Migrating to v26.0.0

CsvHelper 26 undoes the init properties of 25: they caused compiler problems for too many people. The args of the configuration functions have constructors with parameters again, and their members are read-only fields. It also adds ExceptionMessagesContainRawData, to keep CSV data out of exception messages, which adds a property to the configuration interfaces. Code that only receives args in a callback doesn't change; you are affected if you create args yourself or implement IParserConfiguration or IWriterConfiguration. The target frameworks don't change.

Delegate args

Create the args with their constructor instead of an object initializer.

PrepareHeaderForMatch prepareHeader = args => args.Header.Trim().ToLower();

var header = prepareHeader(new PrepareHeaderForMatchArgs
{
    Header = " Name ",
    FieldIndex = 0,
});

PrepareHeaderForMatch prepareHeader = args => args.Header.Trim().ToLower();

var header = prepareHeader(new PrepareHeaderForMatchArgs(" Name ", 0));

• From 24: the constructors are the ones 24 had, except BadDataFoundArgs, which takes the raw record as its second parameter.
• Fields, not properties: reading a member, such as args.Field, compiles as before, but an assembly built against 25 that reads the args has to be rebuilt against 26.
• CsvParser.ProcessedField, the struct that CsvParser subclasses get from the Process...Field methods, is created with new ProcessedField(start, length, buffer) too.

Raw data in exception messages

Exception messages show the raw record, and a TypeConverterException shows the text it couldn't convert. If your CSV files hold data that must not end up in logs, set ExceptionMessagesContainRawData to false: the messages say the data is hidden instead. It is true by default, so messages are as before unless you change it.

var config = new CsvConfiguration(CultureInfo.InvariantCulture)
{
    ExceptionMessagesContainRawData = false,
};
using var csv = new CsvReader(reader, config);

Custom configuration classes

IParserConfiguration and IWriterConfiguration each get the new property: bool ExceptionMessagesContainRawData { get; }. A class that implements either of them adds it.

public class ParserConfiguration : IParserConfiguration
{
    public bool CacheFields => false;
    public bool LeaveOpen => false;
    public string NewLine => "\r\n";
    public bool IsNewLineSet => false;
    public CsvMode Mode => CsvMode.RFC4180;
    public int BufferSize => 0x1000;
    public int ProcessFieldBufferSize => 1024;
    public bool CountBytes => false;
    public Encoding Encoding => Encoding.UTF8;
    public BadDataFound BadDataFound => ConfigurationFunctions.BadDataFound;
    public bool LineBreakInQuotedFieldIsBadData => false;
    public char Comment => '#';
    public bool AllowComments => false;
    public bool IgnoreBlankLines => true;
    public char Quote => '"';
    public string Delimiter => ",";
    public char Escape => '"';
    public TrimOptions TrimOptions => TrimOptions.None;
    public char[] WhiteSpaceChars => new[] { ' ', '\t' };
}

public class ParserConfiguration : IParserConfiguration
{
    public bool CacheFields => false;
    public bool LeaveOpen => false;
    public string NewLine => "\r\n";
    public bool IsNewLineSet => false;
    public CsvMode Mode => CsvMode.RFC4180;
    public int BufferSize => 0x1000;
    public int ProcessFieldBufferSize => 1024;
    public bool CountBytes => false;
    public Encoding Encoding => Encoding.UTF8;
    public BadDataFound BadDataFound => ConfigurationFunctions.BadDataFound;
    public bool LineBreakInQuotedFieldIsBadData => false;
    public char Comment => '#';
    public bool AllowComments => false;
    public bool IgnoreBlankLines => true;
    public char Quote => '"';
    public string Delimiter => ",";
    public char Escape => '"';
    public TrimOptions TrimOptions => TrimOptions.None;
    public char[] WhiteSpaceChars => new[] { ' ', '\t' };
    public bool ExceptionMessagesContainRawData => true; // New in 26.
}

A class that implements IReaderConfiguration adds it too, because IReaderConfiguration extends IParserConfiguration. A record that derives from CsvConfiguration already has it.

Behavior changes

• Header record in exception messages: the details of a CsvHelperException thrown while reading list the header record. 25 printed [""] instead, by mistake.