server/src/Core/Models/Data/CipherAttachment.cs

using System;
using System.Text.Json.Serialization;

namespace Bit.Core.Models.Data
{
    public class CipherAttachment
    {
        public Guid Id { get; set; }
        public Guid? UserId { get; set; }
        public Guid? OrganizationId { get; set; }
        public string AttachmentId { get; set; }
        public string AttachmentData { get; set; }

        public class MetaData
        {
            private long _size;

            // We serialize Size as a string since JSON (or Javascript) doesn't support full precision for long numbers
            [JsonNumberHandling(JsonNumberHandling.AllowReadingFromString | JsonNumberHandling.WriteAsString)]
            public long Size
            {
                get { return _size; }
                set { _size = value; }
            }

            public string FileName { get; set; }
            public string Key { get; set; }

            public string ContainerName { get; set; } = "attachments";
            public bool Validated { get; set; } = true;

            // This is stored alongside metadata as an identifier. It does not need repeating in serialization
            [JsonIgnore]
            public string AttachmentId { get; set; }
        }
    }
}