Related
That code makes filter on the files with the regular expression, and to shape the results. But how can I get a line number of each matches in the file?
I have no idea how to do it...
Please help me
class QueryWithRegEx
enter code here
IEnumerable<System.IO.FileInfo> fileList = GetFiles(startFolder);
System.Text.RegularExpressions.Regex searchTerm =
new System.Text.RegularExpressions.Regex(#"Visual (Basic|C#|C\+\+|Studio)");
var queryMatchingFiles =
from file in fileList
where file.Extension == ".htm"
let fileText = System.IO.File.ReadAllText(file.FullName)
let matches = searchTerm.Matches(fileText)
where matches.Count > 0
select new
{
name = file.FullName,
matchedValues = from System.Text.RegularExpressions.Match match in matches
select match.Value
};
Console.WriteLine("The term \"{0}\" was found in:", searchTerm.ToString());
foreach (var v in queryMatchingFiles)
{
string s = v.name.Substring(startFolder.Length - 1);
Console.WriteLine(s);
foreach (var v2 in v.matchedValues)
{
Console.WriteLine(" " + v2);
}
}
Console.WriteLine("Press any key to exit");
Console.ReadKey();
}
static IEnumerable<System.IO.FileInfo> GetFiles(string path)
{
...}
Give this a go:
var queryMatchingFiles =
from file in Directory.GetFiles(startFolder)
let fi = new FileInfo(file)
where fi.Extension == ".htm"
from line in File.ReadLines(file).Select((text, index) => (text, index))
let match = searchTerm.Match(line.text)
where match.Success
select new
{
name = file,
line = line.text,
number = line.index + 1
};
You can Understand from this example:
Read lines number 3 from string
string line = File.ReadLines(FileName).Skip(14).Take(1).First();
Read text from a certain line number from string
string GetLine(string text, int lineNo)
{
string[] lines = text.Replace("\r","").Split('\n');
return lines.Length >= lineNo ? lines[lineNo-1] : null;
}
Retrieving the line number from a Regex match can be tricky, I'd use the following approach:
private static void FindMatches(string startFolder)
{
var searchTerm = new Regex(#"Visual (Basic|C#|C\+\+|Studio)");
foreach (var file in Directory.GetFiles(startFolder, "*.htm"))
{
using (var reader = new StreamReader(file))
{
int lineNumber = 1;
string lineText;
while ((lineText = reader.ReadLine()) != null)
{
foreach (var match in searchTerm.Matches(lineText).Cast<Match>())
{
Console.WriteLine($"Match found: <{match.Value}> in file <{file}>, line <{lineNumber}>");
}
lineNumber++;
}
}
}
}
I'm trying to read a text file to two string arrays. Array1 is to be all the odd lines, array2 all the even lines. I then add all the items of array1 to a combobox and when that is selected, or as it gets typed, outputs array2 to a textbox.
So far, I have tried a few methods from here, but the big issue seems to be creating the arrays. I tried to get help here before, but the answers didn't actually answer my question. They must be arrays, not lists (which I tried and worked well). I am really confused by this whole thing and my attempted code is now rubbish:
private void ReadFile(string filePath, string customerPhone, string customerName)
{
string line = string.Empty;
var fileSR = new StreamReader(filePath);
bool number = true;
while((line = fileSR.ReadLine()) != null)
{
if (number)
{
customerPhone(line);
number = false;
}
else
{
customerName(line);
number = true;
}
}
fileSR.Close();
}
I'm losing confidence in this whole process, but I need to find a way to make it work, then I can learn why it does.
You are almost there, just use the List<string>.
private void ReadFile(string filePath, string customerPhone, string customerName)
{
string line = string.Empty;
using (var fileSR = new StreamReader(filePath))
{
bool number = true;
List<string> customerPhone = new List<string>();
List<string> customerName = new List<string>();
while((line = fileSR.ReadLine()) != null)
{
if (number)
{
customerPhone.Add(line);
number = false;
}
else
{
customerName.Add(line);
number = true;
}
}
fileSR.Close();
}
}
If you are interested only in Arrays, you could simply call customerName.ToArray() to convert it to an array.
Linq Solution
Alternatively you could use Linq and do this.
var bothArrays = File.ReadLines("filepath") // Read All lines
.Select((line,index) => new {line, index+1}) // index each line
.GroupBy(x=> x/2) // Convert into two groups
.SelectMany(x=> x.Select(s=>s.line).ToArray()) // Convert it to array
.ToArray();
You should use collections to return data, say IList<String>:
private static void ReadFile(String filePath,
IList<String> oddLines,
IList<String> evenLines) {
oddLines.Clear();
evenLines.Clear();
int index = 1; //TODO: start with 0 or with 1
foreach (String line in File.ReadLines(filePath)) {
if (index % 2 == 0)
evenLines.Add(line);
else
oddLines.Add(line);
index += 1;
}
}
using
List<String> names = new List<String>();
List<String> phones = new List<String>();
ReadFile(#"C:\MyDate.txt", names, phones);
// If you want array representation
String[] myNames = names.ToArray();
String[] myPhones = phones.ToArray();
// Let's print out names
Console.Write(String.Join(Envrironment.NewLine, names));
Please, notice, that using File.ReadLines usually more convenient than StreamReader which should be wrapped in using:
// foreach (String line in File.ReadLines(filePath)) equals to
using (var fileSR = new StreamReader(filePath)) {
while ((line = fileSR.ReadLine()) != null) {
...
}
}
This worked! I have these class level strings:
string cFileName = "customer.txt";
string[] cName = new string[0];
string[] cPhone = new string[0];
And then this in the Window Loaded event, but could be used in it's own method:
private void Window_Loaded_1(object sender, RoutedEventArgs e)
{
//read file on start
int counter = 0;
string line;
StreamReader custSR = new StreamReader(cFileName);
line = custSR.ReadLine();
while (custSR.Peek() != -1)
{
Array.Resize(ref cPhone, cPhone.Length + 1);
cPhone[cPhone.Length - 1] = line;
counter++;
line = custSR.ReadLine();
Array.Resize(ref cName, cName.Length + 1);
cName[cName.Length - 1] = line;
counter++;
line = custSR.ReadLine();
phoneComboBox.Items.Add(cPhone[cPhone.Length - 1]);
}
custSR.Close();
//focus when program starts
phoneComboBox.Focus();
}
Is there a default/official/recommended way to parse CSV files in C#? I don't want to roll my own parser.
Also, I've seen instances of people using ODBC/OLE DB to read CSV via the Text driver, and a lot of people discourage this due to its "drawbacks." What are these drawbacks?
Ideally, I'm looking for a way through which I can read the CSV by column name, using the first record as the header / field names. Some of the answers given are correct but work to basically deserialize the file into classes.
A CSV parser is now a part of .NET Framework.
Add a reference to Microsoft.VisualBasic.dll (works fine in C#, don't mind the name)
using (TextFieldParser parser = new TextFieldParser(#"c:\temp\test.csv"))
{
parser.TextFieldType = FieldType.Delimited;
parser.SetDelimiters(",");
while (!parser.EndOfData)
{
//Process row
string[] fields = parser.ReadFields();
foreach (string field in fields)
{
//TODO: Process field
}
}
}
The docs are here - TextFieldParser Class
P.S. If you need a CSV exporter, try CsvExport (discl: I'm one of the contributors)
CsvHelper (a library I maintain) will read a CSV file into custom objects.
using (var reader = new StreamReader("path\\to\\file.csv"))
using (var csv = new CsvReader(reader, CultureInfo.InvariantCulture))
{
var records = csv.GetRecords<Foo>();
}
Sometimes you don't own the objects you're trying to read into. In this case, you can use fluent mapping because you can't put attributes on the class.
public sealed class MyCustomObjectMap : CsvClassMap<MyCustomObject>
{
public MyCustomObjectMap()
{
Map( m => m.Property1 ).Name( "Column Name" );
Map( m => m.Property2 ).Index( 4 );
Map( m => m.Property3 ).Ignore();
Map( m => m.Property4 ).TypeConverter<MySpecialTypeConverter>();
}
}
Let a library handle all the nitty-gritty details for you! :-)
Check out FileHelpers and stay DRY - Don't Repeat Yourself - no need to re-invent the wheel a gazillionth time....
You basically just need to define that shape of your data - the fields in your individual line in the CSV - by means of a public class (and so well-thought out attributes like default values, replacements for NULL values and so forth), point the FileHelpers engine at a file, and bingo - you get back all the entries from that file. One simple operation - great performance!
In a business application, i use the Open Source project on codeproject.com, CSVReader.
It works well, and has good performance. There is some benchmarking on the link i provided.
A simple example, copied from the project page:
using (CsvReader csv = new CsvReader(new StreamReader("data.csv"), true))
{
int fieldCount = csv.FieldCount;
string[] headers = csv.GetFieldHeaders();
while (csv.ReadNextRecord())
{
for (int i = 0; i < fieldCount; i++)
Console.Write(string.Format("{0} = {1};", headers[i], csv[i]));
Console.WriteLine();
}
}
As you can see, it's very easy to work with.
I know its a bit late but just found a library Microsoft.VisualBasic.FileIO which has TextFieldParser class to process csv files.
Here is a helper class I use often, in case any one ever comes back to this thread (I wanted to share it).
I use this for the simplicity of porting it into projects ready to use:
public class CSVHelper : List<string[]>
{
protected string csv = string.Empty;
protected string separator = ",";
public CSVHelper(string csv, string separator = "\",\"")
{
this.csv = csv;
this.separator = separator;
foreach (string line in Regex.Split(csv, System.Environment.NewLine).ToList().Where(s => !string.IsNullOrEmpty(s)))
{
string[] values = Regex.Split(line, separator);
for (int i = 0; i < values.Length; i++)
{
//Trim values
values[i] = values[i].Trim('\"');
}
this.Add(values);
}
}
}
And use it like:
public List<Person> GetPeople(string csvContent)
{
List<Person> people = new List<Person>();
CSVHelper csv = new CSVHelper(csvContent);
foreach(string[] line in csv)
{
Person person = new Person();
person.Name = line[0];
person.TelephoneNo = line[1];
people.Add(person);
}
return people;
}
[Updated csv helper: bug fixed where the last new line character created a new line]
If you need only reading csv files then I recommend this library: A Fast CSV Reader
If you also need to generate csv files then use this one: FileHelpers
Both of them are free and opensource.
This solution is using the official Microsoft.VisualBasic assembly to parse CSV.
Advantages:
delimiter escaping
ignores Header
trim spaces
ignore comments
Code:
using Microsoft.VisualBasic.FileIO;
public static List<List<string>> ParseCSV (string csv)
{
List<List<string>> result = new List<List<string>>();
// To use the TextFieldParser a reference to the Microsoft.VisualBasic assembly has to be added to the project.
using (TextFieldParser parser = new TextFieldParser(new StringReader(csv)))
{
parser.CommentTokens = new string[] { "#" };
parser.SetDelimiters(new string[] { ";" });
parser.HasFieldsEnclosedInQuotes = true;
// Skip over header line.
//parser.ReadLine();
while (!parser.EndOfData)
{
var values = new List<string>();
var readFields = parser.ReadFields();
if (readFields != null)
values.AddRange(readFields);
result.Add(values);
}
}
return result;
}
I have written TinyCsvParser for .NET, which is one of the fastest .NET parsers around and highly configurable to parse almost any CSV format.
It is released under MIT License:
https://github.com/bytefish/TinyCsvParser
You can use NuGet to install it. Run the following command in the Package Manager Console.
PM> Install-Package TinyCsvParser
Usage
Imagine we have list of Persons in a CSV file persons.csv with their first name, last name and birthdate.
FirstName;LastName;BirthDate
Philipp;Wagner;1986/05/12
Max;Musterman;2014/01/02
The corresponding domain model in our system might look like this.
private class Person
{
public string FirstName { get; set; }
public string LastName { get; set; }
public DateTime BirthDate { get; set; }
}
When using TinyCsvParser you have to define the mapping between the columns in the CSV data and the property in you domain model.
private class CsvPersonMapping : CsvMapping<Person>
{
public CsvPersonMapping()
: base()
{
MapProperty(0, x => x.FirstName);
MapProperty(1, x => x.LastName);
MapProperty(2, x => x.BirthDate);
}
}
And then we can use the mapping to parse the CSV data with a CsvParser.
namespace TinyCsvParser.Test
{
[TestFixture]
public class TinyCsvParserTest
{
[Test]
public void TinyCsvTest()
{
CsvParserOptions csvParserOptions = new CsvParserOptions(true, new[] { ';' });
CsvPersonMapping csvMapper = new CsvPersonMapping();
CsvParser<Person> csvParser = new CsvParser<Person>(csvParserOptions, csvMapper);
var result = csvParser
.ReadFromFile(#"persons.csv", Encoding.ASCII)
.ToList();
Assert.AreEqual(2, result.Count);
Assert.IsTrue(result.All(x => x.IsValid));
Assert.AreEqual("Philipp", result[0].Result.FirstName);
Assert.AreEqual("Wagner", result[0].Result.LastName);
Assert.AreEqual(1986, result[0].Result.BirthDate.Year);
Assert.AreEqual(5, result[0].Result.BirthDate.Month);
Assert.AreEqual(12, result[0].Result.BirthDate.Day);
Assert.AreEqual("Max", result[1].Result.FirstName);
Assert.AreEqual("Mustermann", result[1].Result.LastName);
Assert.AreEqual(2014, result[1].Result.BirthDate.Year);
Assert.AreEqual(1, result[1].Result.BirthDate.Month);
Assert.AreEqual(1, result[1].Result.BirthDate.Day);
}
}
}
User Guide
A full User Guide is available at:
http://bytefish.github.io/TinyCsvParser/
Here is a short and simple solution.
using (TextFieldParser parser = new TextFieldParser(outputLocation))
{
parser.TextFieldType = FieldType.Delimited;
parser.SetDelimiters(",");
string[] headers = parser.ReadLine().Split(',');
foreach (string header in headers)
{
dataTable.Columns.Add(header);
}
while (!parser.EndOfData)
{
string[] fields = parser.ReadFields();
dataTable.Rows.Add(fields);
}
}
Here is my KISS implementation...
using System;
using System.Collections.Generic;
using System.Text;
class CsvParser
{
public static List<string> Parse(string line)
{
const char escapeChar = '"';
const char splitChar = ',';
bool inEscape = false;
bool priorEscape = false;
List<string> result = new List<string>();
StringBuilder sb = new StringBuilder();
for (int i = 0; i < line.Length; i++)
{
char c = line[i];
switch (c)
{
case escapeChar:
if (!inEscape)
inEscape = true;
else
{
if (!priorEscape)
{
if (i + 1 < line.Length && line[i + 1] == escapeChar)
priorEscape = true;
else
inEscape = false;
}
else
{
sb.Append(c);
priorEscape = false;
}
}
break;
case splitChar:
if (inEscape) //if in escape
sb.Append(c);
else
{
result.Add(sb.ToString());
sb.Length = 0;
}
break;
default:
sb.Append(c);
break;
}
}
if (sb.Length > 0)
result.Add(sb.ToString());
return result;
}
}
Some time ago I had wrote simple class for CSV read/write based on Microsoft.VisualBasic library. Using this simple class you will be able to work with CSV like with 2 dimensions array. You can find my class by the following link: https://github.com/ukushu/DataExporter
Simple example of usage:
Csv csv = new Csv("\t");//delimiter symbol
csv.FileOpen("c:\\file1.csv");
var row1Cell6Value = csv.Rows[0][5];
csv.AddRow("asdf","asdffffff","5")
csv.FileSave("c:\\file2.csv");
For reading header only you need is to read csv.Rows[0] cells :)
This code reads csv to DataTable:
public static DataTable ReadCsv(string path)
{
DataTable result = new DataTable("SomeData");
using (TextFieldParser parser = new TextFieldParser(path))
{
parser.TextFieldType = FieldType.Delimited;
parser.SetDelimiters(",");
bool isFirstRow = true;
//IList<string> headers = new List<string>();
while (!parser.EndOfData)
{
string[] fields = parser.ReadFields();
if (isFirstRow)
{
foreach (string field in fields)
{
result.Columns.Add(new DataColumn(field, typeof(string)));
}
isFirstRow = false;
}
else
{
int i = 0;
DataRow row = result.NewRow();
foreach (string field in fields)
{
row[i++] = field;
}
result.Rows.Add(row);
}
}
}
return result;
}
Single source file solution for straightforward parsing needs, useful. Deals with all the nasty edge cases. Such as new line normalization and handling new lines in quoted string literals. Your welcome!
If you CSV file has a header you just read out the column names (and compute column indexes) from the first row. Simple as that.
Note that Dump is a LINQPad method, you might want to remove that if you are not using LINQPad.
void Main()
{
var file1 = "a,b,c\r\nx,y,z";
CSV.ParseText(file1).Dump();
var file2 = "a,\"b\",c\r\nx,\"y,z\"";
CSV.ParseText(file2).Dump();
var file3 = "a,\"b\",c\r\nx,\"y\r\nz\"";
CSV.ParseText(file3).Dump();
var file4 = "\"\"\"\"";
CSV.ParseText(file4).Dump();
}
static class CSV
{
public struct Record
{
public readonly string[] Row;
public string this[int index] => Row[index];
public Record(string[] row)
{
Row = row;
}
}
public static List<Record> ParseText(string text)
{
return Parse(new StringReader(text));
}
public static List<Record> ParseFile(string fn)
{
using (var reader = File.OpenText(fn))
{
return Parse(reader);
}
}
public static List<Record> Parse(TextReader reader)
{
var data = new List<Record>();
var col = new StringBuilder();
var row = new List<string>();
for (; ; )
{
var ln = reader.ReadLine();
if (ln == null) break;
if (Tokenize(ln, col, row))
{
data.Add(new Record(row.ToArray()));
row.Clear();
}
}
return data;
}
public static bool Tokenize(string s, StringBuilder col, List<string> row)
{
int i = 0;
if (col.Length > 0)
{
col.AppendLine(); // continuation
if (!TokenizeQuote(s, ref i, col, row))
{
return false;
}
}
while (i < s.Length)
{
var ch = s[i];
if (ch == ',')
{
row.Add(col.ToString().Trim());
col.Length = 0;
i++;
}
else if (ch == '"')
{
i++;
if (!TokenizeQuote(s, ref i, col, row))
{
return false;
}
}
else
{
col.Append(ch);
i++;
}
}
if (col.Length > 0)
{
row.Add(col.ToString().Trim());
col.Length = 0;
}
return true;
}
public static bool TokenizeQuote(string s, ref int i, StringBuilder col, List<string> row)
{
while (i < s.Length)
{
var ch = s[i];
if (ch == '"')
{
// escape sequence
if (i + 1 < s.Length && s[i + 1] == '"')
{
col.Append('"');
i++;
i++;
continue;
}
i++;
return true;
}
else
{
col.Append(ch);
i++;
}
}
return false;
}
}
Another one to this list, Cinchoo ETL - an open source library to read and write multiple file formats (CSV, flat file, Xml, JSON etc)
Sample below shows how to read CSV file quickly (No POCO object required)
string csv = #"Id, Name
1, Carl
2, Tom
3, Mark";
using (var p = ChoCSVReader.LoadText(csv)
.WithFirstLineHeader()
)
{
foreach (var rec in p)
{
Console.WriteLine($"Id: {rec.Id}");
Console.WriteLine($"Name: {rec.Name}");
}
}
Sample below shows how to read CSV file using POCO object
public partial class EmployeeRec
{
public int Id { get; set; }
public string Name { get; set; }
}
static void CSVTest()
{
string csv = #"Id, Name
1, Carl
2, Tom
3, Mark";
using (var p = ChoCSVReader<EmployeeRec>.LoadText(csv)
.WithFirstLineHeader()
)
{
foreach (var rec in p)
{
Console.WriteLine($"Id: {rec.Id}");
Console.WriteLine($"Name: {rec.Name}");
}
}
}
Please check out articles at CodeProject on how to use it.
This parser supports nested commas and quotes in a column:
static class CSVParser
{
public static string[] ParseLine(string line)
{
List<string> cols = new List<string>();
string value = null;
for(int i = 0; i < line.Length; i++)
{
switch(line[i])
{
case ',':
cols.Add(value);
value = null;
if(i == line.Length - 1)
{// It ends with comma
cols.Add(null);
}
break;
case '"':
cols.Add(ParseEnclosedColumn(line, ref i));
i++;
break;
default:
value += line[i];
if (i == line.Length - 1)
{// Last character
cols.Add(value);
}
break;
}
}
return cols.ToArray();
}//ParseLine
static string ParseEnclosedColumn(string line, ref int index)
{// Example: "b"",bb"
string value = null;
int numberQuotes = 1;
int index2 = index;
for (int i = index + 1; i < line.Length; i++)
{
index2 = i;
switch (line[i])
{
case '"':
numberQuotes++;
if (numberQuotes % 2 == 0)
{
if (i < line.Length - 1 && line[i + 1] == ',')
{
index = i;
return value;
}
}
else if (i > index + 1 && line[i - 1] == '"')
{
value += '"';
}
break;
default:
value += line[i];
break;
}
}
index = index2;
return value;
}//ParseEnclosedColumn
}//class CSVParser
Based on unlimit's post on How to properly split a CSV using C# split() function? :
string[] tokens = System.Text.RegularExpressions.Regex.Split(paramString, ",");
NOTE: this doesn't handle escaped / nested commas, etc., and therefore is only suitable for certain simple CSV lists.
If anyone wants a snippet they can plop into their code without having to bind a library or download a package. Here is a version I wrote:
public static string FormatCSV(List<string> parts)
{
string result = "";
foreach (string s in parts)
{
if (result.Length > 0)
{
result += ",";
if (s.Length == 0)
continue;
}
if (s.Length > 0)
{
result += "\"" + s.Replace("\"", "\"\"") + "\"";
}
else
{
// cannot output double quotes since its considered an escape for a quote
result += ",";
}
}
return result;
}
enum CSVMode
{
CLOSED = 0,
OPENED_RAW = 1,
OPENED_QUOTE = 2
}
public static List<string> ParseCSV(string input)
{
List<string> results;
CSVMode mode;
char[] letters;
string content;
mode = CSVMode.CLOSED;
content = "";
results = new List<string>();
letters = input.ToCharArray();
for (int i = 0; i < letters.Length; i++)
{
char letter = letters[i];
char nextLetter = '\0';
if (i < letters.Length - 1)
nextLetter = letters[i + 1];
// If its a quote character
if (letter == '"')
{
// If that next letter is a quote
if (nextLetter == '"' && mode == CSVMode.OPENED_QUOTE)
{
// Then this quote is escaped and should be added to the content
content += letter;
// Skip the escape character
i++;
continue;
}
else
{
// otherwise its not an escaped quote and is an opening or closing one
// Character is skipped
// If it was open, then close it
if (mode == CSVMode.OPENED_QUOTE)
{
results.Add(content);
// reset the content
content = "";
mode = CSVMode.CLOSED;
// If there is a next letter available
if (nextLetter != '\0')
{
// If it is a comma
if (nextLetter == ',')
{
i++;
continue;
}
else
{
throw new Exception("Expected comma. Found: " + nextLetter);
}
}
}
else if (mode == CSVMode.OPENED_RAW)
{
// If it was opened raw, then just add the quote
content += letter;
}
else if (mode == CSVMode.CLOSED)
{
// Otherwise open it as a quote
mode = CSVMode.OPENED_QUOTE;
}
}
}
// If its a comma seperator
else if (letter == ',')
{
// If in quote mode
if (mode == CSVMode.OPENED_QUOTE)
{
// Just read it
content += letter;
}
// If raw, then close the content
else if (mode == CSVMode.OPENED_RAW)
{
results.Add(content);
content = "";
mode = CSVMode.CLOSED;
}
// If it was closed, then open it raw
else if (mode == CSVMode.CLOSED)
{
mode = CSVMode.OPENED_RAW;
results.Add(content);
content = "";
}
}
else
{
// If opened quote, just read it
if (mode == CSVMode.OPENED_QUOTE)
{
content += letter;
}
// If opened raw, then read it
else if (mode == CSVMode.OPENED_RAW)
{
content += letter;
}
// It closed, then open raw
else if (mode == CSVMode.CLOSED)
{
mode = CSVMode.OPENED_RAW;
content += letter;
}
}
}
// If it was still reading when the buffer finished
if (mode != CSVMode.CLOSED)
{
results.Add(content);
}
return results;
}
For smaller input CSV data LINQ is fully enough.
For example for the following CSV file content:
schema_name,description,utype
"IX_HE","High-Energy data","x"
"III_spectro","Spectrosopic data","d"
"VI_misc","Miscellaneous","f"
"vcds1","Catalogs only available in CDS","d"
"J_other","Publications from other journals","b"
when we read the whole content into single string called data, then
using System;
using System.IO;
using System.Linq;
var data = File.ReadAllText(Path2CSV);
// helper split characters
var newline = Environment.NewLine.ToCharArray();
var comma = ",".ToCharArray();
var quote = "\"".ToCharArray();
// split input string data to lines
var lines = data.Split(newline);
// first line is header, take the header fields
foreach (var col in lines.First().Split(comma)) {
// do something with "col"
}
// we skip the first line, all the rest are real data lines/fields
foreach (var line in lines.Skip(1)) {
// first we split the data line by comma character
// next we remove double qoutes from each splitted element using Trim()
// finally we make an array
var fields = line.Split(comma)
.Select(_ => { _ = _.Trim(quote); return _; })
.ToArray();
// do something with the "fields" array
}
Is there a default/official/recommended way to parse CSV files in C#? I don't want to roll my own parser.
Also, I've seen instances of people using ODBC/OLE DB to read CSV via the Text driver, and a lot of people discourage this due to its "drawbacks." What are these drawbacks?
Ideally, I'm looking for a way through which I can read the CSV by column name, using the first record as the header / field names. Some of the answers given are correct but work to basically deserialize the file into classes.
A CSV parser is now a part of .NET Framework.
Add a reference to Microsoft.VisualBasic.dll (works fine in C#, don't mind the name)
using (TextFieldParser parser = new TextFieldParser(#"c:\temp\test.csv"))
{
parser.TextFieldType = FieldType.Delimited;
parser.SetDelimiters(",");
while (!parser.EndOfData)
{
//Process row
string[] fields = parser.ReadFields();
foreach (string field in fields)
{
//TODO: Process field
}
}
}
The docs are here - TextFieldParser Class
P.S. If you need a CSV exporter, try CsvExport (discl: I'm one of the contributors)
CsvHelper (a library I maintain) will read a CSV file into custom objects.
using (var reader = new StreamReader("path\\to\\file.csv"))
using (var csv = new CsvReader(reader, CultureInfo.InvariantCulture))
{
var records = csv.GetRecords<Foo>();
}
Sometimes you don't own the objects you're trying to read into. In this case, you can use fluent mapping because you can't put attributes on the class.
public sealed class MyCustomObjectMap : CsvClassMap<MyCustomObject>
{
public MyCustomObjectMap()
{
Map( m => m.Property1 ).Name( "Column Name" );
Map( m => m.Property2 ).Index( 4 );
Map( m => m.Property3 ).Ignore();
Map( m => m.Property4 ).TypeConverter<MySpecialTypeConverter>();
}
}
Let a library handle all the nitty-gritty details for you! :-)
Check out FileHelpers and stay DRY - Don't Repeat Yourself - no need to re-invent the wheel a gazillionth time....
You basically just need to define that shape of your data - the fields in your individual line in the CSV - by means of a public class (and so well-thought out attributes like default values, replacements for NULL values and so forth), point the FileHelpers engine at a file, and bingo - you get back all the entries from that file. One simple operation - great performance!
In a business application, i use the Open Source project on codeproject.com, CSVReader.
It works well, and has good performance. There is some benchmarking on the link i provided.
A simple example, copied from the project page:
using (CsvReader csv = new CsvReader(new StreamReader("data.csv"), true))
{
int fieldCount = csv.FieldCount;
string[] headers = csv.GetFieldHeaders();
while (csv.ReadNextRecord())
{
for (int i = 0; i < fieldCount; i++)
Console.Write(string.Format("{0} = {1};", headers[i], csv[i]));
Console.WriteLine();
}
}
As you can see, it's very easy to work with.
I know its a bit late but just found a library Microsoft.VisualBasic.FileIO which has TextFieldParser class to process csv files.
Here is a helper class I use often, in case any one ever comes back to this thread (I wanted to share it).
I use this for the simplicity of porting it into projects ready to use:
public class CSVHelper : List<string[]>
{
protected string csv = string.Empty;
protected string separator = ",";
public CSVHelper(string csv, string separator = "\",\"")
{
this.csv = csv;
this.separator = separator;
foreach (string line in Regex.Split(csv, System.Environment.NewLine).ToList().Where(s => !string.IsNullOrEmpty(s)))
{
string[] values = Regex.Split(line, separator);
for (int i = 0; i < values.Length; i++)
{
//Trim values
values[i] = values[i].Trim('\"');
}
this.Add(values);
}
}
}
And use it like:
public List<Person> GetPeople(string csvContent)
{
List<Person> people = new List<Person>();
CSVHelper csv = new CSVHelper(csvContent);
foreach(string[] line in csv)
{
Person person = new Person();
person.Name = line[0];
person.TelephoneNo = line[1];
people.Add(person);
}
return people;
}
[Updated csv helper: bug fixed where the last new line character created a new line]
If you need only reading csv files then I recommend this library: A Fast CSV Reader
If you also need to generate csv files then use this one: FileHelpers
Both of them are free and opensource.
This solution is using the official Microsoft.VisualBasic assembly to parse CSV.
Advantages:
delimiter escaping
ignores Header
trim spaces
ignore comments
Code:
using Microsoft.VisualBasic.FileIO;
public static List<List<string>> ParseCSV (string csv)
{
List<List<string>> result = new List<List<string>>();
// To use the TextFieldParser a reference to the Microsoft.VisualBasic assembly has to be added to the project.
using (TextFieldParser parser = new TextFieldParser(new StringReader(csv)))
{
parser.CommentTokens = new string[] { "#" };
parser.SetDelimiters(new string[] { ";" });
parser.HasFieldsEnclosedInQuotes = true;
// Skip over header line.
//parser.ReadLine();
while (!parser.EndOfData)
{
var values = new List<string>();
var readFields = parser.ReadFields();
if (readFields != null)
values.AddRange(readFields);
result.Add(values);
}
}
return result;
}
I have written TinyCsvParser for .NET, which is one of the fastest .NET parsers around and highly configurable to parse almost any CSV format.
It is released under MIT License:
https://github.com/bytefish/TinyCsvParser
You can use NuGet to install it. Run the following command in the Package Manager Console.
PM> Install-Package TinyCsvParser
Usage
Imagine we have list of Persons in a CSV file persons.csv with their first name, last name and birthdate.
FirstName;LastName;BirthDate
Philipp;Wagner;1986/05/12
Max;Musterman;2014/01/02
The corresponding domain model in our system might look like this.
private class Person
{
public string FirstName { get; set; }
public string LastName { get; set; }
public DateTime BirthDate { get; set; }
}
When using TinyCsvParser you have to define the mapping between the columns in the CSV data and the property in you domain model.
private class CsvPersonMapping : CsvMapping<Person>
{
public CsvPersonMapping()
: base()
{
MapProperty(0, x => x.FirstName);
MapProperty(1, x => x.LastName);
MapProperty(2, x => x.BirthDate);
}
}
And then we can use the mapping to parse the CSV data with a CsvParser.
namespace TinyCsvParser.Test
{
[TestFixture]
public class TinyCsvParserTest
{
[Test]
public void TinyCsvTest()
{
CsvParserOptions csvParserOptions = new CsvParserOptions(true, new[] { ';' });
CsvPersonMapping csvMapper = new CsvPersonMapping();
CsvParser<Person> csvParser = new CsvParser<Person>(csvParserOptions, csvMapper);
var result = csvParser
.ReadFromFile(#"persons.csv", Encoding.ASCII)
.ToList();
Assert.AreEqual(2, result.Count);
Assert.IsTrue(result.All(x => x.IsValid));
Assert.AreEqual("Philipp", result[0].Result.FirstName);
Assert.AreEqual("Wagner", result[0].Result.LastName);
Assert.AreEqual(1986, result[0].Result.BirthDate.Year);
Assert.AreEqual(5, result[0].Result.BirthDate.Month);
Assert.AreEqual(12, result[0].Result.BirthDate.Day);
Assert.AreEqual("Max", result[1].Result.FirstName);
Assert.AreEqual("Mustermann", result[1].Result.LastName);
Assert.AreEqual(2014, result[1].Result.BirthDate.Year);
Assert.AreEqual(1, result[1].Result.BirthDate.Month);
Assert.AreEqual(1, result[1].Result.BirthDate.Day);
}
}
}
User Guide
A full User Guide is available at:
http://bytefish.github.io/TinyCsvParser/
Here is a short and simple solution.
using (TextFieldParser parser = new TextFieldParser(outputLocation))
{
parser.TextFieldType = FieldType.Delimited;
parser.SetDelimiters(",");
string[] headers = parser.ReadLine().Split(',');
foreach (string header in headers)
{
dataTable.Columns.Add(header);
}
while (!parser.EndOfData)
{
string[] fields = parser.ReadFields();
dataTable.Rows.Add(fields);
}
}
Here is my KISS implementation...
using System;
using System.Collections.Generic;
using System.Text;
class CsvParser
{
public static List<string> Parse(string line)
{
const char escapeChar = '"';
const char splitChar = ',';
bool inEscape = false;
bool priorEscape = false;
List<string> result = new List<string>();
StringBuilder sb = new StringBuilder();
for (int i = 0; i < line.Length; i++)
{
char c = line[i];
switch (c)
{
case escapeChar:
if (!inEscape)
inEscape = true;
else
{
if (!priorEscape)
{
if (i + 1 < line.Length && line[i + 1] == escapeChar)
priorEscape = true;
else
inEscape = false;
}
else
{
sb.Append(c);
priorEscape = false;
}
}
break;
case splitChar:
if (inEscape) //if in escape
sb.Append(c);
else
{
result.Add(sb.ToString());
sb.Length = 0;
}
break;
default:
sb.Append(c);
break;
}
}
if (sb.Length > 0)
result.Add(sb.ToString());
return result;
}
}
Some time ago I had wrote simple class for CSV read/write based on Microsoft.VisualBasic library. Using this simple class you will be able to work with CSV like with 2 dimensions array. You can find my class by the following link: https://github.com/ukushu/DataExporter
Simple example of usage:
Csv csv = new Csv("\t");//delimiter symbol
csv.FileOpen("c:\\file1.csv");
var row1Cell6Value = csv.Rows[0][5];
csv.AddRow("asdf","asdffffff","5")
csv.FileSave("c:\\file2.csv");
For reading header only you need is to read csv.Rows[0] cells :)
This code reads csv to DataTable:
public static DataTable ReadCsv(string path)
{
DataTable result = new DataTable("SomeData");
using (TextFieldParser parser = new TextFieldParser(path))
{
parser.TextFieldType = FieldType.Delimited;
parser.SetDelimiters(",");
bool isFirstRow = true;
//IList<string> headers = new List<string>();
while (!parser.EndOfData)
{
string[] fields = parser.ReadFields();
if (isFirstRow)
{
foreach (string field in fields)
{
result.Columns.Add(new DataColumn(field, typeof(string)));
}
isFirstRow = false;
}
else
{
int i = 0;
DataRow row = result.NewRow();
foreach (string field in fields)
{
row[i++] = field;
}
result.Rows.Add(row);
}
}
}
return result;
}
Single source file solution for straightforward parsing needs, useful. Deals with all the nasty edge cases. Such as new line normalization and handling new lines in quoted string literals. Your welcome!
If you CSV file has a header you just read out the column names (and compute column indexes) from the first row. Simple as that.
Note that Dump is a LINQPad method, you might want to remove that if you are not using LINQPad.
void Main()
{
var file1 = "a,b,c\r\nx,y,z";
CSV.ParseText(file1).Dump();
var file2 = "a,\"b\",c\r\nx,\"y,z\"";
CSV.ParseText(file2).Dump();
var file3 = "a,\"b\",c\r\nx,\"y\r\nz\"";
CSV.ParseText(file3).Dump();
var file4 = "\"\"\"\"";
CSV.ParseText(file4).Dump();
}
static class CSV
{
public struct Record
{
public readonly string[] Row;
public string this[int index] => Row[index];
public Record(string[] row)
{
Row = row;
}
}
public static List<Record> ParseText(string text)
{
return Parse(new StringReader(text));
}
public static List<Record> ParseFile(string fn)
{
using (var reader = File.OpenText(fn))
{
return Parse(reader);
}
}
public static List<Record> Parse(TextReader reader)
{
var data = new List<Record>();
var col = new StringBuilder();
var row = new List<string>();
for (; ; )
{
var ln = reader.ReadLine();
if (ln == null) break;
if (Tokenize(ln, col, row))
{
data.Add(new Record(row.ToArray()));
row.Clear();
}
}
return data;
}
public static bool Tokenize(string s, StringBuilder col, List<string> row)
{
int i = 0;
if (col.Length > 0)
{
col.AppendLine(); // continuation
if (!TokenizeQuote(s, ref i, col, row))
{
return false;
}
}
while (i < s.Length)
{
var ch = s[i];
if (ch == ',')
{
row.Add(col.ToString().Trim());
col.Length = 0;
i++;
}
else if (ch == '"')
{
i++;
if (!TokenizeQuote(s, ref i, col, row))
{
return false;
}
}
else
{
col.Append(ch);
i++;
}
}
if (col.Length > 0)
{
row.Add(col.ToString().Trim());
col.Length = 0;
}
return true;
}
public static bool TokenizeQuote(string s, ref int i, StringBuilder col, List<string> row)
{
while (i < s.Length)
{
var ch = s[i];
if (ch == '"')
{
// escape sequence
if (i + 1 < s.Length && s[i + 1] == '"')
{
col.Append('"');
i++;
i++;
continue;
}
i++;
return true;
}
else
{
col.Append(ch);
i++;
}
}
return false;
}
}
Another one to this list, Cinchoo ETL - an open source library to read and write multiple file formats (CSV, flat file, Xml, JSON etc)
Sample below shows how to read CSV file quickly (No POCO object required)
string csv = #"Id, Name
1, Carl
2, Tom
3, Mark";
using (var p = ChoCSVReader.LoadText(csv)
.WithFirstLineHeader()
)
{
foreach (var rec in p)
{
Console.WriteLine($"Id: {rec.Id}");
Console.WriteLine($"Name: {rec.Name}");
}
}
Sample below shows how to read CSV file using POCO object
public partial class EmployeeRec
{
public int Id { get; set; }
public string Name { get; set; }
}
static void CSVTest()
{
string csv = #"Id, Name
1, Carl
2, Tom
3, Mark";
using (var p = ChoCSVReader<EmployeeRec>.LoadText(csv)
.WithFirstLineHeader()
)
{
foreach (var rec in p)
{
Console.WriteLine($"Id: {rec.Id}");
Console.WriteLine($"Name: {rec.Name}");
}
}
}
Please check out articles at CodeProject on how to use it.
This parser supports nested commas and quotes in a column:
static class CSVParser
{
public static string[] ParseLine(string line)
{
List<string> cols = new List<string>();
string value = null;
for(int i = 0; i < line.Length; i++)
{
switch(line[i])
{
case ',':
cols.Add(value);
value = null;
if(i == line.Length - 1)
{// It ends with comma
cols.Add(null);
}
break;
case '"':
cols.Add(ParseEnclosedColumn(line, ref i));
i++;
break;
default:
value += line[i];
if (i == line.Length - 1)
{// Last character
cols.Add(value);
}
break;
}
}
return cols.ToArray();
}//ParseLine
static string ParseEnclosedColumn(string line, ref int index)
{// Example: "b"",bb"
string value = null;
int numberQuotes = 1;
int index2 = index;
for (int i = index + 1; i < line.Length; i++)
{
index2 = i;
switch (line[i])
{
case '"':
numberQuotes++;
if (numberQuotes % 2 == 0)
{
if (i < line.Length - 1 && line[i + 1] == ',')
{
index = i;
return value;
}
}
else if (i > index + 1 && line[i - 1] == '"')
{
value += '"';
}
break;
default:
value += line[i];
break;
}
}
index = index2;
return value;
}//ParseEnclosedColumn
}//class CSVParser
Based on unlimit's post on How to properly split a CSV using C# split() function? :
string[] tokens = System.Text.RegularExpressions.Regex.Split(paramString, ",");
NOTE: this doesn't handle escaped / nested commas, etc., and therefore is only suitable for certain simple CSV lists.
If anyone wants a snippet they can plop into their code without having to bind a library or download a package. Here is a version I wrote:
public static string FormatCSV(List<string> parts)
{
string result = "";
foreach (string s in parts)
{
if (result.Length > 0)
{
result += ",";
if (s.Length == 0)
continue;
}
if (s.Length > 0)
{
result += "\"" + s.Replace("\"", "\"\"") + "\"";
}
else
{
// cannot output double quotes since its considered an escape for a quote
result += ",";
}
}
return result;
}
enum CSVMode
{
CLOSED = 0,
OPENED_RAW = 1,
OPENED_QUOTE = 2
}
public static List<string> ParseCSV(string input)
{
List<string> results;
CSVMode mode;
char[] letters;
string content;
mode = CSVMode.CLOSED;
content = "";
results = new List<string>();
letters = input.ToCharArray();
for (int i = 0; i < letters.Length; i++)
{
char letter = letters[i];
char nextLetter = '\0';
if (i < letters.Length - 1)
nextLetter = letters[i + 1];
// If its a quote character
if (letter == '"')
{
// If that next letter is a quote
if (nextLetter == '"' && mode == CSVMode.OPENED_QUOTE)
{
// Then this quote is escaped and should be added to the content
content += letter;
// Skip the escape character
i++;
continue;
}
else
{
// otherwise its not an escaped quote and is an opening or closing one
// Character is skipped
// If it was open, then close it
if (mode == CSVMode.OPENED_QUOTE)
{
results.Add(content);
// reset the content
content = "";
mode = CSVMode.CLOSED;
// If there is a next letter available
if (nextLetter != '\0')
{
// If it is a comma
if (nextLetter == ',')
{
i++;
continue;
}
else
{
throw new Exception("Expected comma. Found: " + nextLetter);
}
}
}
else if (mode == CSVMode.OPENED_RAW)
{
// If it was opened raw, then just add the quote
content += letter;
}
else if (mode == CSVMode.CLOSED)
{
// Otherwise open it as a quote
mode = CSVMode.OPENED_QUOTE;
}
}
}
// If its a comma seperator
else if (letter == ',')
{
// If in quote mode
if (mode == CSVMode.OPENED_QUOTE)
{
// Just read it
content += letter;
}
// If raw, then close the content
else if (mode == CSVMode.OPENED_RAW)
{
results.Add(content);
content = "";
mode = CSVMode.CLOSED;
}
// If it was closed, then open it raw
else if (mode == CSVMode.CLOSED)
{
mode = CSVMode.OPENED_RAW;
results.Add(content);
content = "";
}
}
else
{
// If opened quote, just read it
if (mode == CSVMode.OPENED_QUOTE)
{
content += letter;
}
// If opened raw, then read it
else if (mode == CSVMode.OPENED_RAW)
{
content += letter;
}
// It closed, then open raw
else if (mode == CSVMode.CLOSED)
{
mode = CSVMode.OPENED_RAW;
content += letter;
}
}
}
// If it was still reading when the buffer finished
if (mode != CSVMode.CLOSED)
{
results.Add(content);
}
return results;
}
For smaller input CSV data LINQ is fully enough.
For example for the following CSV file content:
schema_name,description,utype
"IX_HE","High-Energy data","x"
"III_spectro","Spectrosopic data","d"
"VI_misc","Miscellaneous","f"
"vcds1","Catalogs only available in CDS","d"
"J_other","Publications from other journals","b"
when we read the whole content into single string called data, then
using System;
using System.IO;
using System.Linq;
var data = File.ReadAllText(Path2CSV);
// helper split characters
var newline = Environment.NewLine.ToCharArray();
var comma = ",".ToCharArray();
var quote = "\"".ToCharArray();
// split input string data to lines
var lines = data.Split(newline);
// first line is header, take the header fields
foreach (var col in lines.First().Split(comma)) {
// do something with "col"
}
// we skip the first line, all the rest are real data lines/fields
foreach (var line in lines.Skip(1)) {
// first we split the data line by comma character
// next we remove double qoutes from each splitted element using Trim()
// finally we make an array
var fields = line.Split(comma)
.Select(_ => { _ = _.Trim(quote); return _; })
.ToArray();
// do something with the "fields" array
}
I have looked all over for the answer to this, but I can't find it anywhere. I need to be able to clear a line from a txt file by the last integer in the line (the ID number), but I have no idea how to do that. Please help? Basically I was thinking that I need to find the last integer, and if it does not equal to the input, then it would move to the next line until it finds the right integer. Then that line is cleared. Here is some of my code that obviously doesn't work:
public static void TicID(CommandArgs args)
{
if (args.Parameters.Count == 1)
{
if (i == 1)
{
try
{
string idToDelete = args.Parameters[0];
StreamReader idreader = new StreamReader("Tickets.txt");
StreamWriter iddeleter = new StreamWriter("Tickets.txt");
string id = Convert.ToString(idreader.Read());
string line = null;
while (idreader.Peek() >= 0)
{
if (String.Compare(id, idToDelete) == 0)
{
iddeleter.WriteLine(line);
}
else
{
idreader.ReadLine();
}
}
}
The most straightforward way to delete lines is to write the lines that should not be deleted:
var idToDelete = "1";
var path = #"C:\Temp\Test.txt";
var lines = File.ReadAllLines(path);
using (var writer = new StreamWriter(path, false)) {
for (var i = 0; i < lines.Length; i++) {
var line = lines[i];
//assuming it's a CSV file
var cols = line.Split(',');
var id = cols[cols.Length - 1];
if (id != idToDelete) {
writer.WriteLine(line);
}
}
}
This is the LINQ-way:
var lines = from line in File.ReadAllLines(path)
let cols = line.Split(',')
let id = cols[cols.Length - 1]
where id != idToDelete
select line;
File.WriteAllLines(path, lines);
Create a StreamReader object and read line by line into a string array or something like that using StreamReader's instance method ReadLine() and now find your line of choice in your text array and delete it.
Important note:
do { /*see description above*/ } while (streamReader.Peak() != -1);