How can I build an in-memory tar file from SQL Server varbinary(max) columns using .NET 8's native Tar API?

Starting with .NET 8, you can use the native tar API provided in the System.Formats.Tar namespace, which includes classes like TarWriter and TarEntry. This lets you create tar files without needing third-party libraries such as SharpZipLib.

For example, your pseudocode can be adapted as follows:

CSHARPCopied
using System;
using System.Data.SqlClient;
using System.Formats.Tar;
using System.IO;
using System.Threading.Tasks;

public async Task CreateTarFromDatabaseFilesAsync()
{
    // Create a MemoryStream to store the .tar file in memory.
    using var tarStream = new MemoryStream();
    await using var tarWriter = new TarWriter(tarStream, leaveOpen: true);

    // Open a connection to SQL Server.
    await using var connection = new SqlConnection("YourConnectionString");
    await connection.OpenAsync();

    var command = new SqlCommand("SELECT FileName, FileData FROM FilesTable", connection);
    await using var reader = await command.ExecuteReaderAsync();

    while (await reader.ReadAsync())
    {
        var fileName = reader.GetString(0);
        // GetStream works if SQL Server's varbinary(max) returns a stream.
        var fileDataStream = reader.GetStream(1);

        // Create a TarEntry for the file.
        // You can set additional metadata on TarEntry if needed.
        TarEntry entry = TarEntry.CreateEntryFromFile(fileName);
        entry.DataStream = fileDataStream;

        // Write the entry to the tar file.
        tarWriter.WriteEntry(entry);
    }

    // Reset the stream's position if you plan to read from it.
    tarStream.Position = 0;

    // tarStream now contains the tar file data. Write it to the HTTP response or save it as needed.
    // For example, to write to an HTTP response stream:
    // await tarStream.CopyToAsync(responseStream);
}

Notes:

• The example shows one way of creating a TarEntry from a file name and stream. Depending on your scenario, you might need to set properties such as file size, modification time, or file permissions on the entry.
• The API in System.Formats.Tar is available in .NET 8 and later. Check the official documentation for any changes or additional members if you need further customization.
• The leaveOpen parameter in TarWriter's constructor is useful if you plan to use the underlying stream after writing.

Thus, with .NET 8’s built-in support, you can achieve your task without resorting to third-party libraries.