public class MemoryPostedFile : HttpPostedFileBase
{
    private readonly byte[] fileBytes;

    public MemoryPostedFile(byte[] fileBytes, string fileName = null)
    {
        this.fileBytes = fileBytes;
        this.FileName = fileName;
        this.InputStream = new MemoryStream(fileBytes);
    }

    public override int ContentLength => fileBytes.Length;

    public override string FileName { get; }

    public override Stream InputStream { get; }
}