replaceAll("(?<=[^^\\p{Uppercase}])(?=[\\p{Uppercase}])"," ");

发现很多这些答案是相当迟钝的，但我还没有完全测试我的解决方案，但它适用于我需要的，应该处理首字母缩略词，并且比其他IMO更紧凑/可读:

private string CamelCaseToSpaces(string s)
    {
        if (string.IsNullOrEmpty(s)) return string.Empty;

        StringBuilder stringBuilder = new StringBuilder();
        for (int i = 0; i < s.Length; i++)
        {
            stringBuilder.Append(s[i]);

            int nextChar = i + 1;
            if (nextChar < s.Length && char.IsUpper(s[nextChar]) && !char.IsUpper(s[i]))
            {
                stringBuilder.Append(" ");
            }
        }

        return stringBuilder.ToString();
    }

这对聚合来说是个好机会。它被设计成可读的，但不一定特别快。

someString
.Aggregate(
   new StringBuilder(),
   (str, ch) => {
      if (char.IsUpper(ch) && str.Length > 0)
         str.Append(" ");
      str.Append(ch);
      return str;
   }
).ToString();

我想用这个

string InsertSpace(string text ) {
    return string.Join("" , text.Select(ch => char.IsUpper(ch) ? " " : "" + ch))  ;
} 

我开始做一个简单的扩展方法，基于二进制Worrier的代码，它将正确地处理首字母缩略词，并且是可重复的(不会破坏已经间隔的单词)。这是我的结果。

public static string UnPascalCase(this string text)
{
    if (string.IsNullOrWhiteSpace(text))
        return "";
    var newText = new StringBuilder(text.Length * 2);
    newText.Append(text[0]);
    for (int i = 1; i < text.Length; i++)
    {
        var currentUpper = char.IsUpper(text[i]);
        var prevUpper = char.IsUpper(text[i - 1]);
        var nextUpper = (text.Length > i + 1) ? char.IsUpper(text[i + 1]) || char.IsWhiteSpace(text[i + 1]): prevUpper;
        var spaceExists = char.IsWhiteSpace(text[i - 1]);
        if (currentUpper && !spaceExists && (!nextUpper || !prevUpper))
                newText.Append(' ');
        newText.Append(text[i]);
    }
    return newText.ToString();
}

下面是这个函数通过的单元测试用例。我把他建议的大部分案例都加到了这个清单上。其中三个没有通过的(两个只是罗马数字)被注释掉了:

Assert.AreEqual("For You And I", "ForYouAndI".UnPascalCase());
Assert.AreEqual("For You And The FBI", "ForYouAndTheFBI".UnPascalCase());
Assert.AreEqual("A Man A Plan A Canal Panama", "AManAPlanACanalPanama".UnPascalCase());
Assert.AreEqual("DNS Server", "DNSServer".UnPascalCase());
Assert.AreEqual("For You And I", "For You And I".UnPascalCase());
Assert.AreEqual("Mount Mᶜ Kinley National Park", "MountMᶜKinleyNationalPark".UnPascalCase());
Assert.AreEqual("El Álamo Tejano", "ElÁlamoTejano".UnPascalCase());
Assert.AreEqual("The Ævar Arnfjörð Bjarmason", "TheÆvarArnfjörðBjarmason".UnPascalCase());
Assert.AreEqual("Il Caffè Macchiato", "IlCaffèMacchiato".UnPascalCase());
//Assert.AreEqual("Mister Dženan Ljubović", "MisterDženanLjubović".UnPascalCase());
//Assert.AreEqual("Ole King Henry Ⅷ", "OleKingHenryⅧ".UnPascalCase());
//Assert.AreEqual("Carlos Ⅴº El Emperador", "CarlosⅤºElEmperador".UnPascalCase());
Assert.AreEqual("For You And The FBI", "For You And The FBI".UnPascalCase());
Assert.AreEqual("A Man A Plan A Canal Panama", "A Man A Plan A Canal Panama".UnPascalCase());
Assert.AreEqual("DNS Server", "DNS Server".UnPascalCase());
Assert.AreEqual("Mount Mᶜ Kinley National Park", "Mount Mᶜ Kinley National Park".UnPascalCase());

二进制担忧者，我已经使用了你建议的代码，它是相当好的，我只是有一个小的增加:

public static string AddSpacesToSentence(string text)
{
    if (string.IsNullOrEmpty(text))
        return "";
    StringBuilder newText = new StringBuilder(text.Length * 2);
    newText.Append(text[0]);
            for (int i = 1; i < result.Length; i++)
            {
                if (char.IsUpper(result[i]) && !char.IsUpper(result[i - 1]))
                {
                    newText.Append(' ');
                }
                else if (i < result.Length)
                {
                    if (char.IsUpper(result[i]) && !char.IsUpper(result[i + 1]))
                        newText.Append(' ');

                }
                newText.Append(result[i]);
            }
    return newText.ToString();
}

我添加了一个条件!char。IsUpper(text[i - 1])。这修复了一个错误，会导致'AverageNOX'变成'平均NOX'，这显然是错误的，因为它应该读'平均NOX'。

遗憾的是，这仍然有错误，如果你有文本'FromAStart'，你会得到'FromAStart'出来。

有什么解决办法吗?