I have come across a problem with a query where I'm trying to sort the result by descending but it doesn't do it. I have gone through few posts on stackoverflow with similar issue but none of the solutions seemed to work. I was wondering if someone could point out what is wrong with my code. Heres part of the query relevant to a problem:
from followup in ctx.FollowUps
.Where(f => f.DestEntityId == user.Id
&& f.DestEntityType == (int)ContactEntityTypeEnum.User)
.OrderByDescending(x => x.AddDate)
select new
{
user = new { Firstname = user.Firstname },
followup = new { followup.NextFollowUpDate }
});
I also tried adding .ToList() before .OrderByDescending() but that didn't solve the problem either.
Following up the comments from #SILENT & #D.Shih your Linq expression is looking a bit odd.
var followUps = ctx.FollowUps
.Where(f => f.DestEntityId == user.Id
&& f.DestEntityType == (int)ContactEntityTypeEnum.User)
.OrderByDescending(x => x.AddDate)
.Select(x => new
{
UserFirstname = user.Firstname,
AddDate = x.AddDate,
FollowupDate = x.NextFollowUpDate
}).ToList();
This will order the results by AddDate, not NextFollowUpDate, so I've added AddDate to the output just to avoid confusion between the two, since I don't know how you'd have assessed that they weren't in order based on only seeing the NextFollowUpDate. I don't recommend mixing the LinQL (from/where/select) with the Fluent methods. (above)
There doesn't look to be a point in returning each individual property in a separate anonymous type, just flatten it into a single package since anonymous types are intended for short lives and immediate consumption.
Related
I have a LINQ query retrieving a list of , such as this:
var results = SearchContext.GetQueryable<Person>()
.Where(i => i.Enabled)
.Where(i => i.TemplateName == "Person")
.Random(6);
Each object of type "Person" has a "Location" field which is also a Glass mapped item, and hence has an ID; I would like to only select items whose Location has a specific ID.
How can I go about doing this in an efficient manner?
EDIT: I should probably clarify that I am unable to perform this comparison, efficiently or not. Because the GUID is an object and I cannot perform ToString in a LINQ query, I am unable to only pick the items whose Location item has a specific ID. Any clues on how this could be achieved?
EDIT 2: Adding the clause
.Where(i => i.Location.Id == this.Id)
Doesn't work, for... some reason, as I'm unable to debug what LINQ "sees". If I convert the other ID I'm comparing it against to string this way:
var theOtherID = this.Id.ToString("N");
Then it works with this LINQ line:
.Where(i => i["Location"].Contains(theOtherID))
I still have no idea why.
One approach is to include a separate property on Person that is ignored by Glass mapper, but can be used in searches:
[SitecoreIgnore]
[Sitecore.ContentSearch.IndexField("location")]
public Sitecore.Data.ID LocationID { get; set; }
You can use this in your search as follows:
Sitecore.Data.ID locationId = Sitecore.Data.ID.Parse(stringOrGuid);
var results = SearchContext.GetQueryable<Person>()
.Where(i => i.Enabled)
.Where(i => i.TemplateName == "Person")
.Where(i => i.LocationID == locationId)
.Random(6);
I think the efficiency of using multiple where clauses vs. conditionals is debatable. They will likely result in the same Lucene query being performed. I would prefer readability over optimization in this instance, but that's just me.
I can't think of a more efficient methods than using a simple where statement like in:
var results = SearchContext.GetQueryable<Person>()
.Where(i => i.Enabled && i.TemplateName == "Person" &&
i.Location != null && i.Location.Id == 1)
.Random(6);
Keep in mind that if you use the && statement instead of a where for each parameter, you reduce the complexity of the algorithm.
You could also use an Inverse Navigation Property on Location to a virtual ICollection<Person> and then be able to do this:
var results = SearchContext.GetQueryable<Location>()
.Where(i => i.Id == 1 && i.Persons.Where(p => p.Enabled && p.TemplateName == "Person").Any())
.Random(6);
The first option would still be the most efficient, because the second one uses sub-queries. But it is worth knowing you can do your search the other way.
I have got a bit of an issue and was wondering if there is a way to have my cake and eat it.
Currently I have a Repository and Query style pattern for how I am using Linq2Sql, however I have got one issue and I cannot see a nice way to solve it. Here is an example of the problem:
var someDataMapper = new SomeDataMapper();
var someDataQuery = new GetSomeDataQuery();
var results = SomeRepository.HybridQuery(someDataQuery)
.Where(x => x.SomeColumn == 1 || x.SomeColumn == 2)
.OrderByDescending(x => x.SomeOtherColumn)
.Select(x => someDataMapper.Map(x));
return results.Where(x => x.SomeMappedColumn == "SomeType");
The main bits to pay attention to here are Mapper, Query, Repository and then the final where clause. I am doing this as part of a larger refactor, and we found that there were ALOT of similar queries which were getting slightly different result sets back but then mapping them the same way to a domain specific model. So take for example getting back a tbl_car and then mapping it to a Car object. So a mapper basically takes one type and spits out another, so exactly the same as what would normally happen in the select:
// Non mapped version
select(x => new Car
{
Id = x.Id,
Name = x.Name,
Owner = x.FirstName + x.Surname
});
// Mapped version
select(x => carMapper.Map(x));
So the car mapper is more re-usable on all areas which do similar queries returning same end results but doing different bits along the way. However I keep getting the error saying that Map is not able to be converted to SQL, which is fine as I dont want it to be, however I understand that as it is in an expression tree it would try to convert it.
{"Method 'SomeData Map(SomeTable)' has no supported translation to SQL."}
Finally the object that is returned and mapped is passed further up the stack for other objects to use, which make use of Linq to SQL's composition abilities to add additional criteria to the query then finally ToList() or itterate on the data returned, however they filter based on the mapped model, not the original table model, which I believe is perfectly fine as answered in a previous question:
Linq2Sql point of retrieving data
So to sum it up, can I use my mapping pattern as shown without it trying to convert that single part to SQL?
Yes, you can. Put AsEnumerable() before the last Select:
var results = SomeRepository.HybridQuery(someDataQuery)
.Where(x => x.SomeColumn == 1 || x.SomeColumn == 2)
.OrderByDescending(x => x.SomeOtherColumn)
.AsEnumerable()
.Select(x => someDataMapper.Map(x));
Please note, however, that the second Where - the one that operates on SomeMappedColumn - will now be executed in memory and not by the database. If this last where clause significantly reduces the result set this could be a problem.
An alternate approach would be to create a method that returns the expression tree of that mapping. Something like the following should work, as long as everything happening in the mapping is convertible to SQL.
Expression<Func<EntityType, Car>> GetCarMappingExpression()
{
return new Expression<Func<EntityType, Car>>(x => new Car
{
Id = x.Id,
Name = x.Name,
Owner = x.FirstName + x.Surname
});
}
Usage would be like this:
var results = SomeRepository.HybridQuery(someDataQuery)
.Where(x => x.SomeColumn == 1 || x.SomeColumn == 2)
.OrderByDescending(x => x.SomeOtherColumn)
.Select(GetCarMappingExpression());
Consider the following Query :
var profilelst =
(
from i in dbContext.ProspectProfiles
where i.CreateId == currentUser
select new ProspectProfile
{
ProspectId = i.ProspectId,
Live = i.Live,
Name = i.Name,
ServiceETA = i.Opportunities.OrderByDescending(t => t.FollowUpDate)
.FirstOrDefault()
.ServiceETA.ToString(),
FollowUpDate = i.Opportunities.OrderByDescending(t => t.FollowUpDate)
.FirstOrDefault()
.FollowUpDate
}
)
.ToList();
return profilelst.OrderByDescending(c=>c.FollowUpDate)
.Skip(0).Take(endIndex)
.ToList();
Here in this query please take a look at FollowUpDate and ServiceType, these both i have fetched from Opportunity table, is there any other work around to get these both..
One to Many Relationship in tables is like: ProspectProfile -> Opportunities
Whether the query i have written is ok or is there any another work around that can be done in easier way.
The only thing you can improve is to avoid ordering twice by changing your code to this:
var profilelst
= dbContext.ProspectProfiles
.Where(i => i.CreateId == currentUser)
.Select(i =>
{
var opportunity
= i.Opportunities
.OrderByDescending(t => t.FollowUpDate)
.First();
return new ProspectProfile
{
ProspectId = i.ProspectId,
Live = i.Live,
Name = i.Name,
ServiceETA = opportunity.ServiceETA.ToString(),
FollowUpDate = opportunity.FollowUpDate
}
}).ToList();
return profilelst.OrderByDescending(c => c.FollowUpDate).Take(endIndex).ToList();
I made several changes to your original query:
I changed it to use method chains syntax. It is just so much easier to read in my opinion.
I removed the unnecessary Skip(0).
The biggest change is in the Select part:
I changed FirstOrDefault to First, because you are accessing the properties of the return value anyway. This will throw a descriptive exception if no opportunity exists. That's better than what you had: In your case it would throw a NullReferenceException. That's bad, NullReferenceExceptions always indicate a bug in your program and are not descriptive at all.
I moved the part that selects the opportunity out of the initializer, so we need to do the sorting only once instead of twice.
There are quite a few problems in your query:
You cannot project into an entity (select new ProspectProfile). LINQ to Entities only supports projections into anonymous types (select new) or other types which are not part of your entity data model (select new MySpecialType)
ToString() for a numeric or DateTime type is not supported in LINQ to Entities (ServiceETA.ToString())
FirstOrDefault().ServiceETA (or FollowUpdate) will throw an exception if the Opportunities collection is empty and ServiceETA is a non-nullable value type (such as DateTime) because EF cannot materialize any value into such a variable.
Using .ToList() after your first query will execute the query in the database and load the full result. Your later Take happens in memory on the full list, not in the database. (You effectively load the whole result list from the database into memory and then throw away all objects except the first you have Takeen.
To resolve all four problems you can try the following:
var profilelst = dbContext.ProspectProfiles
.Where(p => p.CreateId == currentUser)
.Select(p => new
{
ProspectId = p.ProspectId,
Live = p.Live,
Name = p.Name,
LastOpportunity = p.Opportunities
.OrderByDescending(o => o.FollowUpDate)
.Select(o => new
{
ServiceETA = o.ServiceETA,
FollowUpDate = o.FollowUpDate
})
.FirstOrDefault()
})
.OrderByDescending(x => x.LastOpportunity.FollowUpDate)
.Skip(startIndex) // can be removed if startIndex is 0
.Take(endIndex)
.ToList();
This will give you a list of anonymous objects. If you need the result in a list of your entity ProspectProfile you must copy the values after this query. Note that LastOpportunity can be null in the result if a ProspectProfile has no Opportunities.
If I have a query that looks like this:
var forms = repo.GetForms().Where(f => f.SubForms.Any(sf => sf.Classes.Any(c => c.TermId == termId)));
From this you can see my schema is as follows:
SubForm has many Class which has many Term.
What I want:
All SubForms with their Classes In a particular Term.
What is happening now is that I get all the SubForm that has any Class in a particular Term. That means that SubForm comes back with ALL child Class and not just the ones related to the Term.
For eg. I have 2 terms, a subform with 2 classes in each term. This query brings back 4 classes instead of the 2 in that particular term.
Is there any Include('Expression') that I can use to say that I only want to include all classes based on a condition? Or is my query wrong?
Use this:
var subForms = repo.GetSubForms.Select(sf = new {
SubForm = sf,
Classes = sf.Classes.Where(c => c.TermId == termId)
}).ToList()
.Select(t => t.SubForm)
.ToList();
UPDATE: based on #Slauma's comment:
If you want to load SubForms that they have any Class that has a Term by termId, you can go from end to begin; like this:
var subForms = repo.Terms.Where(t => t.Id == termId).Select(t => new {
Term = t,
Class = t.Class,
SubForm = t.Class.SubForm
}).ToList()
.Select(t => t.SubForm).ToList();
OR in a easiest way, you can use Include on your Term, see:
var subForms = repo.Terms.Include("Class.SubForm").Where(t => t.Id == termId)
.Select(t => t.Class.SubForm).ToList();
NOTE: As I can understand from your question, you have a relationship like this:
SubForm has_many Class has_many Term
But, your provided code is showing a relationship like this one:
SubForm has_many Class
Term has_many Class
If you can, put your entities in question, or explain their relationship more please. Thank you.
An Include(Where Expression) does not exist. If you use eager loading with Include you will always load all the elements.
There is a way around this by using projections. The basic idea is you will select a new anonymous type with the property you want and another property with the filtered navigational items. EF will link those together and as a result you will fake a Include(Where ... )
Check this for an example.
You know sometimes I start getting lost in fancy LINQ extension methods and attempting to figure out how to eagerly load exactly what I want and resort to a very simple "join" concept.
var result =
(from f in SubForums
from c in Classes
from t in Term
where t.TermId = 1
select new { SubForum = f, Class = c, Term = t }).ToList();
This is a simple join that uses predefined navigation properties (hence you don't have to specify the join condition). You return an anonymous type with everything that you need. The beauty of this is that Entity Framework will do the auto-fixup for you, therefor you're free to return the SubForum only from your method if you wish, it will automatically contain the Class and subsequent Term references.
I don't know the exact names of the relations, but it should be something along the lines of
repo.Terms
.Include("Classes")
.Include("Classes.SubForms")
.SingleOrDefault(x => x.TermId = termId);
// or
repo.GetSubForms
.Include("Classes")
.Where(sf => sf.Classes.Where(c => c.TermId == termId));
This seems to be a common request, it was difficult to find a solution to it when I was looking earlier this year. I ended up using the solution included in the link below (I'm not sure this is the exact solution I found, but it's the same idea). Hope this helps!
Filter the "Includes" table on Entity Framework query
//Found this method to filter our child objects instead of using .include()
var Results = (from res in
(from u in DataContext.User
where u.Type.ToUpper() != "ADMIN"
&& u.StartDate <= DateTime.Now
&& (u.EndDate == null || u.EndDate >= DateTime.Now)
select new
{
User = u,
Access = u.Access.Where(a => a.StartDate <= DateTime.Now
&& (a.EndDate == null || a.EndDate >= DateTime.Now))
}
)
select res);
//The ToArray is neccesary otherwise the Access is not populated in the Users
ReturnValue = Results.ToArray().Select(x => x.User).ToList();
After some advice on how to do this nicely using lambda expressions.
What I want is to get a list of placements based on an agency. I want the placements where the placement.agency != agency but where placement.agencypersonnel contains any of the agency staff.
So where the placement is not for that agency, but there are staff from that agency involved in another agency's placement
I don't know how to query based on the second condition.
So something like:
// agency is being passed in
var agencySupervisors = agency.AgencyPersonnel;
return agency.Placements
.Where(p => p.Supervisors.Contains(agencySupervisors))
.Where(p => p.Agency != agency);
I get that Contains is supposed to refer to a single object rather than a collection - which is why its erroring.. but I'm not sure how to get it to check against all objects in the collection.
Have also tried Any
return agency.Placements
.Where(p => agencySupervisors.Any<PlacementSupervisor>(p.Supervisors))
.Where(p => p.Agency != agency);
So hopefully its just I'm using the wrong one!!
Another spanner in the works is trying to figure out how the placement supervisor and the agency personnel entities relate to one another.. I think its linked on AgencyPersonnelId = SupervisorId so I'm guessing that will also have to be factored into my expression.
Thanks!
Edit: How do I handle if the type of objects in the two list aren't the same - but I know that the Id will match. Do I have to write a comparer and somehow incorporate that into the expression?? ie. AgencyPersonnelId = SupervisorId
I have tried:
return placements
.Where(p => p.Supervisors.Any(supervisor => agencySupervisors.Any(ap => ap.AgencyPersonnelId == supervisor.SupervisorId)));
But it is giving me no results so it is obviously wrong.
Edit: Actually when I try to iterate through the placements in the returned collection I'm getting a null reference exception - so I'm not sure if its something to do with my expression or the way I'm returning the results.
You are close with Any & Contains - try both at once
return agency.Placements
.Where(p => agencySupervisors.Any(supervisor => p.Supervisors.Contains(supervisor))
.Where(p => p.Agency != agency);
I think you can do it with .Intersect also:
return agency.Placements
.Where(p => agencySupervisors.Intersect(p.Supervisors).Any()
&& p.Agency != agency);
Thanks everyone for the help - Because the objects were of different types I ended up having to do something a little different - but then found I was able to use their Ids for the comparison so the result was:
var agencySupervisors = (from ap in agency.AgencyPersonnel
where ap != null
select ap.AgencyPersonnelId).ToList();
return
(from p in m_PlacementRepository.Linq orderby p.PlacementId select p)
.Where(p => p.Agency != agency)
.Where(p => p.Supervisors != null && p.Supervisors.Any(s => agencySupervisors.Contains(s.SupervisorId)));
Plus as Mikael rightly pointed out I was starting with the wrong collection in the first place :)