拥有String.Replace的方式只打“整个单词”

我需要一种方法来做到这一点：

"test, and test but not testing.  But yes to test".Replace("test", "text")

返回此：

"text, and text but not testing.  But yes to text"

基本上我想替换整个单词，而不是部分匹配。

注意：为此，我将不得不使用VB（SSRS 2008代码），但是C＃是我的常规语言，因此使用两种方法都可以。

正则表达式是最简单的方法：

string input = "test, and test but not testing.  But yes to test";
string pattern = @"\btest\b";
string replace = "text";
string result = Regex.Replace(input, pattern, replace);
Console.WriteLine(result);

模式的重要部分是\b元字符，它在单词边界上匹配。如果您需要不区分大小写，请使用RegexOptions.IgnoreCase：

Regex.Replace(input, pattern, replace, RegexOptions.IgnoreCase);

我创建了一个包装正则表达式的函数（请参见博客文章），由Ahmad Mageed建议

/// <summary>
/// Uses regex '\b' as suggested in /programming/6143642/way-to-have-string-replace-only-hit-whole-words
/// </summary>
/// <param name="original"></param>
/// <param name="wordToFind"></param>
/// <param name="replacement"></param>
/// <param name="regexOptions"></param>
/// <returns></returns>
static public string ReplaceWholeWord(this string original, string wordToFind, string replacement, RegexOptions regexOptions = RegexOptions.None)
{
    string pattern = String.Format(@"\b{0}\b", wordToFind);
    string ret=Regex.Replace(original, pattern, replacement, regexOptions);
    return ret;
}

正如Sga所说，正则表达式解决方案并不完美。而且我想也不是性能友好的。

这是我的贡献：

public static class StringExtendsionsMethods
{
    public static String ReplaceWholeWord ( this String s, String word, String bywhat )
    {
        char firstLetter = word[0];
        StringBuilder sb = new StringBuilder();
        bool previousWasLetterOrDigit = false;
        int i = 0;
        while ( i < s.Length - word.Length + 1 )
        {
            bool wordFound = false;
            char c = s[i];
            if ( c == firstLetter )
                if ( ! previousWasLetterOrDigit )
                    if ( s.Substring ( i, word.Length ).Equals ( word ) )
                    {
                        wordFound = true;
                        bool wholeWordFound = true;
                        if ( s.Length > i + word.Length )
                        {
                            if ( Char.IsLetterOrDigit ( s[i+word.Length] ) )
                                wholeWordFound = false;
                        }

                        if ( wholeWordFound )
                            sb.Append ( bywhat );
                        else
                            sb.Append ( word );

                        i += word.Length;
                    }

            if ( ! wordFound )
            {
                previousWasLetterOrDigit = Char.IsLetterOrDigit ( c );
                sb.Append ( c );
                i++;
            }
        }

        if ( s.Length - i > 0 )
            sb.Append ( s.Substring ( i ) );

        return sb.ToString ();
    }
}

...带有测试用例：

String a = "alpha is alpha";
Console.WriteLine ( a.ReplaceWholeWord ( "alpha", "alphonse" ) );
Console.WriteLine ( a.ReplaceWholeWord ( "alpha", "alf" ) );

a = "alphaisomega";
Console.WriteLine ( a.ReplaceWholeWord ( "alpha", "xxx" ) );

a = "aalpha is alphaa";
Console.WriteLine ( a.ReplaceWholeWord ( "alpha", "xxx" ) );

a = "alpha1/alpha2/alpha3";
Console.WriteLine ( a.ReplaceWholeWord ( "alpha", "xxx" ) );

a = "alpha/alpha/alpha";
Console.WriteLine ( a.ReplaceWholeWord ( "alpha", "alphonse" ) );

我只想添加关于此特定正则表达式模式的注释（用于接受的答案和ReplaceWholeWord函数中）。如果您要替换的单词不是一个单词，那是行不通的。

这里是一个测试案例：

using System;
using System.Text.RegularExpressions;
public class Test
{
    public static void Main()
    {
        string input = "doin' some replacement";
        string pattern = @"\bdoin'\b";
        string replace = "doing";
        string result = Regex.Replace(input, pattern, replace);
        Console.WriteLine(result);
    }
}

（可以尝试使用的代码：http : //ideone.com/2Nt0A）

特别是如果您要进行批处理翻译时（例如我在某些i18n工作中所做的），则必须考虑到这一点。

如果要定义什么字符组成一个单词，即“ _”和“ @”

您可以使用我的（vb.net）函数：

 Function Replace_Whole_Word(Input As String, Find As String, Replace As String)
      Dim Word_Chars As String = "ABCDEFGHIJKLMNOPQRSTUVWYXZabcdefghijklmnopqrstuvwyxz0123456789_@"
      Dim Word_Index As Integer = 0
      Do Until False
         Word_Index = Input.IndexOf(Find, Word_Index)
         If Word_Index < 0 Then Exit Do
         If Word_Index = 0 OrElse Word_Chars.Contains(Input(Word_Index - 1)) = False Then
            If Word_Index + Len(Find) = Input.Length OrElse Word_Chars.Contains(Input(Word_Index + Len(Find))) = False Then
               Input = Mid(Input, 1, Word_Index) & Replace & Mid(Input, Word_Index + Len(Find) + 1)
            End If
         End If
         Word_Index = Word_Index + 1
      Loop
      Return Input
   End Function

测试

Replace_Whole_Word("We need to replace words tonight. Not to_day and not too well to", "to", "xxx")

结果

"We need xxx replace words tonight. Not to_day and not too well xxx"

我不喜欢Regex，因为它运行缓慢。我的功能更快。

public static string ReplaceWholeWord(this string text, string word, string bywhat)
{
    static bool IsWordChar(char c) => char.IsLetterOrDigit(c) || c == '_';
    StringBuilder sb = null;
    int p = 0, j = 0;
    while (j < text.Length && (j = text.IndexOf(word, j, StringComparison.Ordinal)) >= 0)
        if ((j == 0 || !IsWordChar(text[j - 1])) &&
            (j + word.Length == text.Length || !IsWordChar(text[j + word.Length])))
        {
            sb ??= new StringBuilder();
            sb.Append(text, p, j - p);
            sb.Append(bywhat);
            j += word.Length;
            p = j;
        }
        else j++;
    if (sb == null) return text;
    sb.Append(text, p, text.Length - p);
    return sb.ToString();
}

您可以使用string.replace

string input = "test, and test but not testing.  But yes to test";
string result2 = input.Replace("test", "text");
Console.WriteLine(input);
Console.WriteLine(result2);
Console.ReadLine();