Reading CSV Files Using C#

Reading CSV files using C#

Don't reinvent the wheel. Take advantage of what's already in .NET BCL.

• add a reference to the Microsoft.VisualBasic (yes, it says VisualBasic but it works in C# just as well - remember that at the end it is all just IL)
• use the Microsoft.VisualBasic.FileIO.TextFieldParser class to parse CSV file

Here is the sample code:

using (TextFieldParser parser = new TextFieldParser(@"c:\temp\test.csv"))
{
    parser.TextFieldType = FieldType.Delimited;
    parser.SetDelimiters(",");
    while (!parser.EndOfData) 
    {
        //Processing row
        string[] fields = parser.ReadFields();
        foreach (string field in fields) 
        {
            //TODO: Process field
        }
    }
}

It works great for me in my C# projects.

Here are some more links/informations:

• MSDN: Read From Comma-Delimited Text Files in Visual Basic
• MSDN: TextFieldParser Class

Read a .csv file in c# efficiently?

Method 1

By using LINQ:

var Lines = File.ReadLines("FilePath").Select(a => a.Split(';'));
var CSV = from line in Lines 
          select (line.Split(',')).ToArray();

Method 2

As Jay Riggs stated here

Here's an excellent class that will copy CSV data into a datatable using the structure of the data to create the DataTable:

A portable and efficient generic parser for flat files

It's easy to configure and easy to use. I urge you to take a look.

Method 3

Rolling your own CSV reader is a waste of time unless the files that you're reading are guaranteed to be very simple. Use a pre-existing, tried-and-tested implementation instead.

Parsing CSV files in C#, with header

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!

Basic Read CSV File Questions

What I am not understanding since this CSV files 150+ fields, is how do grab the correct data

By index, because there is no header

In your BQFile, decorate the properties with an attribute of [Index(NNN)] where N is the column number (0-based). The IndexAttribute is found in CsvHelper.Configuration.Attributes namespace - I mention this because Entity Framework also has an Index attribute; be sure you use the correct one

pubic class BQFile{
  [Index(46)]
  public string SNumber { get; set;}

  ...
}

Then do:

        var config = new CsvConfiguration(CultureInfo.InvariantCulture)
        {
            HasHeaderRecord = false,
        };
        using (var reader = new StreamReader(iFile.FileName))
        using (var csv = new CsvReader(reader, config))
        {
            var records = csv.GetRecords<BQFile>();

            ...

records is an enumeration on top of the file stream (via CSVHelper, which reads records as it goes and creates instances of BQFile). You can only enumerate it once, and then after you're done enumerating it the filestream will be at the end - if you wanted to re-read the file you'd have to Seek the stream or renew the reader. Also, the file is only read (in chunks, progressively) as you enumerate. If you return records somewhere, so you drop out of the using and you thus dispose the reader, you'll get an error when you try to start reading from records (because it's disposed)

To work with records, you either foreach it, processing the objects you get as you go:

foreach(BQFile bqf in records){
  //do stuff with each BQFile here
}

Or if you want to load it all into memory, you can do something like ToList() it so you end up with a bunch of BQFile in a List, and then you can e.g. access them randomly, read them over and over etc..

var bqfs = records.ToList();

ps; I don't know, when you said "it's column 46" if that's counting from 1 or 0.. You might have to adjust your 46.

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