C Looping through lines of multiline string

Question

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

User · Answer

Here s a quick code snippet that will find the first non-empty line in a string   string line1  while         line1   sr ReadLine       null   amp  amp        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

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You can use a StringReader to read a line at a time   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

User · Answer

To update this ancient question for  NET 4  there is now a much neater way    var lines   File ReadAllLines filename    foreach  string line in lines        Console WriteLine line

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I know this has been answered  but I d like to add my own answer   using  var reader   new StringReader multiLineString         for  string line   reader ReadLine    line    null  line   reader ReadLine                     Do something with the line

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Try using String Split Method  string text     quot First line second line third line quot    foreach  string line in text Split   n             do something

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I suggest using a combination of StringReader and my LineReader class  which is part of MiscUtil but also available in this StackOverflow answer - you can easily copy just that class into your own utility project  You d use it like this   string text     First line second line third line    foreach  string line in new LineReader      gt  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 do want to do a manual loop  this is the form that I typically prefer over Fredrik s   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

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from MSDN for 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

User · Answer

Sometimes I think we can overcomplicate the solution just to avoid repeating one line of code  This is the reason I landed on this question in the first place  After thinking about it for a bit I came to the conclusion that the simplest solution is to repeat the ReadLine before and inside the loop  using  var stringReader   new StringReader input         var line   await stringReader ReadLineAsync         while  line    null                   do something         line   await stringReader ReadLineAsync             I realize this might be considered to not follow the DRY principle  but I think it s worth considering given the simplicity

[c#] C#: Looping through lines of multiline string

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