C# 将字符串转换为标题大小写

我需要将以下内容转换为标题案例：

短语中的第一个单词

换句话说，在同一短语中，长度大于minLength

我在看，但结果不是预期的

因此，minLength=2的短语“汽车非常快”将变成“汽车非常快” 快”

我能够使用以下命令生成第一个大写单词：

Char[] letters = source.ToCharArray();
letters[0] = Char.ToUpper(letters[0]);

为了得到我所说的话：

Regex.Matches(source, @"\b(\w|['-])+\b"

但我不知道如何把这些放在一起

谢谢,， 米格尔

示例代码：

string input = "i have the car which is very fast";
int minLength = 2;
string regexPattern = string.Format(@"^\w|\b\w(?=\w{{{0}}})", minLength);
string output = Regex.Replace(input, regexPattern, m => m.Value.ToUpperInvariant());

更新（适用于单个字符串中有多个句子的情况）

您可能希望处理

、
？
和其他符号，然后可以使用以下符号。您可以添加任意数量的句子终止符号

string input = "i have the car which is very fast! me is slow.";
int minLength = 2;
string regexPattern = string.Format(@"(?<=(^|[.!?])\s*)\w|\b\w(?=\w{{{0}}})", minLength);
string output = Regex.Replace(input, regexPattern, m => m.Value.ToUpperInvariant());

一种不需要正则表达式的替代（且简单）解决方案是使用String.Split方法和
列表。选择
函数映射复杂条件：

var text = @"i have the car which is very fast. me is slow.";
var length = 2;
var first = true; // first word in the sentence
var containsDot = false; // previous word contains a dot
var result = text
                .Split(' ')
                .ToList()
                .Select (p => 
                    {
                        if (first)
                        {
                            p = FirstCharToUpper(p);
                            first = false;
                        }
                        if (containsDot)
                        {
                            p = FirstCharToUpper(p);
                            containsDot = false;
                        }
                        containsDot = p.Contains(".");
                        if (p.Length > length)
                        {
                            return FirstCharToUpper(p);
                        }
                        return p;
                    })
                .Aggregate ((h, t) => h + " " + t);
Console.WriteLine(result);

输出为：

I Have The Car Which is Very Fast. Me is Slow.

firstChartUpper
方法如下：

此解决方案的缺点是：条件越复杂，select语句就越复杂/不可读，但它是正则表达式的替代品。
英文标题大小写极其复杂。而且它是不可计算的。句号

你能得到的最好的方法是根据你的喜好列表改变所有的小词。对于所有的口头表达，这仍然是错误的。虽然扩展的变体列表可以捕获其中的许多变体，但是如果没有语义分析，仍然无法确定其中的一些变体。两个例子：


空车上运行/空车上运行
在建筑物上工作

后者确实从上下文中变得清晰；前者并非如此。意思上有明显的区别，但计算机无法决定哪个是对的

（有时甚至人类也不能。我问了StackExchnge论坛的第一个例子，但没有得到可接受的答案。）

以下是我喜欢的替代品清单；但有些四个字母的单词（不是双关语）是个人的选择。还有一些人可能会争辩说，所有类型的数字，像任何、所有、很少的数字一样，都应该大写

这一点也不优雅，事实上这是一种尴尬。但它对我来说效果相当好，所以我定期使用它，并通过它提供了10多万个标题

public string ETC(string title)
{  // english title capitalization
    if (title == null) return "";

    string s = title.Trim().Replace('`', '\'');      // change apo to tick mark

    TextInfo UsaTextInfo = new CultureInfo("en-US", false).TextInfo;
    s = UsaTextInfo.ToTitleCase(s);              // caps for all words

    // a list of exceptions one way or the other..
    s = s.Replace(" A ", " a ");
    s = s.Replace(" also ", " Also ");
    s = s.Replace(" An ", " an ");
    s = s.Replace(" And ", " and ");
    s = s.Replace(" as ", " As ");
    s = s.Replace(" At ", " at ");
    s = s.Replace(" be ", " Be ");
    s = s.Replace(" But ", " But ");
    s = s.Replace(" By ", " by ");
    s = s.Replace(" For ", " for ");
    s = s.Replace(" From ", " from ");
    s = s.Replace(" if ", " If ");
    s = s.Replace(" In ", " in ");
    s = s.Replace(" Into ", " into ");
    s = s.Replace(" he ", " He ");
    s = s.Replace(" has ", " Has ");
    s = s.Replace(" had ", " Had ");
    s = s.Replace(" is ", " Is ");
    s = s.Replace(" my ", " My ");
    s = s.Replace("   ", "  ");                // no triple spaces
    s = s.Replace("'N'", "'n'");          // Rock 'n' Roll
    s = s.Replace("'N'", "'n'");         // Rock 'n Roll
    s = s.Replace(" no ", " No ");
    s = s.Replace(" Nor ", " nor ");
    s = s.Replace(" Not ", " not ");
    s = s.Replace(" Of ", " of ");
    s = s.Replace(" Off ", " off ");
    s = s.Replace(" On ", " on ");
    s = s.Replace(" Onto ", " onto ");
    s = s.Replace(" Or ", " or ");
    s = s.Replace(" O'c ", " O'C ");
    s = s.Replace(" Over ", " over ");
    s = s.Replace(" so ", " So ");
    s = s.Replace(" To ", " to ");
    s = s.Replace(" that ", " That ");
    s = s.Replace(" this ", " This ");
    s = s.Replace(" thus ", " Thus ");
    s = s.Replace(" The ", " the ");
    s = s.Replace(" Too ", " too ");
    s = s.Replace(" when ", " When ");
    s = s.Replace(" With ", " with ");
    s = s.Replace(" Up ", " up ");
    s = s.Replace(" Yet ", " yet ");
    // a few(!) verbal expressions
    s = s.Replace(" Get up ", " Get Up ");
    s = s.Replace(" Give up ", " Give Up ");
    s = s.Replace(" Givin' up ", " Givin' Up ");
    s = s.Replace(" Grow up ", " Grow Up ");
    s = s.Replace(" Hung up ", " Hung Up ");
    s = s.Replace(" Make up ", " Make Up ");
    s = s.Replace(" Wake Me up ", " Wake Me Up ");
    s = s.Replace(" Mixed up ", " Mixed Up ");
    s = s.Replace(" Shut up ", " Shut Up ");
    s = s.Replace(" Stand up ", " Stand Up ");            
    s = s.Replace(" Wind up ", " Wind Up ");
    s = s.Replace(" Wake up ", " Wake Up ");
    s = s.Replace(" Come up ", " Come Up ");
    s = s.Replace(" Working on ", " Working On ");
    s = s.Replace(" Waiting on ", " Waiting On ");
    s = s.Replace(" Turn on ", " Turn On ");
    s = s.Replace(" Move on ", " Move On ");
    s = s.Replace(" Keep on ", " Keep On ");
    s = s.Replace(" Bring It on ", " Bring It On ");
    s = s.Replace(" Hold on ", " Hold On ");
    s = s.Replace(" Hang on ", " Hang On ");
    s = s.Replace(" Go on ", " Go On ");
    s = s.Replace(" Coming on ", " Coming On ");
    s = s.Replace(" Come on ", " Come On ");
    s = s.Replace(" Call on ", " Call On ");
    s = s.Replace(" Trust in ", " Trust In ");
    s = s.Replace(" Fell in ", " Fell In ");
    s = s.Replace(" Falling in ", " Falling In ");
    s = s.Replace(" Fall in ", " Fall In ");
    s = s.Replace(" Faith in ", " Faith In ");
    s = s.Replace(" Come in ", " Come In ");
    s = s.Replace(" Believe in ", " Believe In ");



    return s.Trim();
}

注意，仍然有很多规则不能像这样实现

有些基本规则并不难：第一个和最后一个单词大写。所有动词（Is）、形容词（Red）、promouns（He）、名词（Ace）和数字（One），即使它们的字母少于3个（或4个）

但例外情况很难，例如：当介词是动词表达的一部分或一个时，不要大写

例1：“在建筑物上工作”-你必须知道这是一首福音歌，才能决定它是“开着的”

示例2:“正在运行/空运行”。可能表示“正在运行”或“正在运行（使用气体指示器）”或“空”

因此，最终您将不得不接受折衷。
以下是一种使用
StringBuilder
和纯字符串方法的方法，不需要使用正则表达式，因此它应该非常有效：

public static string ToTitleCase(string input, int minLength = 0)
{
    TextInfo ti = CultureInfo.CurrentCulture.TextInfo;
    string titleCaseDefault = ti.ToTitleCase(input);
    if (minLength == 0)
        return titleCaseDefault;
    StringBuilder sb = new StringBuilder(titleCaseDefault.Length);
    int wordCount = 0;
    char[] wordSeparatorChars = " \t\n.,;-:".ToCharArray();

    for (int i = 0; i < titleCaseDefault.Length; i++)
    {
        char c = titleCaseDefault[i];
        bool nonSpace = !char.IsWhiteSpace(c);
        if (nonSpace)
        {
            wordCount++;
            int firstSpace = titleCaseDefault.IndexOfAny(wordSeparatorChars, i);
            int endIndex = firstSpace >= 0 ? firstSpace : titleCaseDefault.Length;
            string word = titleCaseDefault.Substring(i, endIndex - i);
            if (wordCount == 1) // first word upper
                sb.Append(word);
            else
                sb.Append(word.Length < minLength ? word.ToLower() : ti.ToTitleCase(word));
            i = endIndex - 1;
        }
        else
            sb.Append(c);
    }
    return sb.ToString();
}

现在试过了吗？我刚刚更新了我的问题以显示我试过的内容。如果minLength为2，为什么“
太短而不能用标题大小写？@TimSchmelter Cause OP陈述了
哪个长度高于minLength
@UlugbekUmirov:所以
minLength
实际上不够min；）如何将您的示例扩展到所有长度大于2的单词，以及第一个单词和点后的单词，即使它们的长度小于2？我进行了测试，它似乎可以正常工作，只有一个例外。如果我有一个像“e-marketing”这样的词，我希望它变成“e-marketing”，在这一刻我得到了“e-marketing”。用你的例子能解决这个问题吗？感谢You@MDMoura添加了
-
@MDMoura的处理，不应该是正确的标题案例“电子营销”（类似于“电子商务”）？@elgonzo没有严格的规则：
I Have The Car Which is Very Fast. Me is Slow.

public static string FirstCharToUpper(string input)
{
    if (String.IsNullOrEmpty(input))
        throw new ArgumentException("ARGH!");
    return input.First().ToString().ToUpper() + String.Join("", input.Skip(1));
}

public string ETC(string title)
{  // english title capitalization
    if (title == null) return "";

    string s = title.Trim().Replace('`', '\'');      // change apo to tick mark

    TextInfo UsaTextInfo = new CultureInfo("en-US", false).TextInfo;
    s = UsaTextInfo.ToTitleCase(s);              // caps for all words

    // a list of exceptions one way or the other..
    s = s.Replace(" A ", " a ");
    s = s.Replace(" also ", " Also ");
    s = s.Replace(" An ", " an ");
    s = s.Replace(" And ", " and ");
    s = s.Replace(" as ", " As ");
    s = s.Replace(" At ", " at ");
    s = s.Replace(" be ", " Be ");
    s = s.Replace(" But ", " But ");
    s = s.Replace(" By ", " by ");
    s = s.Replace(" For ", " for ");
    s = s.Replace(" From ", " from ");
    s = s.Replace(" if ", " If ");
    s = s.Replace(" In ", " in ");
    s = s.Replace(" Into ", " into ");
    s = s.Replace(" he ", " He ");
    s = s.Replace(" has ", " Has ");
    s = s.Replace(" had ", " Had ");
    s = s.Replace(" is ", " Is ");
    s = s.Replace(" my ", " My ");
    s = s.Replace("   ", "  ");                // no triple spaces
    s = s.Replace("'N'", "'n'");          // Rock 'n' Roll
    s = s.Replace("'N'", "'n'");         // Rock 'n Roll
    s = s.Replace(" no ", " No ");
    s = s.Replace(" Nor ", " nor ");
    s = s.Replace(" Not ", " not ");
    s = s.Replace(" Of ", " of ");
    s = s.Replace(" Off ", " off ");
    s = s.Replace(" On ", " on ");
    s = s.Replace(" Onto ", " onto ");
    s = s.Replace(" Or ", " or ");
    s = s.Replace(" O'c ", " O'C ");
    s = s.Replace(" Over ", " over ");
    s = s.Replace(" so ", " So ");
    s = s.Replace(" To ", " to ");
    s = s.Replace(" that ", " That ");
    s = s.Replace(" this ", " This ");
    s = s.Replace(" thus ", " Thus ");
    s = s.Replace(" The ", " the ");
    s = s.Replace(" Too ", " too ");
    s = s.Replace(" when ", " When ");
    s = s.Replace(" With ", " with ");
    s = s.Replace(" Up ", " up ");
    s = s.Replace(" Yet ", " yet ");
    // a few(!) verbal expressions
    s = s.Replace(" Get up ", " Get Up ");
    s = s.Replace(" Give up ", " Give Up ");
    s = s.Replace(" Givin' up ", " Givin' Up ");
    s = s.Replace(" Grow up ", " Grow Up ");
    s = s.Replace(" Hung up ", " Hung Up ");
    s = s.Replace(" Make up ", " Make Up ");
    s = s.Replace(" Wake Me up ", " Wake Me Up ");
    s = s.Replace(" Mixed up ", " Mixed Up ");
    s = s.Replace(" Shut up ", " Shut Up ");
    s = s.Replace(" Stand up ", " Stand Up ");            
    s = s.Replace(" Wind up ", " Wind Up ");
    s = s.Replace(" Wake up ", " Wake Up ");
    s = s.Replace(" Come up ", " Come Up ");
    s = s.Replace(" Working on ", " Working On ");
    s = s.Replace(" Waiting on ", " Waiting On ");
    s = s.Replace(" Turn on ", " Turn On ");
    s = s.Replace(" Move on ", " Move On ");
    s = s.Replace(" Keep on ", " Keep On ");
    s = s.Replace(" Bring It on ", " Bring It On ");
    s = s.Replace(" Hold on ", " Hold On ");
    s = s.Replace(" Hang on ", " Hang On ");
    s = s.Replace(" Go on ", " Go On ");
    s = s.Replace(" Coming on ", " Coming On ");
    s = s.Replace(" Come on ", " Come On ");
    s = s.Replace(" Call on ", " Call On ");
    s = s.Replace(" Trust in ", " Trust In ");
    s = s.Replace(" Fell in ", " Fell In ");
    s = s.Replace(" Falling in ", " Falling In ");
    s = s.Replace(" Fall in ", " Fall In ");
    s = s.Replace(" Faith in ", " Faith In ");
    s = s.Replace(" Come in ", " Come In ");
    s = s.Replace(" Believe in ", " Believe In ");



    return s.Trim();
}

public static string ToTitleCase(string input, int minLength = 0)
{
    TextInfo ti = CultureInfo.CurrentCulture.TextInfo;
    string titleCaseDefault = ti.ToTitleCase(input);
    if (minLength == 0)
        return titleCaseDefault;
    StringBuilder sb = new StringBuilder(titleCaseDefault.Length);
    int wordCount = 0;
    char[] wordSeparatorChars = " \t\n.,;-:".ToCharArray();

    for (int i = 0; i < titleCaseDefault.Length; i++)
    {
        char c = titleCaseDefault[i];
        bool nonSpace = !char.IsWhiteSpace(c);
        if (nonSpace)
        {
            wordCount++;
            int firstSpace = titleCaseDefault.IndexOfAny(wordSeparatorChars, i);
            int endIndex = firstSpace >= 0 ? firstSpace : titleCaseDefault.Length;
            string word = titleCaseDefault.Substring(i, endIndex - i);
            if (wordCount == 1) // first word upper
                sb.Append(word);
            else
                sb.Append(word.Length < minLength ? word.ToLower() : ti.ToTitleCase(word));
            i = endIndex - 1;
        }
        else
            sb.Append(c);
    }
    return sb.ToString();
}

string text =  "the car is very fast";
string output = ToTitleCase(text, 3);