Read CSV into Typed Objects

Choose the read path by what happens next. Load a CsvDocument when you will edit, sort, filter, or save the rows. Open a CsvDataReader when you read once, from start to end: it does not keep the file in memory, and it is a DbDataReader, so it plugs into anything that accepts one.

Map rows to objects

RowsAs<T> matches headers to writable properties or constructor parameters. Matching ignores case, spaces, and punctuation, so Order Date maps to OrderDate.

C#

using OfficeIMO.CSV;

List<Person> people = CsvDocument.Load("people.csv")
    .RowsAs<Person>()
    .ToList();

foreach (Person person in people) {
    Console.WriteLine($"{person.Name} ({person.Age}) lives in {person.City}");
}

public sealed class Person {
    public string Name { get; set; } = "";
    public int Age { get; set; }
    public string City { get; set; } = "";
}

PowerShell

Import-OfficeCsv -Path .\people.csv | Where-Object City -eq 'London'
Import-OfficeCsv -Path .\people.csv -As Hashtable | ForEach-Object { $_['Name'] }

Stream a large file

The forward-only reader never loads the whole file. RowsAs<T> works on it too, through OfficeIMO.Data.

C#

using OfficeIMO.CSV;
using OfficeIMO.Data;

using CsvDataReader reader = CsvDocument.OpenReader("events.csv");
int errors = 0;
foreach (LogEvent item in reader.RowsAs<LogEvent>()) {
    if (item.Level == "Error") errors++;
}
Console.WriteLine($"{errors} errors");

public sealed record LogEvent(DateTime Time, string Level, string Message);

On .NET 8 and later, CsvDocument.OpenReaderAsync and RowsAsAsync<T> read with asynchronous I/O and observe cancellation between rows.

Infer column types

With InferSchema, the reader samples the first rows and returns typed values (int, decimal, DateTime, bool) instead of strings.

C#

using OfficeIMO.CSV;

using CsvDataReader reader = CsvDocument.OpenReader("orders.csv",
    new CsvReaderOptions { InferSchema = true, SchemaSampleRows = 1000 });

int amount = reader.GetOrdinal("Amount");
decimal total = 0;
while (reader.Read()) {
    total += reader.GetDecimal(amount);
}
Console.WriteLine(total);

PowerShell

Import-OfficeCsv -Path .\orders.csv -InferSchema | Measure-Object Amount -Sum

CLI

Print the inferred schema of a file:

officeimo tabular schema orders.csv

Limits and reference

Limits: see the CSV package row. Input-size, field-length, and decompression limits are on CsvLoadOptions and CsvReaderOptions.

Reference: OfficeIMO.CSV API · Import-OfficeCsv