使用正則表達式替換時尋找未轉義的字符

Question

我有一個要求，基本上是這樣的。如果我有一串文字，如

"There once was an 'ugly' duckling but it could 
never have been \'Scarlett\' Johansen" 

然後我想匹配尚未轉義的引號。這些將是'醜陋'周圍的那些，而不是圍繞'思嘉'的那些。

我已經花了很長時間在這個使用一個小小的C＃控制檯應用程序來測試的東西，並提出了以下解決方案。

private static void RegexFunAndGames() { 

    string result; 
    string sampleText = @"Mr. Grant and Ms. Kelly starred in the film \'To Catch A Thief' but not in 'Stardust' because they'd stopped acting by then"; 
    string rePattern = @"\\'"; 
    string replaceWith = "'"; 

    Console.WriteLine(sampleText); 

    Regex regEx = new Regex(rePattern); 
    result = regEx.Replace(sampleText, replaceWith); 

    result = result.Replace("'", @"\'"); 

    Console.WriteLine(result); 
} 

基本上我所做的是兩個步驟的過程中找到那些已經逃過的角色，撤消然後再做一切。這聽起來有點笨拙，我覺得可能有更好的辦法。

測試信息

我有兩個真正的好答案，所以我認爲這值得運行一個測試，看看它運行更好。我有這兩個功能：

private static string RegexReplace(string sampleText) { 
     Regex regEx = new Regex("(?<!\\\\)'"); 
     return regEx.Replace(sampleText, "\\'");   
    } 

    private static string ReplaceTest(string sampleText) { 
     return sampleText.Replace(@"\'", "'").Replace("'", @"\'"); 
    } 

而且我在一個控制檯應用程序調用它們在通過Main方法：

static void Main(string[] args) { 

     string sampleText = @"Mr. Grant and Ms. Kelly starred in the film \'To Catch A Thief' but not in 'Stardust' because they'd stopped acting by then."; 
     string testReplace = string.Empty; 
     System.Diagnostics.Stopwatch sw = new System.Diagnostics.Stopwatch(); 

     sw.Start(); 
     for (int i = 1000000; i > 0; i--) { 
      testReplace = ReplaceTest(sampleText); 
     } 

     sw.Stop(); 
     Console.WriteLine("This method took '" + sw.ElapsedMilliseconds.ToString() + "'"); 

     sw.Reset(); 
     sw.Start(); 
     for (int i = 1000000; i > 0; i--) { 
      testReplace = RegexReplace(sampleText); 
     } 

     sw.Stop(); 
     Console.WriteLine("This method took '" + sw.ElapsedMilliseconds.ToString() + "'"); 
} 

的方法ReplaceTest需要2068毫秒。 RegexReplace方法需要9372毫秒。我已經跑了幾次這個測試，並且ReplaceTest總是出來最快。

Answer 1

您可以使用負回顧後以確保報價是不轉義：表達低於

(?<!\\)' 

除非它立即被一個斜線相匹配的單引號。

請注意，進入字符串常量的斜槓必須加倍。

var sampleText = @"Mr. Grant and Ms. Kelly starred in the film \'To Catch A Thief' but not in 'Stardust' because they'd stopped acting by then"; 
var regEx = new Regex("(?<!\\\\)'"); 
var result = regEx.Replace(sampleText, "\\'"); 
Console.WriteLine(result); 

上面打印

Mr. Grant and Ms. Kelly starred in the film \'To Catch A Thief\' but not in \'Stardust\' because they\'d stopped acting by then 

Link to ideone.

Answer 2

你可以使用

string rePattern = @"[\\'|\']"; 

相反

Answer 3

我覺得很奇怪，爲什麼你正在使用正則表達式來做到這一點爲什麼不簡單地使用：

string result = sampleText.Replace(@"\'", "'").Replace("'", @"\'"); 

這將逃脫所有未轉義的'。

它將首先使所有轉義的'（單引號）未轉義，然後轉義all。

那麼，如果RegEx is the requirement，你會接受正確的解決方案，因爲你已經告訴。