这个问题有点老了，但现在在Nuget上有一个很好的库，它可以做到这一点，以及许多其他转换到人类可读的文本。

在GitHub或Nuget上检查Humanizer。

例子

"PascalCaseInputStringIsTurnedIntoSentence".Humanize() => "Pascal case input string is turned into sentence"
"Underscored_input_string_is_turned_into_sentence".Humanize() => "Underscored input string is turned into sentence"
"Underscored_input_String_is_turned_INTO_sentence".Humanize() => "Underscored input String is turned INTO sentence"

// acronyms are left intact
"HTML".Humanize() => "HTML"

我知道这是一个旧的，但这是一个扩展我使用当我需要这样做:

public static class Extensions
{
    public static string ToSentence( this string Input )
    {
        return new string(Input.SelectMany((c, i) => i > 0 && char.IsUpper(c) ? new[] { ' ', c } : new[] { c }).ToArray());
    }
}

这将允许您使用MyCasedString.ToSentence()

下面是在SQL中如何做到这一点

create  FUNCTION dbo.PascalCaseWithSpace(@pInput AS VARCHAR(MAX)) RETURNS VARCHAR(MAX)
BEGIN
    declare @output varchar(8000)

set @output = ''


Declare @vInputLength        INT
Declare @vIndex              INT
Declare @vCount              INT
Declare @PrevLetter varchar(50)
SET @PrevLetter = ''

SET @vCount = 0
SET @vIndex = 1
SET @vInputLength = LEN(@pInput)

WHILE @vIndex <= @vInputLength
BEGIN
    IF ASCII(SUBSTRING(@pInput, @vIndex, 1)) = ASCII(Upper(SUBSTRING(@pInput, @vIndex, 1)))
       begin 

        if(@PrevLetter != '' and ASCII(@PrevLetter) = ASCII(Lower(@PrevLetter)))
            SET @output = @output + ' ' + SUBSTRING(@pInput, @vIndex, 1)
            else
            SET @output = @output +  SUBSTRING(@pInput, @vIndex, 1) 

        end
    else
        begin
        SET @output = @output +  SUBSTRING(@pInput, @vIndex, 1) 

        end

set @PrevLetter = SUBSTRING(@pInput, @vIndex, 1) 

    SET @vIndex = @vIndex + 1
END


return @output
END

具有fold的实现，也称为Aggregate:

    public static string SpaceCapitals(this string arg) =>
       new string(arg.Aggregate(new List<Char>(),
                      (accum, x) => 
                      {
                          if (Char.IsUpper(x) &&
                              accum.Any() &&
                              // prevent double spacing
                              accum.Last() != ' ' &&
                              // prevent spacing acronyms (ASCII, SCSI)
                              !Char.IsUpper(accum.Last()))
                          {
                              accum.Add(' ');
                          }

                          accum.Add(x);

                          return accum;
                      }).ToArray());

除了请求之外，这个实现还正确地保存了开头、内部、结尾空格和首字母缩写，例如，

" SpacedWord " => " Spaced Word ",  

"Inner Space" => "Inner Space",  

"SomeACRONYM" => "Some ACRONYM".

这个正则表达式在每个大写字母前放置一个空格字符:

using System.Text.RegularExpressions;

const string myStringWithoutSpaces = "ThisIsAStringWithoutSpaces";
var myStringWithSpaces = Regex.Replace(myStringWithoutSpaces, "([A-Z])([a-z]*)", " $1$2");

注意前面的空间，如果“$1$2”，这是可以完成的。

结果如下:

"This Is A String Without Spaces"

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());