CsvHelper Failing to Handle DateTime on GitHub Build

Using net6.0.
Using CsvHelper 30.0.1

So when building locally the build succeeds without issue, however when committing to Github the Build fails with the following error:

CsvHelper.TypeConversion.TypeConverterException : The conversion cannot be performed.
    Text: '03/20/2023'
    MemberName: StartDate
    MemberType: System.Nullable`1[[System.DateTime, System.Private.CoreLib, Version=, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]]
    TypeConverter: 'CsvHelper.TypeConversion.NullableConverter'
IReader state:
   ColumnCount: 0
   CurrentIndex: 2
IParser state:
   ByteCount: 0
   CharCount: 56
   Row: 2
   RawRow: 2
   Count: 4
1,Test name,03/20/2023,0.12

Here is the code:

public class CsvProcessingServiceTests
    public void GetCsvStreamAsTransactionTypeTest()
        var testObject = new CsvProcessingServiceTestObject
            Id = 1,
            Name = "Test name",
            StartDate = DateTime.ParseExact("2023-03-20", "yyyy-MM-dd", 
            TotalSpend = (decimal?)0.12
        var testObjectInput = testObject.GetCSV();
        var testStream = new MemoryStream(Encoding.UTF8.GetBytes(testObjectInput));

        var result = _csvProcessingService.GetCsvStreamAsTransactionType<CsvProcessingServiceTestObject>(new StreamReader(testStream));

    private class CsvProcessingServiceTestObject
        public string GetCSV()
            var objectAsString = new StringBuilder();
            return objectAsString.ToString();
        public int? Id { get; set; }
        public string? Name { get; set; }
        public DateOnly? StartDate { get; set; }
        public decimal? TotalSpend { get; set; }

public class CsvProcessingService {
    private readonly CsvConfiguration _csvConfiguration;
    public CsvProcessingService()
        _csvConfiguration = new CsvConfiguration(CultureInfo.GetCultureInfo("en-GB"))
            TrimOptions = TrimOptions.Trim,
            HeaderValidated = null,
            MissingFieldFound = null

    public List<T> GetCsvStreamAsTransactionType<T>(StreamReader inputStreamReader)
        using var sr = new StreamReader(inputStreamReader);
        using var csv = new CsvReader(sr, _csvConfiguration);
        var csvRecords = csv.GetRecords<T>().ToList();
        return csvRecords;


Anyone have any ideas? I changed the (StartDate) DateTime to DateOnly but that also seemed to fail. It only seems to work when StartDate is set to a string.
Is there an issue with the GitHub Build? Why does it work when running locally in VS but not when commited to GitHub?

>Solution :

Try changing your GetCsv to provide culture info for StartDate?.Date.ToString:

objectAsString.Append($"{Id},{Name},{StartDate?.Date.ToString("d", CultureInfo.GetCultureInfo("en-GB"))},{TotalSpend}");

en-Gb should process dates as day–month–year while 03/20/2023 (value from error) obviously is not.

Or just use fixed custom formatting and do not rely on culture and standard formats.

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