private FixedSizeTreePage GetPageForUpdate(LowLevelTransaction lltx, long key, byte depth)
{
var buffer = GetBufferForKey(lltx, key, depth);
if (buffer == null)
{
throw new NullReferenceException($"can't find a page for the key:{key.ToString()}");
}
var fixedPage = lltx.EnterWrite(buffer).AsFixed();
if (fixedPage == null)
{
throw new NullReferenceException(nameof(fixedPage));
}
return(fixedPage);
}