c# - How to control formatting of floats with CsvHelper

Question

To control the format when writing datetimes one would do this

var options = new CsvHelper.TypeConversion.TypeConverterOptions { 
  Formats = new[] { 
    "yyyy-MM-dd HH:mm" 
  } 
};

I wish to similarly specify a picture string controlling the formatting of floats. I tried this.

var options = new CsvHelper.TypeConversion.TypeConverterOptions {
  Formats = new[] {
    "yyyy-MM-dd HH:mm", 
    "###.#" 
  } 
};

but it doesn't work.

How do you associate a format string with float or double?

I need to force the format to the picture string shown in my second sample ("###.#") because the FORTRAN program consuming the generated CSV is very fussy and will not accept "245" where it expects "245.0".

Source for the consuming program is not available. Suggesting that I fix that is not helpful.

question from:https://stackoverflow.com/questions/65623160/how-to-control-formatting-of-floats-with-csvhelper

Answer 1

To force adding 0 need to use zero placeholder:

public class Foo
{
    public int Id { get; set; }
    public string Name { get; set; }
    public DateTime Time { get; set; }
    public float Value1 { get; set; }
    public double Value2 { get; set; }
}

var records = new List<Foo>
{
    new Foo { Id = 1, Name = "one", Time = DateTime.Now, Value1 = 1.123f, Value2 = 12345.789 },
    new Foo { Id = 2, Name = "two", Time = DateTime.Now, Value1 = 123f, Value2 = 44 },
};

var dt_options = new CsvHelper.TypeConversion.TypeConverterOptions { 
    Formats = new[] {  "yyyy-MM-dd HH:mm" }  };
var float_options = new CsvHelper.TypeConversion.TypeConverterOptions { 
    Formats = new[] { "###.0" } };

using (var writer = new StreamWriter("file.csv"))
using (var csv = new CsvWriter(writer, CultureInfo.InvariantCulture))
{
    csv.Configuration.TypeConverterOptionsCache.AddOptions<DateTime>(dt_options);
    csv.Configuration.TypeConverterOptionsCache.AddOptions<float>(float_options);
    csv.Configuration.TypeConverterOptionsCache.AddOptions<double>(float_options);

    csv.WriteRecords(records);
}

Id,Name,Time,Value1,Value2
1,one,2021-01-07 20:54,1.1,12345.8
2,two,2021-01-07 20:54,123.0,44.0

Configure CsvWriter if required to wrap all values to quotes:

..
using (var csv = new CsvWriter(writer, 
    new CsvConfiguration(CultureInfo.InvariantCulture) { 
        ShouldQuote = (_, _) => true  }))
..

/*
"Id","Name","Time","Value1","Value2"
"1","one","2021-01-07 21:11","1.1","12345.8"
"2","two","2021-01-07 21:11","123.0","44.0"
*/