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。
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);
}
使用string.Create()并在方法中避免使用throw关键字(是的，您没有看错)，我们可以进一步采用Marcell的答案。此外，我的方法处理任意长度的字符串(例如，几兆字节的文本)。
public static string L33t(this string s)
{
static void ThrowError() => throw new ArgumentException("There is no first letter");
if (string.IsNullOrEmpty(s))
ThrowError(); // No "throw" keyword to avoid costly IL
return string.Create(s.Length, s, (chars, state) =>
{
state.AsSpan().CopyTo(chars); // No slicing to save some CPU cycles
chars[0] = char.ToUpper(chars[0]);
});
}
性能
下面是在。net Core 3.1.7 64位上运行的基准测试的数据。我添加了一个更长的字符串，以精确计算额外拷贝的成本。
| Method |
Data |
Mean |
Error |
StdDev |
Median |
| L33t |
red |
8.545 ns |
0.4612 ns |
1.3308 ns |
8.075 ns |
| Marcell |
red |
9.153 ns |
0.3377 ns |
0.9471 ns |
8.946 ns |
| L33t |
red house |
7.715 ns |
0.1741 ns |
0.4618 ns |
7.793 ns |
| Marcell |
red house |
10.537 ns |
0.5002 ns |
1.4351 ns |
10.377 ns |
| L33t |
red r(...)house [89] |
11.121 ns |
0.6774 ns |
1.9106 ns |
10.612 ns |
| Marcell |
red r(...)house [89] |
16.739 ns |
0.4468 ns |
1.3033 ns |
16.853 ns |
完整的测试代码
using System;
using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;
namespace CorePerformanceTest
{
class Program
{
static void Main(string[] args)
{
var summary = BenchmarkRunner.Run<StringUpperTest>();
}
}
public class StringUpperTest
{
[Params("red", "red house", "red red red red red red red red red red red red red red red red red red red red red house")]
public string Data;
[Benchmark]
public string Marcell() => Data.Marcell();
[Benchmark]
public string L33t() => Data.L33t();
}
internal static class StringExtensions
{
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);
}
public static string L33t(this string s)
{
static void ThrowError() => throw new ArgumentException("There is no first letter");
if (string.IsNullOrEmpty(s))
ThrowError(); // IMPORTANT: Do not "throw" here!
return string.Create(s.Length, s, (chars, state) =>
{
state.AsSpan().CopyTo(chars);
chars[0] = char.ToUpper(chars[0]);
});
}
}
}
如果你能让它更快，请告诉我!
