<PackageReference Include="Newtonsoft.Json" Version="12.0.3" />

Newtonsoft.Json.Utilities.Base64Encoder

namespace Newtonsoft.Json.Utilities { internal class Base64Encoder { public Base64Encoder(TextWriter writer); public void Encode(byte[] buffer, int index, int count); public void Flush(); public async Task EncodeAsync(byte[] buffer, int index, int count, CancellationToken cancellationToken); public Task FlushAsync(CancellationToken cancellationToken); } }