C# Replace替换的具体使用

// 作用：
// 将实例中出现的所有指定 Unicode 字符都替换为另一个指定的 Unicode 字符。
// 语法：
public string Replace (char oldChar, char newChar);

String str = "1 2 3 4 5 6 7 8 9";
Console.WriteLine($"Original string: {str}");
Console.WriteLine($"CSV string:      {str.Replace(' ', ',')}");
// 输出结果:
// Original string: "1 2 3 4 5 6 7 8 9"
// CSV string:      "1,2,3,4,5,6,7,8,9"

// 给 Char 类型的变量赋值可以通过多重方式，如下：
var chars = new[]
{
    'j',        //字符文本
    '\u006A',   //Unicode 转义序列，它是 \u 后跟字符代码的十六进制表示形式（四个符号）
    '\x006A',   //十六进制转义序列，它是 \x 后跟字符代码的十六进制表示形式
    (char)106,  //将字符代码的值转换为相应的 char 值
};
Console.WriteLine(string.Join(" ", chars));
// 输出的值相同: j j j j

// 作用：
// 实例中出现的所有指定字符串都替换为另一个指定的字符串
// 语法：
public string Replace (char oldString, char newString);

// 目的：将错误的单词更正
string errString = "This docment uses 3 other docments to docment the docmentation";
Console.WriteLine($"The original string is:{Environment.NewLine}'{errString}'{Environment.NewLine}");
// 正确的拼写应该为 "document"
string correctString = errString.Replace("docment", "document");
Console.WriteLine($"After correcting the string, the result is:{Environment.NewLine}'{correctString}'");
// 输出结果：
// The original string is:
// 'This docment uses 3 other docments to docment the docmentation'
//
// After correcting the string, the result is:
// 'This document uses 3 other documents to document the documentation'
//

// 可进行连续多次替换操作
String s = "aaa";
Console.WriteLine($"The initial string: '{s}'");
s = s.Replace("a", "b").Replace("b", "c").Replace("c", "d");
Console.WriteLine($"The final string: '{s}'");
// 如果 newString 为 null，则将 oldString 的匹配项全部删掉
s = s.Replace("dd", null);
Console.WriteLine($"The new string: '{s}'");

// 输出结果：
//The initial string: 'aaa'
//The final string: 'ddd'
//The new string: 'd'

public string Replace(string oldValue, string? newValue, StringComparison comparisonType)
{
	switch (comparisonType)
	{
		case StringComparison.CurrentCulture:
		case StringComparison.CurrentCultureIgnoreCase:
			return ReplaceCore(oldValue, newValue, CultureInfo.CurrentCulture.CompareInfo, 
                               GetCaseCompareOfComparisonCulture(comparisonType));
		case StringComparison.InvariantCulture:
		case StringComparison.InvariantCultureIgnoreCase:
			return ReplaceCore(oldValue, newValue, CompareInfo.Invariant, 
                               GetCaseCompareOfComparisonCulture(comparisonType));
		case StringComparison.Ordinal:
			return Replace(oldValue, newValue);
		case StringComparison.OrdinalIgnoreCase:
			return ReplaceCore(oldValue, newValue, CompareInfo.Invariant, CompareOptions.OrdinalIgnoreCase);
		default:
			throw new ArgumentException(SR.NotSupported_StringComparison, "comparisonType");
	}
}

// 以下示例为三种语言（"zh-CN", "th-TH", "tr-TR"）不同枚举值的测试代码和输出结果：
String[] cultureNames = { "zh-CN", "th-TH", "tr-TR" }; // 中国 泰国 土耳其
String[] strings1 = { "a", "i", "case", };
String[] strings2 = { "a-", "\u0130", "Case" };
StringComparison[] comparisons = (StringComparison[])Enum.GetValues(typeof(StringComparison));
foreach (var cultureName in cultureNames)
{
    Thread.CurrentThread.CurrentCulture = CultureInfo.CreateSpecificCulture(cultureName);
    Console.WriteLine("Current Culture: {0}", CultureInfo.CurrentCulture.Name);
    for (int ctr = 0; ctr <= strings1.GetUpperBound(0); ctr++)
    {
        foreach (var comparison in comparisons)
            Console.WriteLine("   {0} = {1} ({2}): {3}", strings1[ctr], strings2[ctr], comparison,
                              String.Equals(strings1[ctr], strings2[ctr], comparison));
        Console.WriteLine();
    }
    Console.WriteLine();
}

// 输出结果：
// Current Culture: zh-CN
//    a = a- (CurrentCulture): False //-----注意------
//    a = a- (CurrentCultureIgnoreCase): False //-----注意------
//    a = a- (InvariantCulture): False
//    a = a- (InvariantCultureIgnoreCase): False
//    a = a- (Ordinal): False
//    a = a- (OrdinalIgnoreCase): False
// 
//    i = İ (CurrentCulture): False
//    i = İ (CurrentCultureIgnoreCase): False //-----注意------
//    i = İ (InvariantCulture): False
//    i = İ (InvariantCultureIgnoreCase): False
//    i = İ (Ordinal): False
//    i = İ (OrdinalIgnoreCase): False
// 
//    case = Case (CurrentCulture): False
//    case = Case (CurrentCultureIgnoreCase): True
//    case = Case (InvariantCulture): False
//    case = Case (InvariantCultureIgnoreCase): True
//    case = Case (Ordinal): False
//    case = Case (OrdinalIgnoreCase): True
// 
// 
// Current Culture: th-TH
//    a = a- (CurrentCulture): True //-----注意------
//    a = a- (CurrentCultureIgnoreCase): True //-----注意------
//    a = a- (InvariantCulture): False
//    a = a- (InvariantCultureIgnoreCase): False
//    a = a- (Ordinal): False
//    a = a- (OrdinalIgnoreCase): False
// 
//    i = İ (CurrentCulture): False
//    i = İ (CurrentCultureIgnoreCase): False
//    i = İ (InvariantCulture): False
//    i = İ (InvariantCultureIgnoreCase): False
//    i = İ (Ordinal): False
//    i = İ (OrdinalIgnoreCase): False
// 
//    case = Case (CurrentCulture): False
//    case = Case (CurrentCultureIgnoreCase): True
//    case = Case (InvariantCulture): False
//    case = Case (InvariantCultureIgnoreCase): True
//    case = Case (Ordinal): False
//    case = Case (OrdinalIgnoreCase): True
// 
// 
// Current Culture: tr-TR
//    a = a- (CurrentCulture): False
//    a = a- (CurrentCultureIgnoreCase): False
//    a = a- (InvariantCulture): False
//    a = a- (InvariantCultureIgnoreCase): False
//    a = a- (Ordinal): False
//    a = a- (OrdinalIgnoreCase): False
// 
//    i = İ (CurrentCulture): False
//    i = İ (CurrentCultureIgnoreCase): True //-----注意------
//    i = İ (InvariantCulture): False
//    i = İ (InvariantCultureIgnoreCase): False
//    i = İ (Ordinal): False
//    i = İ (OrdinalIgnoreCase): False
// 
//    case = Case (CurrentCulture): False
//    case = Case (CurrentCultureIgnoreCase): True
//    case = Case (InvariantCulture): False
//    case = Case (InvariantCultureIgnoreCase): True
//    case = Case (Ordinal): False
//    case = Case (OrdinalIgnoreCase): True

public string Replace(string oldValue, string? newValue, bool ignoreCase, CultureInfo? culture)
{
	return ReplaceCore(oldValue, newValue, culture?.CompareInfo, ignoreCase ? CompareOptions.IgnoreCase : CompareOptions.None);
}
private string ReplaceCore(string oldValue, string newValue, CompareInfo ci, CompareOptions options)
{
	if ((object)oldValue == null)
	{
		throw new ArgumentNullException("oldValue");
	}
	if (oldValue.Length == 0)
	{
		throw new ArgumentException(SR.Argument_StringZeroLength, "oldValue");
	}
	return ReplaceCore(this, oldValue.AsSpan(), newValue.AsSpan(), ci ?? CultureInfo.CurrentCulture.CompareInfo, options) ?? this;
}
private static string ReplaceCore(ReadOnlySpan<char> searchSpace, ReadOnlySpan<char> oldValue, ReadOnlySpan<char> newValue, CompareInfo compareInfo, CompareOptions options)
{
	Span<char> initialBuffer = stackalloc char[256];
	ValueStringBuilder valueStringBuilder = new ValueStringBuilder(initialBuffer);
	valueStringBuilder.EnsureCapacity(searchSpace.Length);
	bool flag = false;
	while (true)
	{
		int matchLength;
		int num = compareInfo.IndexOf(searchSpace, oldValue, options, out matchLength);
		if (num < 0 || matchLength == 0)
		{
			break;
		}
		valueStringBuilder.Append(searchSpace.Slice(0, num));
		valueStringBuilder.Append(newValue);
		searchSpace = searchSpace.Slice(num + matchLength);
		flag = true;
	}
	if (!flag)
	{
		valueStringBuilder.Dispose();
		return null;
	}
	valueStringBuilder.Append(searchSpace);
	return valueStringBuilder.ToString();
}

// 语法
public string Replace (string input, string replacement);

// 目的是将多余的空格去掉
string input = "This is   text with   far  too   much   white space.";
string pattern = "\\s+"; // \s：匹配任何空白字符；+：匹配一次或多次
string replacement = " ";
Regex rgx = new Regex(pattern); // 实例化时传入正则表达式
string result = rgx.Replace(input, replacement);
Console.WriteLine("Original String: {0}", input);
Console.WriteLine("Replacement String: {0}", result);
// 输出结果：
// Original String: This is   text with   far  too   much   white space.
// Replacement String: This is text with far too much white space.

// 语法：
public static string Replace (string input, string pattern, string replacement);

// 目的：将多余的空格去掉
string input = "This is   text with   far  too   much   white space.";
string pattern = "\\s+"; 
// 注：\s  匹配任何空白字符，包括空格、制表符、换页符等
// 注：+   重复一次或多次
string replacement = " "; // 将连续出现的多个空格，替换为一个
string result = Regex.Replace(input, pattern, replacement);
Console.WriteLine("Original String: {0}", input);
Console.WriteLine("Replacement String: {0}", result);
// 输出结果：
//Original String: This is text with   far too   much white space.
//Replacement String: This is text with far too much white space.

// 语法：
public string Replace (string input, string replacement, int count, int startat);

// 目的：添加双倍行距
string input = "Instantiating a New Type\n" +
    "Generally, there are two ways that an\n" +
    "instance of a class or structure can\n" +
    "be instantiated. ";
Console.WriteLine("原内容：");
Console.WriteLine(input);
// .：匹配除‘\n'之外的任何单个字符；*：匹配零次或多次
string pattern = "^.*$"; // ^.*$ 在这里就是匹配每一行中‘\n'前边的字符串
string replacement = "\n$&"; // 在匹配项前添加‘\n'；$&：代表匹配内容
Regex rgx = new Regex(pattern, RegexOptions.Multiline); // Multiline：多行模式，不仅仅在整个字符串的开头和结尾匹配
string result = string.Empty;
Match match = rgx.Match(input); // 判断能否匹配
if (match.Success)
    result = rgx.Replace(input, 
                         replacement,
                         -1, // >= 0 时，就是匹配具体次数，= -1 时就是不限制次数
                         match.Index + match.Length + 1 // 作用就是跳过第一个匹配项（第一行不做处理）
                         // 当第一次匹配时：Index=0，length=除了‘\n'之外的长度，最后再 +1 就是第一行全部的内容
                        );
Console.WriteLine("结果内容：");
Console.WriteLine(result);
// 输出结果：
// 原内容：
// Instantiating a New Type
// Generally, there are two ways that an
// instance of a class or structure can
// be instantiated.
// 结果内容：
// Instantiating a New Type
// 
// Generally, there are two ways that an
// 
// instance of a class or structure can
// 
// be instantiated.

public static string Replace (string input, string pattern, 
                              System.Text.RegularExpressions.MatchEvaluator evaluator, 
                              System.Text.RegularExpressions.RegexOptions options, 
                              TimeSpan matchTimeout);

// 目的：将输入的每个单词中的字母顺序随机打乱，再一起输出
static void Main(string[] args)
{
    string words = "letter alphabetical missing lack release " +
        "penchant slack acryllic laundry cease";
    string pattern = @"\w+  # Matches all the characters in a word.";
    MatchEvaluator evaluator = new MatchEvaluator(WordScrambler); // WordScrambler：回调函数
    Console.WriteLine("Original words:");
    Console.WriteLine(words);
    Console.WriteLine();
    try
    {
        Console.WriteLine("Scrambled words:");
        Console.WriteLine(Regex.Replace(words, pattern, evaluator,
                RegexOptions.IgnorePatternWhitespace, TimeSpan.FromSeconds(2)));
    }
    catch (RegexMatchTimeoutException)
    {
        Console.WriteLine("Word Scramble operation timed out.");
        Console.WriteLine("Returned words:");
    }
}
/// <summary>
/// 回调：对全部匹配项逐一进行操作
/// </summary>
/// <param name="match"></param>
/// <returns></returns>
public static string WordScrambler(Match match)
{
    int arraySize = match.Value.Length;
    double[] keys = new double[arraySize]; // 存放随机数
    char[] letters = new char[arraySize]; // 存放字母
    Random rnd = new Random();
    for (int ctr = 0; ctr < match.Value.Length; ctr++)
    {
        keys[ctr] = rnd.NextDouble(); // 生成随机数，用于重新排序
        letters[ctr] = match.Value[ctr]; // 将输入参单词数拆解为字母数组
    }
    Array.Sort(keys, letters, 0, arraySize, Comparer.Default); // 重新根据随机数大小排序
    return new String(letters);
}
// 输出结果：
// Original words:
// letter alphabetical missing lack release penchant slack acryllic laundry cease
// 
// Scrambled words:
// eltetr aeplbtaiaclh ignisms lkac elsaree nchetapn acksl lcyaricl udarnly casee

string input = "Instantiating Instantiating Instantiating Instantiating";
Console.WriteLine("----原内容----");
Console.WriteLine(input);
string result = input.Replace("tiating","*******");
Console.WriteLine("----结果内容----");
Console.WriteLine(result);
// ----原内容----
// Instantiating Instantiating Instantiating Instantiating
// ----结果内容----
// Instan******* Instan******* Instan******* Instan*******

string input = "Instantiating Instantiating Instantiating Instantiating";
Console.WriteLine("----原内容----");
Console.WriteLine(input);
Regex regex = new Regex("tiating");
string result = regex.Replace(input, "*******",1);
Console.WriteLine("----结果内容----");
Console.WriteLine(result);
// ----原内容----
// Instantiating Instantiating Instantiating Instantiating
// ----结果内容----
// Instan******* Instantiating Instantiating Instantiating

string input = "Instantiating Instantiating Instantiating Instantiating";
Console.WriteLine("----原内容----");
Console.WriteLine(input);
Match match = Regex.Match(input, "tiating",RegexOptions.RightToLeft);
string first = input.Substring(0, match.Index);
string last = input.Length == first.Length + match.Length ? "" : 
input.Substring(first.Length + match.Length,input.Length-(first.Length + match.Length));
string result = $"{first}*******{last}";
Console.WriteLine("----结果内容----");
Console.WriteLine(result);
// 两次测试结果：
// ----原内容----
// Instantiating Instantiating Instantiating Instantiating 345
// ----结果内容----
// Instantiating Instantiating Instantiating Instan******* 345
// ----原内容----
// Instantiating Instantiating Instantiating Instantiating
// ----结果内容----
// Instantiating Instantiating Instantiating Instan*******