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

我认为下面的方法是最好的解决方案。

class Program
{
    static string UppercaseWords(string value)
    {
        char[] array = value.ToCharArray();
        // Handle the first letter in the string.
        if (array.Length >= 1)
        {
            if (char.IsLower(array[0]))
            {
                array[0] = char.ToUpper(array[0]);
            }
        }
        // Scan through the letters, checking for spaces.
        // ... Uppercase the lowercase letters following spaces.
        for (int i = 1; i < array.Length; i++)
        {
            if (array[i - 1] == ' ')
            {
                if (char.IsLower(array[i]))
                {
                    array[i] = char.ToUpper(array[i]);
                }
            }
        }
        return new string(array);
    }

    static void Main()
    {
        // Uppercase words in these strings.
        const string value1 = "something in the way";
        const string value2 = "dot net PERLS";
        const string value3 = "String_two;three";
        const string value4 = " sam";
        // ... Compute the uppercase strings.
        Console.WriteLine(UppercaseWords(value1));
        Console.WriteLine(UppercaseWords(value2));
        Console.WriteLine(UppercaseWords(value3));
        Console.WriteLine(UppercaseWords(value4));
    }
}

Output

Something In The Way
Dot Net PERLS
String_two;three
 Sam

参考

2018-10-29 00:45:48

其他回答

这就可以了，尽管它也会确保没有错误的大写字母不是在单词的开头。

public string(string s)
{
    System.Globalization.CultureInfo c = new System.Globalization.CultureInfo("en-us", false)
    System.Globalization.TextInfo t = c.TextInfo;

    return t.ToTitleCase(s);
}

2010-11-09 15:40:45

下面的函数对所有方式都是正确的:

static string UppercaseWords(string value)
{
    char[] array = value.ToCharArray();
    // Handle the first letter in the string.
    if (array.Length >= 1)
    {
        if (char.IsLower(array[0]))
        {
            array[0] = char.ToUpper(array[0]);
        }
    }
    // Scan through the letters, checking for spaces.
    // ... Uppercase the lowercase letters following spaces.
    for (int i = 1; i < array.Length; i++)
    {
        if (array[i - 1] == ' ')
        {
            if (char.IsLower(array[i]))
            {
                array[i] = char.ToUpper(array[i]);
            }
        }
    }
    return new string(array);
}

我在这里找到的。

2017-02-08 19:23:00

FluentSharp有lowerCaseFirstLetter方法来做这个。

2015-07-21 17:25:20

最快的方法:

private string Capitalize(string s){
    if (string.IsNullOrEmpty(s))
    {
        return string.Empty;
    }
    char[] a = s.ToCharArray();
    a[0] = char.ToUpper(a[0]);
    return new string(a);
}

测试显示下一个结果(有1,000,000个符号作为输入的字符串):

测试结果

2016-04-13 04:33:16

这里有一个方法来做它作为一个扩展方法:

static public string UpperCaseFirstCharacter(this string text)
{
    if (!string.IsNullOrEmpty(text))
    {
        return string.Format(
            "{0}{1}",
            text.Substring(0, 1).ToUpper(),
            text.Substring(1));
    }

    return text;
}

然后可以像这样调用它:

//yields "This is Brian's test.":
"this is Brian's test.".UpperCaseFirstCharacter();

下面是一些单元测试:

[Test]
public void UpperCaseFirstCharacter_ZeroLength_ReturnsOriginal()
{
    string orig = "";
    string result = orig.UpperCaseFirstCharacter();

    Assert.AreEqual(orig, result);
}

[Test]
public void UpperCaseFirstCharacter_SingleCharacter_ReturnsCapital()
{
    string orig = "c";
    string result = orig.UpperCaseFirstCharacter();

    Assert.AreEqual("C", result);
}

[Test]
public void UpperCaseFirstCharacter_StandardInput_CapitalizeOnlyFirstLetter()
{
    string orig = "this is Brian's test.";
    string result = orig.UpperCaseFirstCharacter();

    Assert.AreEqual("This is Brian's test.", result);
}

2012-06-09 17:56:02

使字符串的第一个字母大写(以最大性能)

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