I have a query that gets data in the form of an IQueryable
var assys = assetrelationshipRepository.GetAll()
.Where(x => x.AssetId == siteAssetId)
.Where(x => x.RelationshipTypeId == (long)AssetRelationshipTypeEnum.Parent)
.Where(x => x.RelatedAsset.AssetTypeId == (long)AssetTypeEnum.Assembly)
.Select(x => x.RelatedAsset.CustomAssetAttributes2);
For every 'assy' that is returned, I'd like to get it's AssetId and use this to get a list of 'subassys', see below. For each 'assy' record, the assyId variable should be substituted for its AssetId.
var subassys = assetrelationshipRepository.GetAll()
.Where(x => x.AssetId == assyId)
.Where(x => x.RelationshipTypeId == (long)AssetRelationshipTypeEnum.Parent)
.Where(x => x.RelatedAsset.AssetTypeId == (long)AssetTypeEnum.SubAssy)
.Select(x => x.RelatedAsset.CustomAssetAttributes2);
I assume I'll need to use ForEach, does anyone know if what I'm trying to do is possible?
Thanks
Applying ForEach would be extremely bad approach to retrieve your desired result. You could apply join and group for that queries instead.
var assysQuery = assetrelationshipRepository.GetAll()
.Where(x => x.AssetId == siteAssetId)
.Where(x => x.RelationshipTypeId == (long)AssetRelationshipTypeEnum.Parent)
.Where(x => x.RelatedAsset.AssetTypeId == (long)AssetTypeEnum.Assembly);
Then apply join and group;
var subAssysQuery =
from assy in assysQuery
join subAssy in assetrelationshipRepository.GetAll() on assy.Id equals subAssy.AssetId
where
subAssy.RelationshipTypeId == (long)AssetRelationshipTypeEnum.Parent &&
subAssy.RelatedAsset.AssetTypeId == (long)AssetTypeEnum.Assembly
group assy by assy.Id into g
select new
{
AssyId = g.Key,
SubAssets = g.Select(x => x.RelatedAsset.CustomAssetAttributes2),
};
This should give you CustomAssetAttributes2 value of subassys for per assy record.
Note : Also, I suggest you to use known type for select clause instead
of anonymous type.
Related
I want to filter the IQueryable<T> with the help of EF.Functions.Like() method, which accepts a string parameter, to make use of array of strings. Also, I want this filter to be applied on an IQueryable and not on a List.
var configurations = _dbContext.Configurations
.Include(x => x.ChildTable)
.Where(x => x.Id == Id);
if (!string.IsNullOrEmpty(request.Filter))
{
configurations = configurations.Where(x => EF.Functions.Like(string.Join(", ", x.ChildTable.Select(x => x.Name).ToArray()), '%' + request.Filter + '%'));
}
In the above code, Configuration has a one-many relationship with the ChildTable. Meaning, each configuration will have a more than one ChildTable entries related. So, with that given, x.ChildTable.Select(x => x.Name) is of type IEnumerable<string>. And, I want to filter the Configuration records whose ChildTable.Name entries is like the given request.Filter.
Try the following query:
var configurations = _dbContext.Configurations
.Include(x => x.ChildTable)
.Where(x => x.Id == Id);
if (!string.IsNullOrEmpty(request.Filter))
{
configurations = configurations
.Where(x => x.ChildTable.Any(c => EF.Functions.Like(c.Name, '%' + request.Filter + '%')));
}
This query was working fine before we upgraded:
var appUsers = await _masterDbContext
.Users
.Include(x => x.UserCustomers)
.AsNoTracking()
.Select(AppUserDto.Projection)
.Where(user => !user.IsDeleted && user.UserCustomers.Any(x => x.CustomerId == tenant.Id && x.UserId == user.Id))
.DistinctBy(x => x.Id)
.ToDataSourceResultAsync(request.GridOptions, cancellationToken: cancellationToken);
We're now getting the error:
Either rewrite the query in a form that can be translated,
or switch to client evaluation explicitly by inserting a call to 'AsEnumerable',
'AsAsyncEnumerable', 'ToList', or 'ToListAsync'.
It appears that the DistinctBy is the offender but being fairly new to LINQ I can't figure out how to rewrite it so that it works.
Change DistinctBy to Distinct() and move that and the predicate before the Select. I also shifted the AsNoTracking() up:
var appUsers = await _masterDbContext
.Users
.AsNoTracking()
.Include(x => x.UserCustomers)
.Where(user =>
!user.IsDeleted
&& user.UserCustomers
.Any( x => x.CustomerId == tenant.Id ) )
.Distinct()
.Select(AppUserDto.Projection)
.ToDataSourceResultAsync(request.GridOptions, cancellationToken: cancellationToken);
Looks you have upgraded from EF Core 2.x, which loads full filtered set into the memory. DistinctBy is not translatable by EF Core 6.
Try the following solution:
var filtered = _masterDbContext.Users
.Select(AppUserDto.Projection)
.Where(user => !user.IsDeleted && user.UserCustomers.Any(x => x.CustomerId == tenant.Id && x.UserId == user.Id));
var query =
from d in filtered.Select(d => new { d.Id }).Distinct()
from u in filtered.Where(u => u.Id == d.Id).Take(1)
select u;
var appUsers = await query.ToDataSourceResultAsync(request.GridOptions, cancellationToken: cancellationToken);
In this EF query, for the contacts list, I'm trying to query to get records for ContactTypeA and populate results in contacts list. If there are no records for ContactTypeA, then I want it to query for records for ContactTypeB and populate results in contacts list. I tried to use DefaultIfEmpty but that method only accepts single value and not a list. 'contacts' is a List object. Any ideas or even an alternative to DefaultIfEmpty? Thanks.
select(i => new transaction{
....
contacts = contactRepository.All.Where(c => c.AccountId == i.Account.Id && contactTypeRepository.All.Any(ct => ct.ContactId == c.Id && ct.Type == ContactType.ContactTypeA)).ToList().DefaultIfEmpty((contactRepository.All.Where(c => c.AccountId == i.Account.Id && contactTypeRepository.All.Any(ct => ct.ContactId == c.Id && ct.Type == ContactType.ContactTypeB)).ToList()
}
)
Firstly, make absolutely sure your contactRepository.All() method returns IQueryable<Contact> and not IEnumerable<Contact>, IList<Contact> or the like, otherwise you are automatically loading all contacts into memory.
From there, don't be afraid to simplify your query across multiple statements to make it a lot easier to understand. You should also leverage navigation properties rather than relying on completely disconnected entities and generic repositories and manually joining these all up in huge expressions.
Ideally an Account could have a collection of Contacts, but if not, at a minimum a Contact should have ContactType references:
var accountContactsQuery = contactRepository.All
.Where(c => c.AccountId == i.AccountId); //Remains IQueryable
var contacts = accountContactsQuery
.Where(c => c.ContactTypes.Any(ct => c.Type == ContactType.ContactTypeA)
.ToList(); // Gets List of Contacts where contains at least 1 ContactTypeA type.
// If we have none, replace with results for ContactTypeB
if (!contacts.Any())
contacts = accountContactsQuery
.Where(c => c.ContactTypes.Any(ct => c.Type == ContactType.ContactTypeB)
.ToList();
This looked a bit odd in that your ContactType appears to have a ContactId, (As opposed to Contact containing a ContactTypeId?) But the above reflects the relationship in your example.
With Account containing Contacts collection:
var accountContactsQuery = accountRepoitory.All
.Where(a => true /* replace with relevant criteria */);
var contacts = accountContactsQuery
.SelectMany(a => a.Contacts)
.Where(c => c.ContactTypes.Any(ct => c.Type == ContactType.ContactTypeA)
.ToList(); // Gets List of Contacts where contains at least 1 ContactTypeA type.
// If we have none, replace with results for ContactTypeB
if (!contacts.Any())
contacts = accountContactsQuery
.SelectMany(a => a.Contacts)
.Where(c => c.ContactTypes.Any(ct => c.Type == ContactType.ContactTypeB)
.ToList();
When dealing with conditions in expressions, I can suggest returning all relevant details, then building your final "payload" based on the conditions.
For example, if querying accounts to build transactions but wanting to load ContactAs if available and Bs for each account if not available:
var transactionData = accountRepoitory.All
.Where(a => true /* replace with relevant criteria */);
.Select(a => new
{
a.AccountId,
/* populate account and common details.. */
ContactAs = a.Contacts
.Where(c => c.ContactTypes.Any(ct => c.Type == ContactType.ContactTypeA).ToList(), // Consider a Select to get relevant details...
ContactBs = a.Contacts
.Where(c => c.ContactTypes.Any(ct => c.Type == ContactType.ContactTypeB).ToList()
}).ToList(); // Executes query against DB to load relevant data...
var transactions = transactionData
.Select( t => new Transaction
{
AccountId = t.AccountId,
/* Other fields */
Contacts = t.ContactAs.Any() ? t.ContactAs : t.ContactBs
}).ToList();
Essentially use the EF Linq expressions to load the possible data, so include results for both ContactA and ContactB, then afterwards build your final projection using that data and conditionally use the ContactA or B as suited. Generally I don't advise passing Entities back (Actual Contact entities) but project into minimally viable view models in the first EF query using Select.
Using Entity Framework Core 2.2 I have the following query:
var user = await context.Users.AsNoTracking()
.Include(x => x.Lessons).ThenInclude(x => x.LessonLevel)
.FirstOrDefaultAsync(x => x.Id == userId);
var lessons = context.Lessons.AsNoTracking();
.Where(x => x.LessonLevelId < user.Lessons.Max(y => y.LessonLevelId));
Thus query evaluates locally and I get the message:
The LINQ expression 'Max()' could not be translated and will be evaluated locally.'
How can I make this query evaluate on the server?
Update
Based on DavigG answer I made it work using:
var maxLessonLevelId = user.Lessons.Max(y => y.LessonLevelId););
var lessons = context.Lessons.AsNoTracking();
.Where(x => x.LessonLevelId < maxLessonLevelId);
I know the following evaluates locally but shouldn't evaluate on the server?
var lessons = context.Lessons.AsNoTracking();
.Where(x => x.LessonLevelId <
context.Users.AsNoTracking()
.Where(y => y.Id == userId)
.Select(y => y.Lessons.Max(z => z.LessonLevelId))
.FirstOrDefault());
Is it possible to use a child queries that evaluates on the server?
Get the max value as a separate query, for example:
var maxLessonLevelId = user.Lessons.Max(y => y.LessonLevelId);
Then you can can get the lessons like this:
var lessons = context.Lessons.AsNoTracking()
.Where(x => x.LessonLevelId < maxLessonLevelId);
I am trying to select a list of objects at the end of a fairly long chain of joins/selects using Linq to Entities written as Lambda Expressions... Here is what I have currently the following two statements.
var formDefId = _unitOfWork.AsQueryableFor<FormTrack>()
.Where(x => x.FormTrackId == formTrackId)
.Select(x => x.FormDefId).First();
var rules = _unitOfWork.AsQueryableFor<FormTrack>()
.Where(x => x.FormTrackId == formTrackId)
.Select(x => x.FormDef)
.SelectMany(x => x.Events
.Where(y => y.EventTypeId == 7))
.Select(x => x.RuleGroup)
.SelectMany(x => x.Rules)
.SelectMany(x => x.RuleFormXmls
.Where(y => y.FormDefId == formDefId));
What I would like to do, is combine the two queries, and use the FormDefId returned by
.Select(x => x.FormDef)
in the final where clause instead of having to use the formDefId from a separate query.
Is this something that is possible?
Thank you in advance for your help
It is much easier to write this using query syntax.. Each from in query syntax corresponds to a SelectMany in lambda syntax. This allows you to have all the variables in scope.
var rules =
from ft in _unitOfWork.AsQueryableFor<FormTrack>()
from e in ft.FormDef.Events
from r in e.RuleGroup.Rules
from x in r.RuleFormXmls
where ft.FormTrackId == formTrackId
where e.EventTypeId == 7
where x.FormDefId == ft.FormDefId
select x