Reading only one specific element from a CSV in C#

Question

I am fairly new to C# and I've been wrecking my head with a problem. I need to read one particular line/position from a CSV file (2nd line, 4th column), which ALWAYS hold the data I expect.

(If you're curious: this CSV file is a report and the first 3 lines are a header. The field in question holds a date)

Here is what I (sort of) started with after doing some research (and with my n00b C# skills):

        dt = new DataTable();
        string[] csvRows = System.IO.File.ReadAllLines(origFilePath);
        dt.Columns.Add(csvRows[0]);

        for (int x = 1; x < 2; x++)
        {
            dt.Rows.Add(csvRows[x]);
        }
        dt.Rows[0][0].ToString(); // must modify [0][0]

Thing is, the file can be quite big, so I don't think I need to read the entire file and setting it into a table object for then retrieving that value.

I'm sure there must be a better way?!

Can someone please advise? Thank you in advance for your help.

Regards, P.

Can you add a simple version of your csv file and show what you want to read? Probably you can directly read `mth` line and get `nth` column with a `String.Split(',')`. — Arghya C, Oct 09 '15 at 17:02
Possible duplicate of [Reading large text files with streams in C#](http://stackoverflow.com/questions/2161895/reading-large-text-files-with-streams-in-c-sharp) — saarrrr, Oct 09 '15 at 17:13

Anderson Pimentel · Accepted Answer · 2015-10-09T17:20:28.020

2

One-liner:

var myValue = System.IO.File.ReadLines(origFilePath).Skip(1).First().Split(',')[3];

I'm sure it's not the optimal way (I not even tested), but should do the trick.

Don't forget to import the Linq namespace (using System.Linq;).

edited Oct 09 '15 at 17:20

answered Oct 09 '15 at 17:02

Anderson Pimentel

5,086
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3

`File.ReadAllLines("file").Skip(1).First().Split(',')[3]` – Arghya C Oct 09 '15 at 17:05
1

Fixed. Thanks @ArghyaC ! – Anderson Pimentel Oct 09 '15 at 17:08
1

Wait, but ReadAllLines still reads the entire file. You should use ReadLines which does it in a lazy way.. – Maor Veitsman Oct 09 '15 at 17:15
Changed from `ReadAllLines` to `ReadLines`. Thanks @MaorVeitsman ! – Anderson Pimentel Oct 09 '15 at 17:21
Folks thank you for your help. Just did a simple console app to try this and it works beautifully -- indeed with a single line! – pmdci Oct 09 '15 at 17:24
2

In some cases, CSV value can be complicated and be in double quotes having comma inside ( value1, value2, "value 3, with comma", value4 ). This simple solution will fail in this case. – dlxeon Oct 09 '15 at 17:28
You are right but this particular case this is never going to happen because this particular 'cell' ALWAYS has the values in the way we expect. They are system generated. – pmdci Oct 09 '15 at 17:31

score 1 · Answer 2 · edited May 23 '17 at 11:52

You're looking for a lazy method to get what you need. Lazy means avoiding reading the entire file to get the right line.

using (FileStream fs = File.Open(path, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
using (BufferedStream bs = new BufferedStream(fs))
using (StreamReader sr = new StreamReader(bs))
{
    var i = 0;
    string line;
    while ((line = sr.ReadLine()) != null)
    {
        if (i == 4) //4th position = 5th line (3 header lines plus 2 data lines)
        {
            return line.split(',')[3];
        }
        i++;
    }
}

Code is partially ripped from here: Reading large text files with streams in C#

Alternatively, you can do:

var i = 0;
foreach (string line in File.ReadLines(filepath))
{
    if (i == 4)
    {
        return line.split(',')[3];
    }
    i++;
}

@pmdci Easy does it, I meant the code I provided which you would have seen had you followed my link instead of being defensive from the start, its from the top answer of the link I provided with your logic added. Jesus, you're welcome. — saarrrr, Oct 09 '15 at 17:07

score 0 · Answer 3 · answered Oct 09 '15 at 17:20

You can use oledb to read csv without opening. You can modify SQL statement to retrieve only column you need.

public class CSVReader
    {

        public DataSet ReadCSVFile(string fullPath, bool headerRow)
        {

            string path = fullPath.Substring(0, fullPath.LastIndexOf("\\") + 1);
            string filename = fullPath.Substring(fullPath.LastIndexOf("\\") + 1);
            DataSet ds = new DataSet();

            try
            {
                if (File.Exists(fullPath))
                {
                    string ConStr = string.Format("Provider=Microsoft.Jet.OLEDB.4.0;Data Source={0}" + ";Extended Properties=\"Text;HDR={1};FMT=Delimited\\\"", path, headerRow ? "Yes" : "No");
                    string SQL = string.Format("SELECT * FROM {0}", filename);
                    OleDbDataAdapter adapter = new OleDbDataAdapter(SQL, ConStr);
                    adapter.Fill(ds, "TextFile");
                    ds.Tables[0].TableName = "Table1";
                }
                foreach (DataColumn col in ds.Tables["Table1"].Columns)
                {
                    col.ColumnName = col.ColumnName.Replace(" ", "_");
                }
            }

            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
            return ds;
        }
    }

score 0 · Answer 4 · answered Dec 11 '18 at 06:08

Read line from CSV file, go directly to 15th position and get the value. Refer below c# code

namespace DBCreateTags
{
    class Program
    {
        static void Main(string[] args)
        {
            using (var reader = new StreamReader(@"T:\test.csv"))
            {
                while (!reader.EndOfStream)
                {
                    var line = reader.ReadLine();
                    var values = line.Split(',')[15];

                }
            }
        }

    }
}

Reading only one specific element from a CSV in C#

4 Answers4