Reading CSV files using C#

Question

I'm writing a simple import application and need to read a CSV file, show result in a DataGrid and show corrupted lines of the CSV file in another grid. For example, show the lines that are shorter than 5 values in another grid. I'm trying to do that like this:

StreamReader sr = new StreamReader(FilePath);
importingData = new Account();
string line;
string[] row = new string [5];
while ((line = sr.ReadLine()) != null)
{
    row = line.Split(',');

    importingData.Add(new Transaction
    {
        Date = DateTime.Parse(row[0]),
        Reference = row[1],
        Description = row[2],
        Amount = decimal.Parse(row[3]),
        Category = (Category)Enum.Parse(typeof(Category), row[4])
    });
}

but it's very difficult to operate on arrays in this case. Is there any better way to split the values?

Answer 1

Sometimes using libraries are cool when you do not want to reinvent the wheel, but in this case one can do the same job with fewer lines of code and easier to read compared to using libraries. Here is a different approach which I find very easy to use.

1. In this example, I use StreamReader to read the file
2. Regex to detect the delimiter from each line(s).
3. An array to collect the columns from index 0 to n

---

using (StreamReader reader = new StreamReader(fileName))
    {
        string line; 

        while ((line = reader.ReadLine()) != null)
        {
            //Define pattern
            Regex CSVParser = new Regex(",(?=(?:[^\"]*\"[^\"]*\")*(?![^\"]*\"))");

            //Separating columns to array
            string[] X = CSVParser.Split(line);

            /* Do something with X */
        }
    }

Answer 2

CSV can get complicated real fast.

Use something robust and well-tested:
FileHelpers: www.filehelpers.net

The FileHelpers are a free and easy to use .NET library to import/export data from fixed length or delimited records in files, strings or streams.

Answer 3

I use this here:

http://www.codeproject.com/KB/database/GenericParser.aspx

Last time I was looking for something like this I found it as an answer to this question.

Answer 4

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

Answer 5

First of all need to understand what is CSV and how to write it.

1. Every next string ( /r/n ) is next "table" row.
2. "Table" cells is separated by some delimiter symbol. Most often used symbols is \t or ,
3. Every cell possibly can contain this delimiter symbol (cell must to start with quotes symbol and ends with this symbol in this case)
4. Every cell possibly can contains /r/n sybols (cell must to start with quotes symbol and ends with this symbol in this case)

The easiest way for C#/Visual Basic to work with CSV files is to use standard Microsoft.VisualBasic library. You just need to add needed reference, and the following string to your class:

using Microsoft.VisualBasic.FileIO;

Yes, you can use it in C#, don't worry. This library can read relatively big files and supports all of needed rules, so you will be able to work with all of CSV files.

Some time ago I had wrote simple class for CSV read/write based on this 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 using:

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");

Answer 6

I recommend CsvHelper from Nuget.

(Adding a reference to Microsoft.VisualBasic just doesn't feel right, it's not only ugly, it's probably not even cross-platform.)