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Multiple data query with LINQ

I have a function to get data from my database with join on it. I want to take data from different tables, how can I achieve this? I want to take "libelle_motif" which is from the table "motif_deplacement"
My function right now:
public static List<personne> getPersonne_Deplacement(int numDeplacement)
{
List<personne> desP = new List<personne>();
var query = (from Per in db.personne.ToList()
join Dep in db.deplacement_personne.ToList() on Per.num_personne equals Dep.num_personne
join Mot in db.motif_deplacement.ToList() on Dep.id_motif equals Mot.id_motif
where Dep.id_deplacement == numDeplacement
select new personne
{
nom_personne = Per.nom_personne,
num_personne = Per.num_personne,
ref_personne = Per.ref_personne,
libelle_motif = Mot.libelle_motif,
});
desP = query.ToList();
return desP;
}
And this is how my database looks like :

You will have to create a new class which will act as the model with the properties you want. Construct one of those in your select based on the included relationships.
Also it much easier to manage this query if you model your relationships in your EF entities as opposed to writing out join statements in every query.
Also notice that I removed all the calls to ToList. Your previous code was materializing all entities from each table and then joining and filtering in memory which is extremely inefficient.
public static List<SomeModel> getPersonne_Deplacement(int numDeplacement)
{
var query = from Per in db.personne
join Dep in db.deplacement_personne on Per.num_personne equals Dep.num_personne
join Mot in db.motif_deplacement on Dep.id_motif equals Mot.id_motif
where Dep.id_deplacement == numDeplacement
select new SomeModel
{
nom_personne = Per.nom_personne,
num_personne = Per.num_personne,
ref_personne = Per.ref_personne,
libelle_motif = Mot.libelle_motif,
};
return query.ToList();
}
SomeModel.cs
public class SomeModel
{
public string nom_personne {get;set;}
public string num_personne {get;set;}
public string ref_personne {get;set;}
public string libelle_motif {get;set;}
// add additional properties as needed
}

I don't know if my answer is related to your question. But why don't you use .Include()
Ex:
var result = db.personne.Include(x => x.deplacement_personne).ThenInclude(x => x.motif_deplacement)
It will give you this structure:
obj personne { nom_personne, ... , obj deplacement_personne { ... , obj motif_deplacement }
You can also select any cols with .Select() , or filter it with .Where().

Query Entity Framework using C# and Navigation Properties

First of all I am new to both C# and EF.
I have created a number of entities with the the Model designer in VS 2015 CE and set the relationships.
I would like to query the entities to return all the customers for a specific Contract (e.g. Contract_ID = 1), along with related properties from the CustomerLocker and ContractCustomer entities (For the CustomerLocker Entity if they are present, or null if they are not). I also have the LockerNumber value from the Contract entity (e.g. 100).
I would be grateful if someone can help with the LINQ query required to select the properties I require. I would prefer to be able to use navigation properties if possible.
So far I am able to select the customers but not able to select properties from the CustomerLocker entity.
var myCustomers = (from cc in context.ContractCustomers
where cc.Contract_ID.Equals(contractID)
select new
{
Licencee = cc.IsLicencee,
Added = cc.AddedDate,
Firstname = cc.Customer.FirstName,
Lastname = cc.Customer.LastName,
DOB = cc.Customer.DateOfBirth,
Postcode = cc.Customer.PostCode,
CustomerNumber = cc.CustomerNumber
}
)
entities shown in VS Model Designer

You could get the HasCard from CustomerLockers by filtering on LockerNumber;
CustomerLockers = cc.Customer.CustomerLockers
The query;
var myCustomers = (from cc in context.ContractCustomers
where cc.Contract_ID.Equals(contractID)
select new
{
Licencee = cc.IsLicencee,
Added = cc.AddedDate,
Firstname = cc.Customer.FirstName,
Lastname = cc.Customer.LastName,
DOB = cc.Customer.DateOfBirth,
Postcode = cc.Customer.PostCode,
CustomerNumber = cc.CustomerNumber,
CustomerLockerHasCard = cc.Customer.CustomerLockers
.Where(x => x.LockerNumber == 1000)
.Select(x => x.HasCard)
}
)
Also, I suggest you to define model classes as known type instead of using anonymous type.

An option would be to get the list of customers instead of just the customer's number :
var myCustomers = (from cc in context.ContractCustomers
where cc.Contract_ID.Equals(contractID)
select new
{
Licencee = cc.IsLicencee,
Added = cc.AddedDate,
Firstname = cc.Customer.FirstName,
Lastname = cc.Customer.LastName,
DOB = cc.Customer.DateOfBirth,
Postcode = cc.Customer.PostCode,
CustomerNumber = cc.CustomerNumber,
listOfCustomers = cc.Customer.ToList() // <-Here, a list
}
)
Then you can use a loop :
foreach(var customer in myCustomers.listOfCustomers)
{
var listOfLockers = customer.CustomerLockers.ToList();
}
But this is more a beginner's way, remember it's always better to take everything you need in a single query, like Stormcloack's answer.
This answer is just to show you how you can dig in the entitys the easy way.

Search method joing multiple tables

I need help with a search method for searching the tables for a matching text.
This works, except that the join needs to be LEFT OUTER JOIN otherwise I dont get any results if the pageId is missing in any of the tables.
This solution takes to long time to run, I would appreciate if someone can help me out with a better solution to handle this task.
public async Task<IEnumerable<Result>> Search(string query)
{
var temp = await (from page in _context.Pages
join pageLocation in _context.PageLocations on page.Id equals pageLocation.PageId
join location in _context.Locations on pageLocation.LocationId equals location.Id
join pageSpecialty in _context.PageSpecialties on page.Id equals pageSpecialty.PageId
join specialty in _context.Specialties on pageSpecialty.SpecialtyId equals specialty.Id
where
page.Name.ToLower().Contains(query)
|| location.Name.ToLower().Contains(query)
|| specialty.Name.ToLower().Contains(query)
select new Result
{
PageId = page.Id,
Name = page.Name,
Presentation = page.Presentation,
Rating = page.Rating
}).ToListAsync();
var results = new List<Result>();
foreach (var t in temp)
{
if (!results.Exists(p => p.PageId == t.PageId))
{
t.Locations = GetLocations(t.PageId);
t.Specialties = GetSpecialties(t.PageId);
results.Add(t);
}
}
return results;
}

Using navigation properties, the query could look like:
var temp = await (from page in _context.Pages
where Name.Contains(query)
|| page.PageLocation.Any(pl => pl.Location.Name.Contains(query))
|| page.PageSpecialties.Any(pl => pl.Specialty.Name.Contains(query))
select new Result
{
PageId = page.Id,
Name = page.Name,
Presentation = page.Presentation,
Rating = page.Rating,
Locations = page.PageLocation.Select(pl => pl.Location),
Specialties = page.PageSpecialties.Select(pl => pl.Specialty)
}).ToListAsync();
This has several benefits:
By the absence of joins, The query returns unique Result objects right away, so you don't need to deduplicate them afterwards.
The locations and specialties are loaded in the same query instead of two queries per Result (aka n+1 problem).
(Likely) ToLower is removed because the search is probably not case sensitive anyway. The query is executed as SQL and most of the times, SQL databases have case-insensitive collations. Removing ToLower makes the query sargable again.

Fetch distinct object from a collection using GroupBy on a single column in LINQ to Objects/SQL/Entity

I have a Database table Country with example data as follows:
CountryId CountryName Year
1 UK 2001
2 UK 2003
3 UK 2004
4 USA 2001
5 USA 2005
I have a GetAllCountries() method on my DataAccessLevel:
public static IEnumerable<Country> GetAllCountries()
{
List<Country> countries;
using (var context = new ReportEntities())
{
countries= (from c in context.Countries
select c).ToList();
}
return countries;
}
That should return a list of Country objects which I can then use to bind a DropdDownList to show data. When I bind I use the to pick specific attributes to display from the object. So where I need List so that later I can use it in different data loading methods. For example in LoadCountriesToDdlList():
{
var countries= _transactionService.GetAllCountries();
var distinctcountries = countries.GroupBy(c=> c.CountryName);
_UIDDListCountries.DataSource = distinctcountries ;
}
Expected result for the list:
CountryName
UK
USA
I have tried lot of different ways to edit the query but failed every time. Any ideas?
Tried: GrouppBy, OrderedBy, Distinct(), selecting new object, but no luck. The problem seem that I am trying to return a list of Objects.

If you just want the dropdown to have Distinct country name from the above table you could try the below:
{
var countries= _transactionService.GetAllCountries();
var distinctcountries = countries.GroupBy(c=> c.CountryName);
_UIDDListCountries.DataSource = distinctcountries.Select(g => g.First());
}
The above code first groups all the countries objects based on CountryName and then we assign only the first object of each grouped result to the dropdown datasource.
If you want to customize your text field value you could create an anonymous type and use it. Code below:
{
var countries= _transactionService.GetAllCountries();
var distinctcountries = countries.GroupBy(c=> c.CountryName);
_UIDDListCountries.DataSource = distinctcountries.Select(g => new { CountryID = g.First().CountryID, CountryName = g.First().CountryName ,Text = String.Concat(g.First().CountryName, "--", g.First().Year) }) ;
_UIDDListCountries.DataTextField = "Text";
_UIDDListCountries.DataValueField = "CountryName";
}
NOTE: This works when you are only concerned about showing distinct values of CountryNames in the dropdown and not considering the CountryID and the Year in any case

It sounds like you want this
countries= (from c in context.Countries
select c.CountryName).Distinct()

GroupBy() should give you what you're after:
var grouped = context.Countries.GroupBy(c => c.CountryName);
foreach (var country in grouped)
{
var distinctCountryName = country.Key; //Access field used to group
var firstMatchingCountry = country.First();
var matchingCountriesInAList = country.ToList();
}

You could use the following if only country name matters...as in countryId and year don't.
//Note, you'll probably want to change this function name because it's
//not actually getting all countries anymore
public static IEnumerable<Country> GetAllCountries()
{
using (var context = new ReportEntities())
{
//Note, this LINQ query can also return an IQueryable. This is useful
//if you're querying a database because you'll be doing more logic in SQL
//and transferring less data from your database to memory on your C# machine
IEnumerable<Country> countries =
from c in context.Countries
group c by c.CountryName into countriesGroupedByName
select countriesGroupedByName.First();
return countries;
}
}
Do something like the following if you care about countryId and countryName.
IEnumerable<Country> countries =
from c in context.Countries
group c by c.CountryName into countriesGroupedByName
select countriesGroupedByName.OrderBy(c => c.CountryId).First();

How can I query this hierarchical data using LINQ?

I have 3 kinds of objects: Agency, BusinessUnit and Client (each with their own respective table)
In terms of hierarchy, Agencies own BusinessUnits, and BusinessUnits own Clients.
I have 3 C# POCO Objects to represent them (I usually select new {} into them, rather than use the LINQ generated classes):
public class Agency
{
public IEnumerable<BusinessUnit> BusinessUnits { get; set; }
}
public class BusinessUnit
{
public IEnumerable<Client> Clients { get; set; }
}
public class Client
{
public int NumberOfAccounts { get; set; }
public Decimal AmountOfPlacement { get; set; }
public Decimal AvgBalance { get; set; }
public Double NeuPlacementScore { get; set; }
}
You can see that Agencies contain a list of BusinessUnits, and BusinessUnits contain a list of Clients.
I also have a mapping table called BAC_Map in the database which says which owns which, and it looks something like this:
How can I construct a query, so I can query for and return a list of Agencies? Meaning that, I want each Agency to have its list of BusinessUnit objects set, and I want the list of BusinessObjects to have its list of Clients set.
I can do basic LINQ queries, but this is a little over my head concerning the Map table and the multiple? queries.
How could I construct a method like GetAllAgencies() which would query, for not only all agencies, but populate its BusinessUnits that Agency owns, and the Clients those BusinessUnits own?
Edit: Any tips or info is appreciated. Do I need to do joins? Does this need to be multiple queries to return an Agency list, with its submembers populated?

If you drop all four tables (Agency, BusinessUnit, Client, Map) on the linq to sql designer, and draw relationships from Map to the other three, there will be some useful properties on Map.
//construct a query to fetch the row/column shaped results.
var query =
from m in db.map
//where m.... ?
let a = m.Agency
let b = m.BusinessUnit
let c = m.Client
// where something about a or b or c ?
select new {
AgencyID = a.AgencyID,
AgencyName = a.Name,
BusinessUnitID = b.BusinessUnitID,
ClientID = c.ClientID,
NumberOfAccounts = c.NumberOfAccounts,
Score = c.Score
};
//hit the database
var rawRecords = query.ToList();
//shape the results further into a hierarchy.
List<Agency> results = rawRecords
.GroupBy(x => x.AgencyID)
.Select(g => new Agency()
{
Name = g.First().AgencyName,
BusinessUnits = g
.GroupBy(y => y.BusinessUnitID)
.Select(g2 => new BusinessUnit()
{
Clients = g2
.Select(z => new Client()
{
NumberOfAccounts = z.NumberOfAccounts,
Score = z.Score
})
})
})
.ToList();
If approriate filters are supplied (see the commented out where clauses), then only the needed portions of the tables will be pulled into memory. This is standard SQL joining at work here.

I created your tables in a SQL Server database, and tried to recreate your scenario in LinqPad. I ended up with the following LINQ statements, which basically result in the same structure of your POCO classes:
var map = from bac in BAC_Maps
join a in Agencies on bac.Agency_ID equals a.Agency_ID
join b in BusinessUnits on bac.Business_Unit_ID equals b.Business_Unit_ID
join c in Clients on bac.Client_ID equals c.Client_ID
select new
{
AgencyID = a.Agency_ID,
BusinessUnitID = b.Business_Unit_ID,
Client = c
};
var results = from m in map.ToList()
group m by m.AgencyID into g
select new
{
BusinessUnits = from m2 in g
group m2 by m2.BusinessUnitID into g2
select new
{
Clients = from m3 in g2
select m3.Client
}
};
results.Dump();
Note that I called map.ToList() in the second query. This actually resulted in a single, efficient query. My initial attempt did not include .ToList(), and resulted in nine separate queries to produce the same results. The query generated by the .ToList() version is as follows:
SELECT [t1].[Agency_ID] AS [AgencyID], [t2].[Business_Unit_ID] AS [BusinessUnitID], [t3].[Client_ID], [t3].[NumberOfAccounts], [t3].[AmountOfPlacement], [t3].[AvgBalance], [t3].[NeuPlacementScore]
FROM [BAC_Map] AS [t0]
INNER JOIN [Agencies] AS [t1] ON [t0].[Agency_ID] = [t1].[Agency_ID]
INNER JOIN [BusinessUnits] AS [t2] ON [t0].[Business_Unit_ID] = [t2].[Business_Unit_ID]
INNER JOIN [Clients] AS [t3] ON [t0].[Client_ID] = [t3].[Client_ID]
Here is a screenshot of the results:
alt text http://img411.imageshack.us/img411/5003/agencybusinessunitclien.png

If you are doing this with direct LINQ to SQL, there is no way to do this without some kind of recursion, whether you do it yourself or you hide it behind an extension method. Recursive SQL is very bad (many round trips, many single queries).
There are two options here. One is to pull the entire table(s) with the hierarchy into memory and use LINQ to Objects on it. Leave the "details" tables in SQL. If you have less than several thousand entities, this is probably the most efficient way to go. You can keep a single copy of the table(s) in cache and refresh them when necessary. When you need to fetch more detailed data from the DB for a single record, you can reattach that entity from your cached hierarchy to a new DataContext and fetch it.
The other option is to use a more complex relationship model in your database. Storing parent only by nature demands recursion, but you can use the adjacency list model to construct a single query which can span many levels of inheritance. This will mean your LINQ to SQL queries become less intuitive (querying against Entity.Right and Entity.Left isn't quite as pretty as Parent or Children...) but you can do in one query what might take hundreds or thousands in the literal recursive approach.