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Split one string and put it in two arrays

I'd like to split several strings of a text file into two strings each (example: car;driver). I do not know how to put the first word in array1 and the second word in array2. So I tried with an if query for a semicolon to put every single letter of word1 in array1 and the same with the second word to put them back together to the words later.
But I think it's too complicated what I've done and I am stuck now, lol.
Here I show a piece of my code:
private void BtnShow_Click(object sender, EventArgs e)
{
LibPasswords.Items.Clear();
string path = "passwords.txt";
int counter = 0;
using (FileStream fs = new FileStream(path, FileMode.Open, FileAccess.Read))
using (StreamReader reader = new StreamReader(fs))
{
while (reader.ReadLine() != null)
{
counter++;
}
//for (int i = 0; i < counter; i++)
//{
// var Website = reader.ReadLine().Split(';').Select(x => new String[] { x });
// var Passwort = reader.ReadLine().Split(';').Select(y => new String[] { y });
// LibPasswords.Items.Add(String.Format(table, Website, Passwort));
//}
string[] firstWord = new string[counter];
string[] lastWord = new string[counter];
int i = 0;
int index = 0;
while (reader.Peek() >= 0)
{
string ch = reader.Read().ToString();
if (ch != ";")
{
firstWord[i] = ch;
i++;
}
else
{
index = 1;
}
while (reader.Peek() >= 0)
{
??????????????????????????????????
}
}
}
}
Sorry for my English, it's not my mother tongue.

As you don't know in advance how many lines there are, it is more convenient to use a List<string> instead of a string[]. A List will automatically increase its capacity as needed.
You can use the string.Split method to split the string at the ';' into an array. If the resulting array has the correct number of parts, you can add those parts to the Lists.
List<string> firstWord = new List<string>();
List<string> lastWord = new List<string>();
string fileName = #"C:\temp\SO61715409.txt";
foreach (string line in File.ReadLines(fileName))
{
string[] parts = line.Split(new char[] { ';' });
if (parts.Length == 2)
{
firstWord.Add(parts[0]);
lastWord.Add(parts[1]);
}
}

Use the "new" keyword to create an object instance [duplicate]

This question already has answers here:
What is a NullReferenceException, and how do I fix it?
(27 answers)
Closed 6 years ago.
Is someone able to help me out with the following please, I'm trying to split data from an input file (2 pieces of data per line, separated by either of the delimiters specified in the code below). To do this I have declared the string array 'split input', however when I run the program I get a runtime error (screenshot) with the split input line inside the while loop highlighted in yellow. I can't see what I am doing wrong, I'm copying sample code which seems to be working fine :(
NB - the messageBox line below the yellow is just for my testing to prove the split worked
private int DetermineArraySize(StreamReader inputFile)
{
int count = 0;
while (!inputFile.EndOfStream)
{
inputFile.ReadLine();
count++;
}
return count;
}
private void ReadIntoArray(StreamReader inputFile, string[] gameArray, int[] revArray)
{
string rawInput;
string[] splitInput = new string[2];
int count = 0;
char[] delimiters = {'=', '#',};
while (!inputFile.EndOfStream || count < gameArray.Length)
{
rawInput = inputFile.ReadLine();
{
splitInput = rawInput.Split(delimiters);
MessageBox.Show(splitInput[0] + " // " + splitInput[1]);
count++;
}
}
}
private void rdGameSalesForm_Load(object sender, EventArgs e)
{
StreamReader inputFile = File.OpenText("GameSales.txt"); //Open Input File
int arraySize = DetermineArraySize(inputFile); //Use input file to determine array size
string[] gameTitle = new string[arraySize]; //Declare array for GameTitle
int[] revenue = new int[arraySize]; ///Declare array for Revenue
ReadIntoArray(inputFile, gameTitle, revenue);
Thanks for your help

Just add check on null.
ReadLine Method returns null if the end of the input stream is reached. It is possible because you check !inputFile.EndOfStream or count < gameArray.Length. So in the second condition has a possibility to get null when input filre reading
while (!inputFile.EndOfStream || count < gameArray.Length)
{
rawInput = inputFile.ReadLine();
if(rawInput !=null)
{
splitInput = rawInput.Split(delimiters);
MessageBox.Show(splitInput[0] + " // " + splitInput[1]);
}
}

Check for null instead of end of stream.
while((rawInput = Inputfile.ReadLine()) != null)
{
splitInput = rawInput.Split(delimiters);
MessageBox.Show(...);
}

How to search to search a file for string, display the line containing the string and also the 6 lines preceding it

I am trying to search through a text file for a string, once I have found this string I need to display this line and then also display the 6 preceding lines i.e. which will contain the details about the error message in the string. I have been searching for similar code and have found the following code but it doesn’t meet my requirements, just wondering if it's possible to do this.
Thanks,
John.
private static void Main(string[] args)
{
string cacheline = "";
string line;
System.IO.StreamReader file = new
System.IO.StreamReader(#"D:\Temp\AccessOutlook.txt");
List<string> lines = new List<string>();
while ((line = file.ReadLine()) != null)
{
if (line.Contains("errors"))
{
lines.Add(cacheline);
}
cacheline = line;
}
file.Close();
foreach (var l in lines)
{
Console.WriteLine(l);
}
}
}

This is probably what you want:
static void Main(string[] args)
{
Queue<string> lines = new Queue<string>();
using (var reader = new StreamReader(args[0]))
{
string line;
while ((line = reader.ReadLine()) != null)
{
if (line.Contains("error"))
{
Console.WriteLine("----- ERROR -----");
foreach (var errLine in lines)
Console.WriteLine(errLine);
Console.WriteLine(line);
Console.WriteLine("-----------------");
}
lines.Enqueue(line);
while (lines.Count > 6)
lines.Dequeue();
}
}
}

You can keep caching the lines until you find the line you are looking for:
using(var file = new StreamReader(#"D:\Temp\AccessOutlook.txt"))
{
List<string> lines = new List<string>();
while ((line = file.ReadLine()) != null)
{
if (!line.Contains(myString))
{
lines.Add(line);
}
else
{
Console.WriteLine(string.Join(Environment.NewLine, lines.Concat(new[] { line })));
}
if(lines.Count > 6) lines.RemoveAt(0);
}
}

string filename = "filename"; // Put your own filename here.
string target = "target"; // Put your target string here.
int numLinesToShow = 7;
var lines = File.ReadAllLines(filename);
int index = Array.FindIndex(lines, element => element.Contains(target));
if (index >= 0)
{
int start = Math.Max(0, index - numLinesToShow + 1);
var result = lines.Skip(start).Take(numLinesToShow).ToList();
// Use result.
}

The code below will open the file, search for the line you want, and then write the 6 preceeding lines to the Console.
var lines = File.ReadAllLines(filePath);
int lineIndex;
for (lineIndex = 0; lineIndex < lines.Length - 1; lineIndex++)
{
if (lines[lineIndex] == textToFind)
{
break;
}
}
var startLine = Math.Max(0, lineIndex - 6);
for (int i = startLine; i < lineIndex; i++)
{
Console.WriteLine(lines[i]);
}

Issue with .NET String.Split

I'm attempting to parse a text file containing data that is being used on a remote FTP server. The data is delimited by an equals sign (=) and I'm attempting to load each row in to two columns in a DataGridView. The code I have written works fine except for when an equals character is thrown into the second column's value. When this happens, regardless of specifying the maximum count as being 2. I'd prefer not to change the delimiter if possible.
Here is the code that is being problematic:
dataGrid_FileContents.Rows.Clear();
char delimiter = '=';
StreamReader fileReader = new StreamReader(fileLocation);
String fileData = fileReader.ReadToEnd();
String[] rows = fileData.Split("\n".ToCharArray());
for(int i = 0; i < rows.Length; i++)
{
String str = rows[i];
String[] items = str.Split(new char[] { delimiter }, 1, StringSplitOptions.RemoveEmptyEntries);
if (items.Length == 2)
{
dataGrid_FileContents.Rows.Add(items[0], items[1]);
}
}
fileReader.Close();
And an example of the file being loaded:
boats=123
cats=234-f
cars==1
It works as intended for the first two rows and then ignores the last row as it ends up creating a String[] with 1 element and two String[]s with zero elements.

Try the following. It will capture the value before and after the first '=', correctly parsing the cars==1 scenario.
String[] items = str.Split(new char[] { delimiter }, 2, stringSplitOptions.None);

A different solution, if you want everything after the first equals then you could approach this problem using string.IndexOf
for(int i = 0; i < rows.Length; i++)
{
String str = rows[i];
int pos = str.IndexOf(delimiter);
if (pos != -1)
{
string first = str.Substring(0, pos-1);
string second = str.Substring(pos + 1);
dataGrid_FileContents.Rows.Add(first, second);
}
}

Just read all items delimeted by '=' in row.
Then iterate over items, and check, that item not empty, than use this prepared data to write
here illustrated snippet
http://dotnetfiddle.net/msVho2
and your snippet can be transformed to something like bellow
dataGrid_FileContents.Rows.Clear();
char delimiter = '=';
using(StreamReader fileReader = new StreamReader(fileLocation))
{
string[] data = new string[2];
while(true)
{
string row = fileReader.ReadLine();
if(row == null)
break;
string[] items = row.Split(delimiter);
int data_index = 0;
foreach(string item in items)
{
if(data_index >= data.Length)
{
//TODO: log warning
break;
}
if(!string.IsNullOrWhiteSpace(item))
{
data[data_index++] = item;
}
}
if(data_index < data.Length)
{
//TODO: log error, only 1 item in row
continue;
}
dataGrid_FileContents.Rows.Add(data[0], data[1]);
}
}

Split large string into smaller chunks in c#

I have a large string separated by newline character. This string contains 100 lines. I want to split these line into small chunks say chunk of 20 also based on newline character.
Let's say the string variable is like this,
Line1 This is line2 Line3 is here I am Line4
Now I want to split this large string variable into small chunks of 2. The result should be 2 strings as,
Line1 This is line2
Line3 is here I am Line4
Using Split function, I am not getting the expected results. Please help me in achieving this.
Thanks in advance,
Vijay

The simple approach (Split on Environment.NewLine, then loop and append):
public static List<string> GetStringSegments(string originalString, int linesPerSegment)
{
List<string> segments = new List<string>();
string[] allLines = originalString.Split(new string[] {Environment.NewLine}, StringSplitOptions.RemoveEmptyEntries);
StringBuilder sb = new StringBuilder();
int linesProcessed = 0;
for (int i = 0; i < allLines.Length; i++)
{
sb.AppendLine(allLines[i]);
linesProcessed++;
if (linesProcessed == linesPerSegment
|| i == allLines.Length-1)
{
segments.Add(sb.ToString());
sb.Clear();
inesProcessed = 0;
}
}
return segments;
}
The above approach is slightly inefficient since it requires splitting the string first into individual lines, which creates unnecessary strings. A string of 1000 lines will create an array of 1000 strings. We can improved this if we just scan the string and search for \n:
public static List<string> GetStringSegments(string original, int linesPerSegment)
{
List<string> segments = new List<string>();
int startIndex = 0;
int newLinesEncountered = 0;
for (int i = 0; i < original.Length; i++)
{
if (original[i] == '\n')
{
newLinesEncountered++;
}
if (newLinesEncountered == linesPerSegment
|| i == original.Length - 1)
{
segments.Add(original.Substring(startIndex, (i - startIndex + 1)));
startIndex = i + 1;
newLinesEncountered = 0;
}
}
return segments;
}

You can use something like the batch operator from http://www.make-awesome.com/2010/08/batch-or-partition-a-collection-with-linq
string s = "[YOUR DATA]";
var lines = s.Split(new[]{Environment.NewLine}, StringSplitOptions.RemoveEmptyEntries);
foreach(var batch in lines.Batch(20))
{
foreach(batchLine in batch)
{
Console.Writeline(batchLine);
}
}
static class LinqEx
{
// from http://www.make-awesome.com/2010/08/batch-or-partition-a-collection-with-linq
public static IEnumerable<IEnumerable<T>> Batch<T>(this IEnumerable<T> collection,
int batchSize)
{
List<T> nextbatch = new List<T>(batchSize);
foreach (T item in collection)
{
nextbatch.Add(item);
if (nextbatch.Count == batchSize)
{
yield return nextbatch;
nextbatch = new List<T>(batchSize);
}
}
if (nextbatch.Count > 0)
yield return nextbatch;
}
}

As several people mentioned, using string.Split will split the whole string into memory, which might be an allocation-heavy operation. This is why we have the TextReader class and its descendants, which should provide better memory performance, and might also be clearer, logically:
using (var reader = new StringReader(myString))
{
do
{
StringBuilder newString = null;
StringWriter newStringWriter = null;
if (lineCounter % 20 == 0)
{
newString = new StringBuilder();
newStringWriter = new StringWriter(newString);
newStringCollection.Add(newString);
}
string line = reader.ReadLine();
if (!string.isNullOrEmpty(line))
{
newStringWriter.WriteLine(line);
lineCounter++;
}
}
while (line != null)
}
We're using the StringReader to read our big string, one line at a time. And the corresponding StringWriter writes those lines to the new string, one line a time. After every 20 lines, we start a new StringBuilder (and the appropriate StringWriter wrapper).

split the strings by newline.
Then merge/fetch the number of strings together while using the strings.

string s = "Line1\nThis is line2 \nLine3 is here\nI am Line4";
string [] str = s.split('\n');
List<String> str1 = new List<String>();
for(int i=0; i<str.Length; i+=2)
{
string ss = str[i];
if(i+1 <str.Length)
ss += '\n' + str[i+1];
str1.Add(ss);
}
str = str1.ToArray();
If condition has been checked inside loop because may be the length of str is odd

var strAray = myLongString.Split('\n').ToList();
var skip=0;
var take=20;
var chunk = strAray.Skip(skip).Take(take).ToList();
While(chunk.Count >0)
{
foreach(var line in chunk)
{
// use line string
}
skip++;
chunk = strAray.Skip(skip).Take(take).ToList()
}