Custom conversions when writing CSV files using CsvHelper
You can do it with a custom type converters (https://github.com/JoshClose/CsvHelper/wiki/Custom-TypeConverter). Just override ConvertToString
method.
public class TestConverter : DefaultTypeConverter
{
public override string ConvertToString(TypeConverterOptions options, object value)
{
return base.ConvertToString(options, value);
}
}
and specify converter when mapping:
Map(m => m.PersonId).Index(0).TypeConverter<TestConverter>();
Mike Christensen
Founder and Chief Architect of KitchenPC.com, the world's most powerful recipe search engine. The technology behind KitchenPC is open-source, and available on GitHub.
Updated on July 22, 2022Comments
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Mike Christensen almost 2 years
I've been doing some CSV reading and writing lately, and ran across CsvHelper which is fantastic so far. I've ran into one small problem; I use a custom converter when reading the files, but when I write them back out, that format is lost. My CSV format looks like this:
67,1234-1,20150115,750,20150115,1340,549,549,406,0,FRG
The fields
20150115,750
map to a singleDateTime
field calledStart
(So, 01/15/2015 7:50 AM). My class map looks like this:public sealed class DutyMap : CsvClassMap<Duty> { static readonly CultureInfo enUS = new CultureInfo("en-US"); public DutyMap() { Map(m => m.PersonId).Index(0); Map(m => m.DutyName).Index(1); Map(m => m.Start).ConvertUsing(row => ParseDate(row.GetField<String>(2), row.GetField<String>(3))); Map(m => m.End).ConvertUsing(row => ParseDate(row.GetField<String>(4), row.GetField<String>(5))); Map(m => m.DutyTime1).Index(6); Map(m => m.DutyTime2).Index(7); Map(m => m.FlightTime).Index(8); Map(m => m.CreditHours).Index(9); Map(m => m.DutyType).Index(10); } private static DateTime ParseDate(string date, string time) { DateTime ret; if (time.Length < 4) time = new String('0', 4 - time.Length) + time; if (!DateTime.TryParseExact(date + time, "yyyyMMddHHmm", enUS, DateTimeStyles.None, out ret)) throw new FormatException(String.Format("Could not parse DateTime. Date: {0} Time: {1}", date, time)); return ret; } }
This works great, and I can now call parse an entire file like so:
var csv = new CsvReader(sr); csv.Configuration.HasHeaderRecord = false; csv.Configuration.RegisterClassMap<DutyMap>(); Data = csv.GetRecords<Duty>().ToList();
However, when I write the file:
csv.WriteRecords(Data);
The file is written out like so:
67,7454-1,1/15/2015 7:50:00 AM,1/15/2015 1:40:00 PM,549,549,406,0,FPG
Looking through the documentation, I don't see a way to specify a conversation function upon writing, only reading. The only solution I've found so far is to manually write each record by hand:
var csv = new CsvWriter(sw); foreach (var item in Data) { csv.WriteField(item.PersonId); csv.WriteField(item.DutyName); csv.WriteField(item.Start.ToString("yyyyMMdd")); csv.WriteField(item.Start.ToString("Hmm")); csv.WriteField(item.End.ToString("yyyyMMdd")); csv.WriteField(item.End.ToString("Hmm")); csv.WriteField(item.DutyTime1); csv.WriteField(item.DutyTime2); csv.WriteField(item.FlightTime); csv.WriteField(item.CreditHours); csv.WriteField(item.DutyType); csv.NextRecord(); }
Is there a better way to do this? Thanks!
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Mike Christensen over 8 yearsThanks! I started looking at that, but the documentation looked a bit sparse. I'll dig into it more!
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Mike Christensen over 8 yearsOh, also would this let me split one field (
Start
) into two different fields in the CSV file? Remember, I have to split up the date portion and time portion. -
Daniel Luberda over 8 yearsJust use Map statements multiple times with different columns names Map(m => m.PersonId).Index(0).Name("col1"); Map(m => m.PersonId).Index(0).Name("col2");
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Vasily Hall over 6 yearsI had to use this code: public override object ConvertFromString(string text, IReaderRow row, MemberMapData memberMapData)