trim('"') };
if (line.Contains("\"") == false) return line.Split(',').Select(c => c.Trim());
bool withinQuotes = false;
var builder = new List<string>();
var trimChars = new[] { ' ', '"' };
int left = 0;
int right = 0;
for (right = 0; right < line.Length; right++)
{
char c = line[right];
if (c == '"')
{
withinQuotes = !withinQuotes;
continue;
}
if (c == ',' && !withinQuotes)
{
builder.Add(line.Substring(left, right - left).Trim(trimChars));
right++; // Jump the comma
left = right;
}
}
builder.Add(line.Substring(left, right - left).Trim(trimChars));
return builder;
}
}
以下是一些单元测试：
[TestFixture]
public class ManualParserTests
{
[Test]
public void Parse_GivenStringWithNoQuotesAndNoCommas_ShouldReturnThatString()
{
// Arrange
var parser = new ManualParser();
// Act
string[] result = parser.Parse("This is my data").ToArray();
// Assert
Assert.AreEqual(1, result.Length, "Should only be one column returned");
Assert.AreEqual("This is my data", result[0], "Incorrect value is returned");
}
[Test]
public void Parse_GivenStringWithNoQuotesAndOneComma_ShouldReturnTwoColumns()
{
// Arrange
var parser = new ManualParser();
// Act
string[] result = parser.Parse("This is, my data").ToArray();
// Assert
Assert.AreEqual(2, result.Length, "Should be 2 columns returned");
Assert.AreEqual("This is", result[0], "First value is incorrect");
Assert.AreEqual("my data", result[1], "Second value is incorrect");
}
[Test]
public void Parse_GivenStringWithQuotesAndNoCommas_ShouldReturnColumnWithoutQuotes()
{
// Arrange
var parser = new ManualParser();
// Act
string[] result = parser.Parse("\"This is my data\"").ToArray();
// Assert
Assert.AreEqual(1, result.Length, "Should be 1 column returned");
Assert.AreEqual("This is my data", result[0], "Value is incorrect");
}
[Test]
public void Parse_GivenStringWithQuotesAndCommas_ShouldReturnColumnsWithoutQuotes()
{
// Arrange
var parser = new ManualParser();
// Act
string[] result = parser.Parse("\"This is\", my data").ToArray();
// Assert
Assert.AreEqual(2, result.Length, "Should be 2 columns returned");
Assert.AreEqual("This is", result[0], "First value is incorrect");
Assert.AreEqual("my data", result[1], "Second value is incorrect");
}
[Test]
public void Parse_GivenStringWithQuotesContainingCommasAndCommas_ShouldReturnColumnsWithoutQuotes()
{
// Arrange
var parser = new ManualParser();
// Act
string[] result = parser.Parse("\"This, is\", my data").ToArray();
// Assert
Assert.AreEqual(2, result.Length, "Should be 2 columns returned");
Assert.AreEqual("This, is", result[0], "First value is incorrect");
Assert.AreEqual("my data", result[1], "Second value is incorrect");
}
}
这是一个示例应用程序，我测试了吞吐量：
class Program
{
static void Main(string[] args)
{
RunTest();
}
private static void RunTest()
{
var parser = new ManualParser();
string csv = Properties.Resources.Csv;
var result = new StringBuilder();
var s = new Stopwatch();
for (int test = 0; test < 3; test++)
{
int lineCount = 0;
s.Start();
for (int i = 0; i < 1000000 / 50; i++)
{
foreach (var line in csv.Split(new[] { Environment.NewLine }, StringSplitOptions.None))
{
string cur = line + s.ElapsedTicks.ToString();
result.AppendLine(parser.Parse(cur).ToString());
lineCount++;
}
}
s.Stop();
Console.WriteLine("Completed {0} lines in {1}ms", lineCount, s.ElapsedMilliseconds);
s.Reset();
result = new StringBuilder();
}
}
}
答案 3 :(得分：2)
您尝试拆分的字符串格式似乎是标准CSV。使用CSV解析器可能更容易/更快。