Migrating to v14.0.0

CsvHelper 14 lets you dispose a CsvWriter asynchronously, with await using, so that the last records are written with FlushAsync instead of the blocking Flush that Dispose calls. Most code needs no change. Code that implements ISerializer or IWriter needs a DisposeAsync method, and the package depends on System.Threading.Tasks.Extensions on .NET Framework 4.5 and 4.7 and .NET Standard 2.0.

Disposing a writer

Use await using where you write asynchronously:

public class Foo
{
    public int Id { get; set; }
}

using (var csv = new CsvWriter(writer, CultureInfo.InvariantCulture))
{
    await csv.WriteRecordsAsync(new List<Foo> { new Foo { Id = 1 } });
}

public class Foo
{
    public int Id { get; set; }
}

await using (var csv = new CsvWriter(writer, CultureInfo.InvariantCulture))
{
    await csv.WriteRecordsAsync(new List<Foo> { new Foo { Id = 1 } });
}

DisposeAsync flushes the writer with FlushAsync, then disposes the TextWriter (unless leaveOpen is true), with DisposeAsync on .NET Standard 2.1 and with FlushAsync and Dispose elsewhere. CsvWriter, CsvSerializer and WritingContext have it in the .NET Standard and .NET Framework 4.7 builds, not in the .NET Framework 4.5 build.

Implementing ISerializer or IWriter

ISerializer extends IAsyncDisposable in the .NET Standard and .NET Framework 4.7 builds, and IWriter in the .NET Standard 2.1 and .NET Framework 4.7 builds. An implementation needs a DisposeAsync method:

public class UpperCaseSerializer : ISerializer
{
    private readonly CsvSerializer inner;

    public UpperCaseSerializer(TextWriter textWriter)
    {
        inner = new CsvSerializer(textWriter, CultureInfo.InvariantCulture);
    }

    public WritingContext Context => inner.Context;

    public ISerializerConfiguration Configuration => inner.Configuration;

    public void Write(string[] fields) => inner.Write(fields.Select(f => f?.ToUpperInvariant()).ToArray());

    public Task WriteAsync(string[] fields) => inner.WriteAsync(fields.Select(f => f?.ToUpperInvariant()).ToArray());

    public void WriteLine() => inner.WriteLine();

    public Task WriteLineAsync() => inner.WriteLineAsync();

    public void Dispose() => inner.Dispose();
}

public class UpperCaseSerializer : ISerializer
{
    private readonly CsvSerializer inner;

    public UpperCaseSerializer(TextWriter textWriter)
    {
        inner = new CsvSerializer(textWriter, CultureInfo.InvariantCulture);
    }

    public WritingContext Context => inner.Context;

    public ISerializerConfiguration Configuration => inner.Configuration;

    public void Write(string[] fields) => inner.Write(fields.Select(f => f?.ToUpperInvariant()).ToArray());

    public Task WriteAsync(string[] fields) => inner.WriteAsync(fields.Select(f => f?.ToUpperInvariant()).ToArray());

    public void WriteLine() => inner.WriteLine();

    public Task WriteLineAsync() => inner.WriteLineAsync();

    public void Dispose() => inner.Dispose();

    public ValueTask DisposeAsync() => inner.DisposeAsync();
}