Implementation for in memory json provider for use with ConfigurationBuilder.

InMemoryJsonProvider.cs

        public class InMemoryJsonProvider : IFileProvider
        {
            private IFileInfo _file;

            public InMemoryJsonProvider(string json)
            {
                _file = new MemoryFileInfo(json);
            }

            public IDirectoryContents GetDirectoryContents(string subpath)
            {
                throw new NotImplementedException();
            }

            public IFileInfo GetFileInfo(string subpath)
            {
                return _file;
            }

            public IChangeToken Watch(string filter)
            {
                throw new NotImplementedException();
            }

            private class MemoryFileInfo : IFileInfo
            {
                readonly byte[] _content;

                public MemoryFileInfo(string json)
                {
                    Name = "config.json";
                    _content = Encoding.UTF8.GetBytes(json);
                    LastModified = DateTime.Now;
                }

                public bool Exists => true;

                long IFileInfo.Length => _content.LongLength;

                public string PhysicalPath => null;

                public string Name { get; }

                public DateTimeOffset LastModified { get; }

                public bool IsDirectory => false;

                public Stream CreateReadStream()
                {
                    return new MemoryStream(_content);
                }
            }
        }