Query SQL in ASP.NET core

public async Task<PagedResult<DocumentsVm>> GetAllByFaculty(GetDocumentsPagingRequest request)
{
    var claimsIdentity = _httpContextAccessor.HttpContext.User.Identity as ClaimsIdentity;
    var userId = claimsIdentity.FindFirst(ClaimTypes.NameIdentifier)?.Value.ToString();
    var query = from d in _context.Documents
                join u in _context.Users on d.UserID equals u.Id
                join p in _context.Positions on u.Id equals p.UserID
                where d.UserID.ToString() == userId 
                select new { d, u,p };
    if (request.DocumentId.HasValue && request.DocumentId.Value > 0)
    {
        query = query.Where(c => c.u.UserName == request.UserName);
    }
    int TotalRow = await query.CountAsync();
    var data = await query.Skip((request.PageIndex - 1) * request.PageSize)
        .Take(request.PageSize)
        .Select(x => new DocumentsVm()
        {
            ID = x.d.ID,
            UserID = x.u.Id,
            UserName = x.u.UserName,
            Caption = x.d.Caption,
            FacultyID = x.d.FacultyOfDocumentID,
            MagazineID = x.d.MagazineID,
            CreateOn = x.d.CreateOn.Date
        }).ToListAsync();
    var pagedResult = new PagedResult<DocumentsVm>()
    {
        TotalRecord = TotalRow,
        Items = data
    };
    return pagedResult;
}