我用这个来纠正名字。它的基本原理是，如果字符遵循特定的模式，则将其更改为大写。在这种情况下，我选择了空格和“Mc”的破折号。

private String CorrectName(String name)
{
    List<String> StringsToCapitalizeAfter = new List<String>() { " ", "-", "Mc" };
    StringBuilder NameBuilder = new StringBuilder();
    name.Select(c => c.ToString()).ToList().ForEach(c =>
    {
        c = c.ToLower();
        StringsToCapitalizeAfter.ForEach(s =>
        {
            if(String.IsNullOrEmpty(NameBuilder.ToString()) ||
               NameBuilder.ToString().EndsWith(s))
            {
                c = c.ToUpper();
            }
        });
        NameBuilder.Append(c);
    });
    return NameBuilder.ToString();
}

如果你只关心第一个字母是否大写，而不关心字符串的其他部分，你可以只选择第一个字符，使其大写，并将其与没有原始第一个字符的字符串的其余部分连接起来。

String word ="red house";
word = word[0].ToString().ToUpper() + word.Substring(1, word.length -1);
//result: word = "Red house"

我们需要将第一个字符转换为ToString()，因为我们将其作为Char数组读取，而Char类型没有ToUpper()方法。

string input = "red HOUSE";
System.Text.StringBuilder sb = new System.Text.StringBuilder(input);

for (int j = 0; j < sb.Length; j++)
{
    if ( j == 0 ) //catches just the first letter
        sb[j] = System.Char.ToUpper(sb[j]);
    else  //everything else is lower case
        sb[j] = System.Char.ToLower(sb[j]);
}
// Store the new string.
string corrected = sb.ToString();
System.Console.WriteLine(corrected);

正确的方法是使用文化:

System.Globalization.CultureInfo.CurrentCulture.TextInfo.ToTitleCase(word.ToLower())

注意:这将大写字符串中的每个单词，例如:“红房子”——>“红房子”。该解决方案还将减少单词中的大写字母，例如:"old McDonald"——> "old McDonald"。

由于这个问题是关于最大化性能的，我采用了Darren的版本来使用跨度，这减少了垃圾，并提高了大约10%的速度。

/// <summary>
/// Returns the input string with the first character converted to uppercase
/// </summary>
public static string ToUpperFirst(this string s)
{
    if (string.IsNullOrEmpty(s))
        throw new ArgumentException("There is no first letter");

    Span<char> a = stackalloc char[s.Length];
    s.AsSpan(1).CopyTo(a.Slice(1));
    a[0] = char.ToUpper(s[0]);
    return new string(a);
}

性能

完整的测试代码

using System;
using System.Linq;

using BenchmarkDotNet.Attributes;

namespace CorePerformanceTest
{
    public class StringUpperTest
    {
        [Params("red", "red house")]
        public string Data;

        [Benchmark]
        public string Carlos() => Data.Carlos();

        [Benchmark]
        public string Darren() => Data.Darren();

        [Benchmark]
        public string Marcell() => Data.Marcell();
    }

    internal static class StringExtensions
    {
        public static string Carlos(this string input) =>
            input switch
            {
                null => throw new ArgumentNullException(nameof(input)),
                "" => throw new ArgumentException($"{nameof(input)} cannot be empty", nameof(input)),
                _ => input.First().ToString().ToUpper() + input.Substring(1)
            };

        public static string Darren(this string s)
        {
            if (string.IsNullOrEmpty(s))
                throw new ArgumentException("There is no first letter");

            char[] a = s.ToCharArray();
            a[0] = char.ToUpper(a[0]);
            return new string(a);
        }

        public static string Marcell(this string s)
        {
            if (string.IsNullOrEmpty(s))
                throw new ArgumentException("There is no first letter");

            Span<char> a = stackalloc char[s.Length];
            s.AsSpan(1).CopyTo(a.Slice(1));
            a[0] = char.ToUpper(s[0]);
            return new string(a);
        }
    }

}

扩展Carlos上面的问题，如果你想要大写多个句子，你可以使用下面的代码:

    /// <summary>
    /// Capitalize first letter of every sentence. 
    /// </summary>
    /// <param name="inputSting"></param>
    /// <returns></returns>
    public string CapitalizeSentences (string inputSting)
    {
        string result = string.Empty;
        if (!string.IsNullOrEmpty(inputSting))
        {
            string[] sentences = inputSting.Split('.');

            foreach (string sentence in sentences)
            {
                result += string.Format ("{0}{1}.", sentence.First().ToString().ToUpper(), sentence.Substring(1)); 
            }
        }

        return result; 
    }