使字符串的第一个字母大写(以最大性能)

我有一个带有文本框的DetailsView 我希望输入的数据总是以大写的第一个字母保存。

例子:

"red" --> "Red"
"red house" --> " Red house"

我怎样才能实现性能最大化呢?

注意:

Based on the answers and the comments under the answers, many people think this is asking about capitalizing all words in the string. E.g. => Red House It isn't, but if that is what you seek, look for one of the answers that uses TextInfo's ToTitleCase method. (Note: Those answers are incorrect for the question actually asked.) See TextInfo.ToTitleCase documentation for caveats (doesn't touch all-caps words - they are considered acronyms; may lowercase letters in middle of words that "shouldn't" be lowered, e.g., "McDonald" → "Mcdonald"; not guaranteed to handle all culture-specific subtleties re capitalization rules.)

注意:

第一个字母之后的字母是否必须小写，这个问题很模糊。公认的答案假定只有第一个字母需要修改。如果要强制字符串中除第一个字母外的所有字母都小写，请查找包含ToLower且不包含ToTitleCase的答案。

当前回答

最简单和最快的方法是将字符串的第一个字符替换为大写字符:

string str = "test";<br>
str = str.Replace(str[0], char.ToUpper(str[0]));

2013-09-19 10:40:05

其他回答

下面是对我有用的代码:

private string StringLetterUppercase(string input)
{
    if (input == null)
    {
        throw new ArgumentNullException(nameof(input));
    }
    else if (input == "")
    {
        throw new ArgumentException($"{nameof(input)} cannot be empty", nameof(input));
    }
    else
    {
        return input.First().ToString().ToUpper() + input.Substring(1);
    }
}

2021-06-11 02:05:41

public string FirstLetterToUpper(string str)
{
    if (str == null)
        return null;

    if (str.Length > 1)
        return char.ToUpper(str[0]) + str.Substring(1);

    return str.ToUpper();
}

旧的回答: 这使得每个首字母都是大写的

public string ToTitleCase(string str)
{
    return CultureInfo.CurrentCulture.TextInfo.ToTitleCase(str.ToLower());
}

2010-11-09 15:39:36

string s_Val = "test";
if (s_Val != "")
{
   s_Val  = char.ToUpper(s_Val[0]);
   if (s_Val.Length > 1)
   {
      s_Val += s_Val.Substring(1);
   }
 }

2010-11-09 15:27:04

我从c#大写首字母- Dot Net Perls中获得了最快的方法，并将其转换为扩展方法:

    /// <summary>
    /// Returns the input string with the first character converted to uppercase, or mutates any nulls passed into string.Empty
    /// </summary>
    public static string FirstLetterToUpperCaseOrConvertNullToEmptyString(this string s)
    {
        if (string.IsNullOrEmpty(s))
            return string.Empty;

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

注意:使用ToCharArray比替代char.ToUpper(s[0]) + s.Substring(1)更快的原因是只分配了一个字符串，而Substring方法为子字符串分配了一个字符串，然后再分配一个字符串来组成最终结果。

下面是这种方法的样子，结合CarlosMuñoz接受的答案的初始测试:

    /// <summary>
    /// Returns the input string with the first character converted to uppercase
    /// </summary>
    public static string FirstLetterToUpperCase(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);
    }

2014-11-22 04:03:50

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; 
    }

2017-11-30 19:39:45

使字符串的第一个字母大写(以最大性能)

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