C#：循环遍历多行字符串
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原文地址: http://stackoverflow.com/questions/1500194/
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C#: Looping through lines of multiline string
提问by flamey
What is a good way to loop through each line of a multiline string without using much more memory (for example without splitting it into an array)?
循环遍历多行字符串的每一行而不使用更多内存（例如不将其拆分为数组）的好方法是什么？
采纳答案by Jon Skeet
I suggest using a combination of StringReaderand my LineReaderclass, which is part of MiscUtilbut also available in this StackOverflow answer- you can easily copy just that class into your own utility project. You'd use it like this:
我建议使用StringReader和 myLineReader类的组合，它是MiscUtil 的一部分，但也可在此 StackOverflow 答案中使用- 您可以轻松地将该类复制到您自己的实用程序项目中。你会像这样使用它：
string text = @"First line
second line
third line";
foreach (string line in new LineReader(() => new StringReader(text)))
{
Console.WriteLine(line);
}
Looping over all the lines in a body of string data (whether that's a file or whatever) is so common that it shouldn't require the calling code to be testing for null etc :) Having said that, if you dowant to do a manual loop, this is the form that I typically prefer over Fredrik's:
循环遍历字符串数据主体中的所有行（无论是文件还是其他任何内容）是如此常见，以至于它不应该要求调用代码测试 null 等:) 话虽如此，如果您确实想做一个手动循环，这是我通常比 Fredrik 更喜欢的形式：
using (StringReader reader = new StringReader(input))
{
string line;
while ((line = reader.ReadLine()) != null)
{
// Do something with the line
}
}
This way you only have to test for nullity once, and you don't have to think about a do/while loop either (which for some reason always takes me more effort to read than a straight while loop).
这样你只需要测试一次无效性，你也不必考虑 do/while 循环（由于某种原因，它总是比直接的 while 循环花费更多的精力来阅读）。
回答by Fredrik M?rk
You can use a StringReaderto read a line at a time:
您可以使用 a 一次StringReader读取一行：
using (StringReader reader = new StringReader(input))
{
string line = string.Empty;
do
{
line = reader.ReadLine();
if (line != null)
{
// do something with the line
}
} while (line != null);
}
回答by tster
from MSDN for StringReader
来自 MSDN 的StringReader
string textReaderText = "TextReader is the abstract base " +
"class of StreamReader and StringReader, which read " +
"characters from streams and strings, respectively.\n\n" +
"Create an instance of TextReader to open a text file " +
"for reading a specified range of characters, or to " +
"create a reader based on an existing stream.\n\n" +
"You can also use an instance of TextReader to read " +
"text from a custom backing store using the same " +
"APIs you would use for a string or a stream.\n\n";
Console.WriteLine("Original text:\n\n{0}", textReaderText);
// From textReaderText, create a continuous paragraph
// with two spaces between each sentence.
string aLine, aParagraph = null;
StringReader strReader = new StringReader(textReaderText);
while(true)
{
aLine = strReader.ReadLine();
if(aLine != null)
{
aParagraph = aParagraph + aLine + " ";
}
else
{
aParagraph = aParagraph + "\n";
break;
}
}
Console.WriteLine("Modified text:\n\n{0}", aParagraph);
回答by palswim
Here's a quick code snippet that will find the first non-empty line in a string:
这是一个快速代码片段，它将找到字符串中的第一个非空行：
string line1;
while (
((line1 = sr.ReadLine()) != null) &&
((line1 = line1.Trim()).Length == 0)
)
{ /* Do nothing - just trying to find first non-empty line*/ }
if(line1 == null){ /* Error - no non-empty lines in string */ }
回答by Niels
I know this has been answered, but I'd like to add my own answer:
我知道这已经得到了回答，但我想添加我自己的答案：
using (var reader = new StringReader(multiLineString))
{
for (string line = reader.ReadLine(); line != null; line = reader.ReadLine())
{
// Do something with the line
}
}
回答by NickG
To update this ancient question for .NET 4, there is now a much neater way:
为了更新 .NET 4 这个古老的问题，现在有一个更简洁的方法：
var lines = File.ReadAllLines(filename);
foreach (string line in lines)
{
Console.WriteLine(line);
}
