public async Task GetItemsCursorPaging(PagingCursorArgs args)
{
var watch = System.Diagnostics.Stopwatch.StartNew();
var query = _demoDbContext.Items;
var time = args.PageCursor != null ? new DateTimeOffset(args.PageCursor.Value, TimeSpan.Zero) : new DateTimeOffset(DateTime.MinValue, TimeSpan.Zero);
_itemsCursorPagingLoading.OnNext(true);
// get page size + 1 item (for next cursor data)
var items = await query
.OrderBy(x => x.CreateDate)
.Where(x => x.CreateDate >= time)
.Take(args.PageSize + 1).ToListAsync();
// get previous cursor
var firstItem = items.FirstOrDefault()?.CreateDate;
var previous = await query
.OrderByDescending(x => x.CreateDate)
.Where(x => x.CreateDate < firstItem)
.Take(args.PageSize).LastOrDefaultAsync();
_itemsCursorPaging.OnNext(new PagingCursorData
{
Items = items.Take(args.PageSize).ToList(),
Total = await query.CountAsync(),
NextPage = items.LastOrDefault()?.CreateDate.Ticks,
PreviousPage = previous?.CreateDate.Ticks
});
watch.Stop();
_execTime.OnNext($"Execution Time: {watch.ElapsedMilliseconds} ms");
_itemsCursorPagingLoading.OnNext(false);
}
public async Task Delete(PagingCursorArgs args)
{
if (args.PageCursor == null)
{
return;
}
var query = _demoDbContext.Items;
var time = args.PageCursor != null ? new DateTimeOffset(args.PageCursor.Value, TimeSpan.Zero) : new DateTimeOffset(DateTime.MinValue, TimeSpan.Zero);
_itemsCursorPagingLoading.OnNext(true);
var previous = await query
.OrderByDescending(x => x.CreateDate)
.Where(x => x.CreateDate < time)
.Take(args.PageSize).ToListAsync();
if (previous.Count == 0)
{
return;
}
int index = new Random().Next(previous.Count);
var itemDelete = previous[index];
_demoDbContext.Items.Remove(itemDelete);
await _demoDbContext.SaveChangesAsync();
_itemsCursorPagingLoading.OnNext(false);
return;
}