C＃：通过多行字符串循环循环

Question

什么是循环多行字符串的每一行而不使用更多内存的好方法（例如，不需要将其拆分成数组）？

Answer 1

我建议使用的StringReader组合和我LineReader类，这是部分的MiscUtil，但也可在this StackOverflow answer - 你可以很容易地将该类复制到您自己的实用程序项目。你会使用这样的：

string text = @"First line 
second line 
third line"; 

foreach (string line in new LineReader(() => new StringReader(text))) 
{ 
    Console.WriteLine(line); 
} 

循环遍历字符串数据的身体所有行（不管是文件或其他）是很常见的，它不应该要求调用代码是用于测试空等:)说了这么多，如果你做想做一个手动循环，这是我通常更喜欢弗雷德里克的形式：

using (StringReader reader = new StringReader(input)) 
{ 
    string line; 
    while ((line = reader.ReadLine()) != null) 
    { 
     // Do something with the line 
    } 
} 

这种方式，你只需要测试无效一次，你不必考虑一个do/while循环（由于某种原因，它总是需要我花更多的努力来阅读，而不是直接的while循环）。

Answer 2

您可以使用StringReader在一次读取一行：

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); 
} 

Answer 3

从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); 

Answer 4

下面是一个简单的代码片段，会发现在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 */ } 

Answer 5

我知道这已经回答了，但我想补充我自己的答案：

using (var reader = new StringReader(multiLineString)) 
{ 
    for (string line = reader.ReadLine(); line != null; line = reader.ReadLine()) 
    { 
     // Do something with the line 
    } 
}