首先使用ToLower()，然后对结果使用CultureInfo.CurrentCulture.TextInfo.ToTitleCase以获得正确的输出。

    //---------------------------------------------------------------
    // Get title case of a string (every word with leading upper case,
    //                             the rest is lower case)
    //    i.e: ABCD EFG -> Abcd Efg,
    //         john doe -> John Doe,
    //         miXEd CaSING - > Mixed Casing
    //---------------------------------------------------------------
    public static string ToTitleCase(string str)
    {
        return CultureInfo.CurrentCulture.TextInfo.ToTitleCase(str.ToLower());
    }

不使用TextInfo:

public static string TitleCase(this string text, char seperator = ' ') =>
  string.Join(seperator, text.Split(seperator).Select(word => new string(
    word.Select((letter, i) => i == 0 ? char.ToUpper(letter) : char.ToLower(letter)).ToArray())));

它循环每个单词中的每个字母，如果它是第一个字母，则将其转换为大写字母，否则将其转换为小写字母。

下面是这个问题的解决方案……

CultureInfo cultureInfo = Thread.CurrentThread.CurrentCulture;
TextInfo textInfo = cultureInfo.TextInfo;
string txt = textInfo.ToTitleCase(txt);

即使是驼色大小写也能正常工作:'someText in YourPage'

public static class StringExtensions
{
    /// <summary>
    /// Title case example: 'Some Text In Your Page'.
    /// </summary>
    /// <param name="text">Support camel and title cases combinations: 'someText in YourPage'</param>
    public static string ToTitleCase(this string text)
    {
        if (string.IsNullOrEmpty(text))
        {
            return text;
        }
        var result = string.Empty;
        var splitedBySpace = text.Split(new[]{ ' ' }, StringSplitOptions.RemoveEmptyEntries);
        foreach (var sequence in splitedBySpace)
        {
            // let's check the letters. Sequence can contain even 2 words in camel case
            for (var i = 0; i < sequence.Length; i++)
            {
                var letter = sequence[i].ToString();
                // if the letter is Big or it was spaced so this is a start of another word
                if (letter == letter.ToUpper() || i == 0)
                {
                    // add a space between words
                    result += ' ';
                }
                result += i == 0 ? letter.ToUpper() : letter;
            }
        }
        return result.Trim();
    }
}

最好通过尝试自己的代码来理解…

阅读更多

http://www.stupidcodes.com/2014/04/convert-string-to-uppercase-proper-case.html

1)将字符串转换为大写

string lower = "converted from lowercase";
Console.WriteLine(lower.ToUpper());

2)将字符串转换为小写

string upper = "CONVERTED FROM UPPERCASE";
Console.WriteLine(upper.ToLower());

3)转换String为TitleCase

    CultureInfo cultureInfo = Thread.CurrentThread.CurrentCulture;
    TextInfo textInfo = cultureInfo.TextInfo;
    string txt = textInfo.ToTitleCase(TextBox1.Text());

首先使用ToLower()，然后对结果使用CultureInfo.CurrentCulture.TextInfo.ToTitleCase以获得正确的输出。

    //---------------------------------------------------------------
    // Get title case of a string (every word with leading upper case,
    //                             the rest is lower case)
    //    i.e: ABCD EFG -> Abcd Efg,
    //         john doe -> John Doe,
    //         miXEd CaSING - > Mixed Casing
    //---------------------------------------------------------------
    public static string ToTitleCase(string str)
    {
        return CultureInfo.CurrentCulture.TextInfo.ToTitleCase(str.ToLower());
    }