.NET-library to read and write CSV files. ("Comma-Separated Values", RFC 4180)
It contains
CsvReader: Reads CSV from files and streams. It enables you to perform Linq-Queries on CSV files.CsvWriter: Writes CSV to files and stream.CsvRecordWrapper: Maps the columns of the CSV file to the columns of yourDataTableor to the properties of anobjectand performs type conversions.CsvRecordWrappersupports aliases with wildcards for CSV column names and ships with a lot of supporting classes - most are data type converters for the most needed data types and an easy to implement interface to create converters of whatever data type you need.CsvAnalyzer: Analyzes CSV files to get the right parameters for proper reading automatically. This enables you, to read CSV files, that don't fit the standard.
FolkerKinzel.CsvTools serves as a dependency in FolkerKinzel.Contacts.IO - a small and easy to use framework for .NET, which allows to manage contact data of organizations and natural persons, including a data model and classes to persist it as vCard (*.vcf) or CSV.
IMPORTANT: On some systems the content of the CHM file is blocked. Before opening the file right click on the file icon, select Properties, and check the "Allow" checkbox (if it is present) in the lower right corner of the General tab in the Properties dialog.
(For the sake of better readability exception handling is ommitted in the following examples.)
using System.Text;
using FolkerKinzel.CsvTools;
namespace Examples;
public static class LinqOnCsvFile
{
public static void TestLinqOnCsvFile()
{
const string csvFileName = "LinqTest.csv";
File.WriteAllText(csvFileName, new StringBuilder()
.AppendLine("Name,City")
.AppendLine("Ingrid,Berlin")
.AppendLine("Joyce,New York")
.AppendLine("Horst,Hamburg")
.AppendLine("John,New York")
.ToString());
using var csvReader = new CsvReader(csvFileName);
Console.Write("How many people live in New York?: ");
Console.WriteLine(
csvReader.Read().Where(x => x["City"] == "New York").Count());
// Console Output: How many people live in New York?: 2
}
}using System.Data;
using System.Globalization;
using FolkerKinzel.CsvTools;
using FolkerKinzel.CsvTools.Helpers;
using FolkerKinzel.CsvTools.Helpers.Converters;
namespace Examples;
public static class CsvToDataTable
{
private const string PUPILS_NAME = "Name";
private const string SUBJECT = "Subject";
private const string LESSON_DAY = "Day";
private const string LESSON_BEGIN = "Begin";
private const string FILE_NAME = "DataTable.csv";
public static void TestCsvToDataTable()
{
using DataTable dataTable = InitDataTable();
CsvRecordWrapper wrapper = InitCsvRecordWrapper();
// Write the CSV file:
// (We can sort the columns of the CSV file differently than those
// of the DataTable - CsvRecordWrapper will reorder that.)
string[] columns =
new string[] { SUBJECT, LESSON_BEGIN, PUPILS_NAME, LESSON_DAY };
using (var writer = new CsvWriter(FILE_NAME, columns))
{
// (CsvWriter reuses the same record.)
wrapper.Record = writer.Record;
foreach (DataRow? obj in dataTable.Rows)
{
if (obj is DataRow dataRow)
{
// The properties of the CsvRecordWrapper match the columns
// of the DataTable in data type and order (but not the
// columns of the CSV file).
for (int i = 0; i < wrapper.Count; i++)
{
wrapper[i] = dataRow[i];
}
writer.WriteRecord();
}
}
}
dataTable.Clear();
// Refill the DataTable from the CSV-file:
using (var reader = new CsvReader(FILE_NAME))
{
foreach (CsvRecord record in reader.Read())
{
wrapper.Record = record;
DataRow dataRow = dataTable.NewRow();
dataTable.Rows.Add(dataRow);
// It doesn't matter that the columns in the CSV file have a
// different order than the columns of the DataTable:
// CsvRecordWrapper reorders that for us.
for (int i = 0; i < wrapper.Count; i++)
{
dataRow[i] = wrapper[i];
}
}
}
WriteConsole(dataTable);
// Console output:
// Csv file:
//
// Subject,Begin,Name,Day
// Piano,14:30:00,Susi Meyer, Wednesday
// Piano,15:15:00,Carl Czerny, Thursday
// ,, Frederic Chopin,
//
//
// Content of the refilled DataTable:
// Susi Meyer Piano 3 14:30:00
// Carl Czerny Piano 4 15:15:00
// Frederic Chopin <DBNull> < DBNull > < DBNull >
}
private static CsvRecordWrapper InitCsvRecordWrapper()
{
var wrapper = new CsvRecordWrapper();
// Store the stringConverter because you can reuse the same
// converter for more than one property in CsvRecordWrapper.
ICsvTypeConverter stringConverter =
CsvConverterFactory.CreateConverter(CsvTypeCode.String, maybeDBNull: true);
wrapper.AddProperty
(
new CsvProperty(PUPILS_NAME,
new string[] { PUPILS_NAME },
stringConverter)
);
wrapper.AddProperty
(
new CsvProperty(SUBJECT,
new string[] { SUBJECT },
stringConverter)
);
wrapper.AddProperty
(
new CsvProperty(LESSON_DAY,
new string[] { LESSON_DAY },
CsvConverterFactory
.CreateEnumConverter<DayOfWeek>("G", maybeDBNull: true))
);
wrapper.AddProperty
(
new CsvProperty(LESSON_BEGIN,
new string[] { LESSON_BEGIN },
CsvConverterFactory
.CreateConverter(CsvTypeCode.TimeSpan, maybeDBNull: true))
);
return wrapper;
}
private static DataTable InitDataTable()
{
var dataTable = new DataTable();
dataTable.Columns.Add(new DataColumn(PUPILS_NAME));
dataTable.Columns.Add(new DataColumn(SUBJECT));
dataTable.Columns.Add(new DataColumn(LESSON_DAY, typeof(DayOfWeek)));
dataTable.Columns.Add(new DataColumn(LESSON_BEGIN, typeof(TimeSpan)));
_ = dataTable.Rows.Add(
new object[] { "Susi Meyer", "Piano", DayOfWeek.Wednesday, new TimeSpan(14, 30, 0) });
_ = dataTable.Rows.Add(
new object[] { "Carl Czerny", "Piano", DayOfWeek.Thursday, new TimeSpan(15, 15, 0) });
_ = dataTable.Rows.Add(
new object[] { "Frederic Chopin" });
return dataTable;
}
private static void WriteConsole(DataTable dataTable)
{
Console.WriteLine("Csv file:");
Console.WriteLine();
Console.WriteLine(File.ReadAllText(FILE_NAME));
Console.WriteLine();
Console.WriteLine("Content of the refilled DataTable:");
foreach (DataRow? dataRow in dataTable.Rows)
{
if (dataRow is null)
{
continue;
}
const int padding = 15;
for (int i = 0; i < dataTable.Columns.Count; i++)
{
object o = dataRow[i];
Console.Write(o switch
{
null => "<null>".PadRight(padding),
DBNull dBNull => "<DBNull>".PadRight(padding),
string s when s.Length == 0 => "\"\"".PadRight(padding),
TimeSpan ts => ts.ToString("g", CultureInfo.InvariantCulture).PadRight(padding),
_ => o.ToString()?.PadRight(padding)
});
Console.Write(' ');
}
Console.WriteLine();
}
}
}using System.Text;
using FolkerKinzel.CsvTools;
using FolkerKinzel.CsvTools.Helpers;
using FolkerKinzel.CsvTools.Helpers.Converters;
namespace Examples;
public class Pupil
{
public string? Name { get; set; }
public string? Subject { get; set; }
public DayOfWeek? LessonDay { get; set; }
public TimeSpan? LessonBegin { get; set; }
public override string ToString()
{
const string NULL = "<null>";
return new StringBuilder()
.Append("Name: ").AppendLine(Name ?? NULL)
.Append("Subject: ").AppendLine(Subject ?? NULL)
.Append("LessonDay: ").AppendLine(LessonDay.HasValue
? $"{nameof(DayOfWeek)}.{LessonDay.Value}"
: NULL)
.Append("LessonBegin: ").AppendLine(LessonBegin.HasValue
? LessonBegin.Value.ToString()
: NULL)
.ToString();
}
}
public static class DeserializingClassesFromCsv
{
public static void TestDeserializingClassesFromCsv()
{
const string csvFileName = "Objects.csv";
// Create a nonstandard CSV-File
File.WriteAllText(csvFileName, new StringBuilder()
.AppendLine(
"Unterrichtstag;Unterrichtsbeginn;Vollständiger Name;Unterrichtsfach;")
.AppendLine(
"Wednesday;14:30;Susi Meyer;Piano")
.AppendLine(
"Thursday;15:15;Carl Czerny;Piano;")
.AppendLine(
";;Frederic Chopin")
.ToString());
// Initialize a CsvRecordWrapper which retrieves the data from
// the CSV-Columns and converts it to the right data type.
// Aliases with wildcards can be used to match the column-headers
// of the CSV file.
var wrapper = new CsvRecordWrapper();
// Reuse a converter for more than one property:
ICsvTypeConverter stringConverter =
CsvConverterFactory.CreateConverter(CsvTypeCode.String, nullable: true);
wrapper.AddProperty
(
new CsvProperty("Name",
new string[] { "*name" },
stringConverter)
);
wrapper.AddProperty
(
new CsvProperty("Subject",
new string[] { "*subject", "*fach" },
stringConverter)
);
wrapper.AddProperty
(
new CsvProperty("LessonDay",
new string[] { "*day", "*tag" },
CsvConverterFactory
.CreateEnumConverter<DayOfWeek>(nullable: true))
);
wrapper.AddProperty
(
new CsvProperty("LessonBegin",
new string[] { "*begin?" },
CsvConverterFactory
.CreateConverter(CsvTypeCode.TimeSpan, nullable: true))
);
// Analyze the CSV file to determine the right parameters
// for proper reading:
var analyzer = new CsvAnalyzer();
analyzer.Analyze(csvFileName);
// Read the CSV file:
using var reader =
new CsvReader(csvFileName,
analyzer.HasHeaderRow,
analyzer.Options,
analyzer.FieldSeparator);
var pupilsList = new List<Pupil>();
foreach (CsvRecord record in reader.Read())
{
wrapper.Record = record;
// Using a dynamic variable enables you to assign
// the properties without having to explicitely cast them
// to the target data type:
dynamic dynWrapper = wrapper;
pupilsList.Add(new Pupil
{
Name = dynWrapper.Name,
LessonBegin = dynWrapper.LessonBegin,
LessonDay = dynWrapper.LessonDay,
Subject = dynWrapper.Subject
});
}
// Write the results to Console:
foreach (Pupil pupil in pupilsList)
{
Console.WriteLine(pupil);
Console.WriteLine();
}
}
}
/*
Console output:
Name: Susi Meyer
Subject: Piano
LessonDay: DayOfWeek.Wednesday
LessonBegin: 14:30:00
Name: Carl Czerny
Subject: Piano
LessonDay: DayOfWeek.Thursday
LessonBegin: 15:15:00
Name: Frederic Chopin
Subject: <null>
LessonDay: <null>
LessonBegin: <null>
*/