{"id":1272,"date":"2023-03-30T10:00:21","date_gmt":"2023-03-30T03:00:21","guid":{"rendered":"https:\/\/csharptutorial.net\/?page_id=1272"},"modified":"2023-03-30T10:08:38","modified_gmt":"2023-03-30T03:08:38","slug":"csharp-read-csv-file","status":"publish","type":"page","link":"https:\/\/www.csharptutorial.net\/csharp-file\/csharp-read-csv-file\/","title":{"rendered":"C# Read CSV File"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn how to use read CSV files in C# using the CsvHelper library.<\/p>\n\n\n\n

Introduction to the CSVhelper library<\/h2>\n\n\n\n

CsvHelper is a popular open-source library for reading and writing CSV (Comma Separated Value) files in C#. <\/p>\n\n\n\n

CSVHelper is fast, flexible, and easy to use. It provides you with features to customize the CSV parsing and writing process. For example, it can map CSV columns to object properties, specify custom delimiters and quotes, and handle type conversions and errors.<\/p>\n\n\n\n

The CsvHelper library is available as a NuGet package. Therefore, you need to install it via the command line or using Visual Studio’s NuGet Package Manager.<\/p>\n\n\n\n

Installing CsvHelper<\/h2>\n\n\n\n

The following shows you how to install the CsvHelper library using the package manager console, .Net CLI console, and Visual Studio:<\/p>\n\n\n\n

Package Manager Console<\/h3>\n\n\n
Install-Package CsvHelper<\/code><\/span><\/pre>\n\n\n
.NET CLI Console<\/h3>\n\n\n
dotnet add package CsvHelper<\/code><\/span><\/pre>\n\n\n
Visual Studio<\/h3>\n\n\n\n
If you use Visual Studio, you can follow these steps:<\/p>\n\n\n\n
First, right-click the Dependencies<\/code> and select the Manager NuGet Packages...<\/code> menu item:<\/p>\n\n\n\n
\"\"<\/figure>\n\n\n\n
Second, type the CsvHelper, choose the package as shown in the following picture, and click the Install<\/strong> button:<\/p>\n\n\n\n
\"\"<\/figure>\n\n\n\n
Preparing a sample CSV file for reading<\/h2>\n\n\n\n
Download the following data.csv file<\/a> and copy it to the project directory. To allow the program to read the CSV file, you need to change its setting so that Visual Studio will copy it to the output directory:<\/p>\n\n\n\n
\"\"<\/figure>\n\n\n\n
\"\"<\/figure>\n\n\n\n
Reading a CSV file into a collection of dynamic objects<\/h2>\n\n\n\n
The following program reads the data.csv file and converts CSV rows into dynamic objects:<\/p>\n\n\n
using CsvHelper;\r\nusing System.Globalization;\r\nusing static<\/span> System.Console;\r\n\r\n\r\nusing var<\/span> reader = new<\/span> StreamReader(\"data.csv\"<\/span>);\r\nusing var<\/span> csv = new<\/span> CsvReader(reader, CultureInfo.InvariantCulture);\r\n\r\n\/\/ read CSV file<\/span>\r\nvar<\/span> records = csv.GetRecords<dynamic>();\r\n\r\n\r\n\/\/ output<\/span>\r\nforeach<\/span> (var<\/span> r in records)\n{\n    WriteLine($\"{r.FirstName,-15}{r.LastName,-10}{r.JoinedDate,15}{r.Salary,15}{r.Active,5}\"<\/span>);\n}<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
John           Smith            2\/1\/2023     245,941.00  Yes\r\nSarah          Johnson          3\/1\/2023     208,902.00  Yes\r\nMichael        Brown            3\/1\/2023     215,970.00  Yes\r\nEmily          Davis            2\/1\/2023     239,648.00  Yes\r\nDavid          Wilson           3\/1\/2023     190,999.00  Yes\r\nJennifer       Martinez         2\/1\/2023     132,277.00  Yes\r\nRobert         Garcia           2\/1\/2023     157,395.00  Yes\r\nJessica        Lee              2\/1\/2023     210,666.00  Yes\r\nChristopher    Rodriguez        2\/1\/2023      83,272.00  Yes\r\nAmanda         Taylor           2\/1\/2023     143,537.00  Yes<\/code><\/span><\/pre>\n\n\n
How it works.<\/p>\n\n\n\n
First, create a StreamReader<\/code> object to read the contents of the CSV file data:<\/p>\n\n\n
using var<\/span> reader = new<\/span> StreamReader(\"data.csv\"<\/span>);<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
The using<\/code> statement ensures that the StreamReader<\/code> object is disposed properly.<\/p>\n\n\n\n
Second, create a new CsvHelper<\/code> object with the StreamReader<\/code> object and CultureInfo.InvariantCulture<\/code>. The CultureInfo.InvariantCulture<\/code> object specifies the culture settings for the CSV file.<\/p>\n\n\n
using var<\/span> csv = new<\/span> CsvReader(reader, CultureInfo.InvariantCulture);<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
Third, read the CSV file using the GetRecords<dynamic><\/code> method that returns an IEnumerable<dynamic><\/code>. Each object in the IEnumerable<dynamic><\/code> represents a row in the CSV file:<\/p>\n\n\n
var records = csv.GetRecords<dynamic<\/span>><\/span>();<\/code><\/span>Code language:<\/span> HTML, XML<\/span> (<\/span>xml<\/span>)<\/span><\/small><\/pre>\n\n\n
foreach<\/span> (var<\/span> r in records)\n{\n    WriteLine($\"{r.FirstName,-15}{r.LastName,-10}{r.JoinedDate,15}{r.Salary,15}{r.Active,5}\"<\/span>);\n}<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Reading a CSV file into a collection of specific objects<\/h2>\n\n\n\n
The following read the data.csv<\/code> file and convert each row to an Employee<\/code> object:<\/p>\n\n\n
using CsvHelper;\r\nusing System.Globalization;\r\nusing static<\/span> System.Console;\r\n\r\nclass<\/span> Employee<\/span>\n<\/span>{\r\n    public string? FirstName { get<\/span>; set<\/span>; }\r\n    public string? LastName { get<\/span>; set<\/span>; }\r\n    public DateOnly? JoinedDate { get<\/span>; set<\/span>; }\r\n    public decimal? Salary { get<\/span>; set<\/span>; }\r\n    public string? Active { get<\/span>; set<\/span>; }\r\n}\r\n\r\nclass Program\r\n{\r\n    static<\/span> void<\/span> Main(string[] args)\r\n    {\r\n        using var<\/span> reader = new<\/span> StreamReader(\"data.csv\"<\/span>);\r\n        using var<\/span> csv = new<\/span> CsvReader(reader, CultureInfo.InvariantCulture);\r\n\r\n        \/\/ Read CSV file<\/span>\r\n        var<\/span> employees = csv.GetRecords<Employee>();\r\n\r\n\r\n        \/\/ Output<\/span>\r\n        foreach (var<\/span> e in<\/span> employees)\r\n        {\r\n            WriteLine($\"{e.FirstName,-15}{e.LastName,-10}{e.JoinedDate,15}{e.Salary,15}{e.Active,5}\"<\/span>);\r\n        }\n    }\r\n}<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
How it works.<\/p>\n\n\n\n
First, define the Employee<\/code> class with the FirstName<\/code>, LastName<\/code>, JoinedDate<\/code>, Salary<\/code>, and Active<\/code> fields. Each field is corresponding to a column in the data.csv<\/code> file:<\/p>\n\n\n
class<\/span> Employee<\/span>\n<\/span>{\r\n    public string? FirstName { get<\/span>; set<\/span>; }\r\n    public string? LastName { get<\/span>; set<\/span>; }\r\n    public DateOnly? JoinedDate { get<\/span>; set<\/span>; }\r\n    public Decimal? Salary { get<\/span>; set<\/span>; }\r\n    public String? Active { get<\/span>; set<\/span>; }\r\n}<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
Second, read the data.csv<\/code> file and map each row to an Employee<\/code> object in the Main()<\/code> method of the Program<\/code> class:<\/p>\n\n\n
class<\/span> Program<\/span>\r\n<\/span>{\r\n    static<\/span> void<\/span> Main(string[] args)\r\n    {\r\n        using var<\/span> reader = new<\/span> StreamReader(\"data.csv\"<\/span>);\r\n        using var<\/span> csv = new<\/span> CsvReader(reader, CultureInfo.InvariantCulture);\r\n\r\n        \/\/ Read CSV file<\/span>\r\n        var<\/span> employees = csv.GetRecords<Employee>();\r\n\r\n\r\n        \/\/ Output<\/span>\r\n        foreach (var<\/span> e in<\/span> employees)\r\n        {\r\n            WriteLine($\"{e.FirstName,-15}{e.LastName,-10}{e.JoinedDate,15}{e.Salary,15}{e.Active,5}\"<\/span>);\r\n        }\n    }\r\n}\r\n<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
In this program, we pass the Employee<\/code> class to the GetRecords<Employee><\/code> instead of dynamic<\/code>. <\/p>\n\n\n\n
Reading a CSV file without a header<\/h2>\n\n\n\n
If you delete the header of the data.csv<\/code> file and execute the above program, you’ll get an exception. To avoid the error, you need to create a CsvConfiguration<\/code> object and pass it to the CsvHelper<\/code> class:<\/p>\n\n\n
using CsvHelper;\r\nusing CsvHelper.Configuration;\r\nusing System.Globalization;\r\nusing static<\/span> System.Console;\r\n\r\nclass<\/span> Employee<\/span>\n<\/span>{\r\n    public string? FirstName { get<\/span>; set<\/span>; }\r\n    public string? LastName { get<\/span>; set<\/span>; }\r\n    public DateOnly? JoinedDate { get<\/span>; set<\/span>; }\r\n    public Decimal? Salary { get<\/span>; set<\/span>; }\r\n    public String? Active { get<\/span>; set<\/span>; }\r\n}\r\n\r\nclass Program\r\n{\r\n    static<\/span> void<\/span> Main(string[] args)\r\n    {\r\n        using var<\/span> reader = new<\/span> StreamReader(\"data.csv\"<\/span>);\r\n\r\n        var<\/span> csvConfig = new<\/span> CsvConfiguration(CultureInfo.InvariantCulture)\r\n        {\r\n            HasHeaderRecord = false<\/span>\r\n        };\r\n\r\n        using var<\/span> csv = new<\/span> CsvReader(reader, csvConfig);\r\n\r\n        \/\/ Read CSV file<\/span>\r\n        var<\/span> employees = csv.GetRecords<Employee>();\r\n\r\r\n        \/\/ Output<\/span>\r\n        foreach (var<\/span> e in<\/span> employees)\r\n        {\r\n            WriteLine($\"{e.FirstName,-15}{e.LastName,-10}{e.JoinedDate,15}{e.Salary,15}{e.Active,5}\"<\/span>);\r\n        }\n    }\r\n}<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
Reading a CSV file with spaces in the header<\/h2>\n\n\n\n
If the header in the CSV file has spaces for example First Name<\/code> instead of FirstName<\/code>, you need to preprocess it before reading the file.<\/p>\n\n\n\n
To do that you can use PrepareHeaderForMatch<\/code> option of the CsvConfiguration<\/code> object. For example, you can remove the spaces like the following example:<\/p>\n\n\n
using CsvHelper;\r\nusing CsvHelper.Configuration;\r\nusing System.Globalization;\r\nusing static<\/span> System.Console;\r\n\r\nclass<\/span> Employee<\/span>\r\n<\/span>{\r\n    public string? FirstName { get<\/span>; set<\/span>; }\r\n    public string? LastName { get<\/span>; set<\/span>; }\r\n    public DateOnly? JoinedDate { get<\/span>; set<\/span>; }\r\n    public decimal? Salary { get<\/span>; set<\/span>; }\r\n    public string? Active { get<\/span>; set<\/span>; }\r\n}\r\n\r\nclass Program\r\n{\r\n    static<\/span> void<\/span> Main(string[] args)\r\n    {\r\n        using var<\/span> reader = new<\/span> StreamReader(\"data.csv\"<\/span>);\r\n\r\n        var<\/span> csvConfig = new<\/span> CsvConfiguration(CultureInfo.InvariantCulture)\r\n        {\r\n            PrepareHeaderForMatch = args<\/span> =><\/span> args.Header.Replace(\" \"<\/span>, string.Empty)\r\n        };\r\n\r\n        using var<\/span> csv = new<\/span> CsvReader(reader, csvConfig);\r\n\r\n        \/\/ Read CSV file<\/span>\r\n        var<\/span> employees = csv.GetRecords<Employee>();\r\n\r\n        \/\/ Output<\/span>\r\n        foreach (var<\/span> e in<\/span> employees)\r\n        {\r\n            WriteLine($\"{e.FirstName,-15}{e.LastName,-10}{e.JoinedDate,15}{e.Salary,15}{e.Active,5}\"<\/span>);\r\n        }\n    }\r\n}<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
In this program, we set the PrepareHeaderForMatch<\/code> option in the CsvConfiguration<\/code> object. We assign a lambda expression<\/a> to the PrepareHeaderForMatch<\/code> property. <\/p>\n\n\n\n
The lambda expression accepts a PrepareHeaderForMatchArgs<\/code> object and replaces the spaces in the CSV header.<\/p>\n\n\n
var<\/span> csvConfig = new<\/span> CsvConfiguration(CultureInfo.InvariantCulture)\r\n{\r\n    PrepareHeaderForMatch = args<\/span> =><\/span> args.Header.Replace(\" \"<\/span>, string.Empty)\r\n};<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
Summary<\/h2>\n\n\n\n
    \n
  • Use the CsvHelper package to read CSV files.<\/li>\n\n\n\n
  • Use the CsvConfiguration<\/code> object to customize the way the CsvHelper parses the CSV files.<\/li>\n<\/ul>\n
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    Was this tutorial helpful ?<\/div>\n\t\t
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Finally, write each row of the CSV file to the console using a foreach<\/a><\/code> loop. Note that we use the ,-15<\/code>, ,-10<\/code>, ,15<\/code>, ,15<\/code>, and ,5<\/code> format specifiers to format the output with appropriate padding and alignment:<\/p>\n\n\n