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Add a list of objects to DTO create in entity framework c#

I have the following code in my c# controller,
[HttpGet("antifungal/{name}")]
public List<DrugInteractionDTO> test(string name)
{
var DI = (from D1 in _context.DrugInteractions
join D2 in _context.DrugInteractionReferences
on D1.ID equals D2.DrugInteractionId into joined
from D3 in joined.DefaultIfEmpty()
where D1.AntifungalAgent.Name.ToLower().Contains(name.ToLower())
select new DrugInteractionDTO
{
Severity = D1.Severity,
SeverityAsString = D1.Severity.ToString(),
ProDetailedInformation = D1.ProDetailedInformation,
BasicDetailedInformation = D1.BasicDetailedInformation,
Antifungal = D1.AntifungalAgent.Name,
InteractingDrug = D1.InteractingDrug.GenericName,
ID = D1.ID,
Count = 2
//DrugInteractionReferences
}).ToList();
return DI.OrderBy(x => x.InteractingDrug).ToList();
}
My DrugInteractionDTO model has a field List<DrugInteractionReferences> which I want to add to.
my two tables are interactions and references each interaction can have many references.
I'm used to using Java (Spring) and I can't figure out how to return the references that belong to each interaction in the DTO. The current application I am helping on is very old and has many many problems.
Is it possible to add the list of references to each interactionDTO which is being created in this code?

It is called Eager Loading query, detail entities should be retrieved not by join but subquery expression:
var DI = (from D1 in _context.DrugInteractions
where D1.AntifungalAgent.Name.ToLower().Contains(name.ToLower())
select new DrugInteractionDTO
{
Severity = D1.Severity,
SeverityAsString = D1.Severity.ToString(),
ProDetailedInformation = D1.ProDetailedInformation,
BasicDetailedInformation = D1.BasicDetailedInformation,
Antifungal = D1.AntifungalAgent.Name,
InteractingDrug = D1.InteractingDrug.GenericName,
ID = D1.ID,
Count = 2,
DrugInteractionReferences = _context.DrugInteractionReferences
.Where(D2 => D2.DrugInteractionId == D1.ID)
.ToList()
}).ToList();
If you encounter performance issues, add .AsSplitQuery() before last .ToList()

entity framwork core generates weird sql

I have an existing LINQ query that I am trying to optimize. I have the following entity Types (simplified)
public class Account
{
public int Id { get; set; }
public IEnumerable<OpportunityInfo> Opportunities { get; set; }
}
public class Opportunity
{
public int Id { get; set; }
public string Name { get; set; }
public bool Active { get; set; }
public IEnumerable<Quote> Quotes { get; set; }
}
public class Quote
{
}
It is a standard hierarchy of Account to Opportunity to Quote. Nothing Special. I have the following query that I am using on an ASP.NET Core controller index method. I am starting from Quote and working backwards because there is dynamic query logic between the query and opportunityQuotes that must be Quote based. Otherwise I would start from the top direction.
var query = from o in Quotes select o;
additional query logic (filtering and sorting)
var opportunityQuotes = from o in query
group o by new
{
accountId = o.Opportunity.AccountId,
accountName = o.Opportunity.Account.Name,
active = o.Opportunity.Account.Active,
}
into p
select new
{
Id = p.Key.accountId,
Name = p.Key.accountName,
Active = p.Key.active,
Opportunities =
(from q in p
group q by new
{
Id = q.Opportunity.Id,
Name = q.Opportunity.Name,
Active = q.Opportunity.Active
}
into r
select new
{
Name = r.Key.Name,
Id = r.Key.Id,
Active = r.Key.Active,
Quotes = r
})
};
opportunityQuotes.Dump();
This query generates the following SQL.
SELECT [o].[Id], [o].[ARRValue], [o].[AccountId], [o].[AdjustedArr], ...
FROM [Quotes] AS [o]
LEFT JOIN [Opportunities] AS [o.Opportunity] ON [o].[OpportunityId] = [o.Opportunity].[Id]
INNER JOIN [Accounts] AS [o.Account] ON [o].[AccountId] = [o.Account].[Id]
ORDER BY [o].[AccountId], [o.Account].[Name], [o.Account].[Active]
GO
SELECT [q.Opportunity0].[Id], [q.Opportunity0].[Name], [q.Opportunity0].[Active]
FROM [Opportunities] AS [q.Opportunity0]
GO
SELECT [q.Opportunity0].[Id], [q.Opportunity0].[Name], [q.Opportunity0].[Active]
FROM [Opportunities] AS [q.Opportunity0]
GO
SELECT [q.Opportunity0].[Id], [q.Opportunity0].[Name], [q.Opportunity0].[Active]
FROM [Opportunities] AS [q.Opportunity0]
GO
In reality it generates on query for each opportunity, but I left that out for brevity sake. In my opinion EF should not generate a separate query for each quote. In fact if I comment out the .Name and .Active key parameters in the query as shown below:
group q by new
{
Id = q.Opportunity.Id,
// Name = q.Opportunity.Name,
// Active = q.Opportunity.Active
}
and comment out the correspond variables in the select clause it generates much cleaner sql.
SELECT [o].[Id], [o].[ARRValue], [o].[AccountId], ...
FROM [Quotes] AS [o]
LEFT JOIN [Opportunities] AS [o.Opportunity] ON [o].[OpportunityId] = [o.Opportunity].[Id]
INNER JOIN [Accounts] AS [o.Account] ON [o].[AccountId] = [o.Account].[Id]
ORDER BY [o].[AccountId], [o.Account].[Name], [o.Account].[Active]
GO
The reason I am confused is that .Name and .Active are in the exact same object, they are grouped in the key in the same way as the .Id field, and therefore I don't see why EF would change its behavior just by adding additional group values. Can someone explain the behavior?

Let's take a step back and look at it from a different perspective: If you were to write the SQL query manually, and wanted to fetch all the data required in one query, you would get a lot of duplicate data for the opportunities and account. You could also do this here:
var query = from o in Quotes select o;
var oppQuotes = from o in query
select new
{
AccountId = o.Opportunity.Account.Id,
AccountName = o.Opportunity.Account.Name,
// ... and so on, with all the fields you expect to use.
OpportunityId = o.Opportunity.Id,
OpportunityName = o.Opportunity.Name,
// ... and so on, with all the fields you expect to use.
QuoteId = o.Id,
QuoteName = o.Name,
// ... and again, you get the point.
};
Then, just do an .AsEnumerable() on it, and perform the grouping in your C# code. The database won't be able to optimize anything anyways.
var opportunityQuotes = from q in oppQuotes.AsEnumerable()
group q by new { q.AccountId, q.AccountName }
into accounts
// ... and so on.
For your question, why EF is creating the strange query, I'm at a loss.
In any case, it is always good to be thinking about how YOU would create the sql code to get the data you want most efficiently and not rely on EF to "do the right thing". In many cases it will, in others it will completely blow up in your face. When you want a query, think of the SQL and then translate that to EF code. If you tell it specifically, what you want, you will get it.

How do I map multiple lists with dapper

I've got three classes User, Order & Project which are stored in single tables. The orders and projects both have a n:n relation with the users.
To implement that I've got two crosstables (UserOrders, UserProjects) which map these relations.
public class User
{
public string UserID {get;set;}
public List<string> Orders{get;set;}
public List<string> Projects {get;set;}
}
public class Order
{
public string OrderID {get;set}
...
}
public class Project
{
public string ProjectID {get;set}
...
}
As you can see the User object contains a list of every related orderID/projectID.
Now I want to query this with Dapper. I' ve got this solution which works pretty fine with one list. But if I try to query the complete user object for the 2nd list I'll get every result multiplied with the number of results in the first list.
So if a user got 3 orders and 2 projects the orderlist will be fine and the projectlist will contain both projects 3 times:
var lookup = new Dictionary<string, User>();
var multi = dbDapperFM.Query<User, string, string, User>("SELECT u.*, uo.OrderID, up.ProjectID "+
"FROM User u INNER JOIN UserOrders uo ON u.UserID=uo.UserID "+
"INNER JOIN UserProjects up ON u.UserID=up.UserID", (u, uo, up) =>
{
User user;
if (!lookup.TryGetValue(m.UserID, out user))
lookup.Add(u.UserID, user= u);
if (user.Orders == null)
user.Orders = new List<string>();
user.Orders.Add(uo);
if (user.Projects == null)
user.Projects = new List<string>();
user.Projects.Add(up);
return user;
}, splitOn: "UserID , OrderID, ProjectID ").AsQueryable();
I understand why this problem occures (2 inner joins), but I don't really get how to solve it.

I also had trouble coming to grips with the fact that Dapper doesn't do this automatically.
First, I'm not sure about comma-separated values for "splitOn." I thought you could only have one value there. So I have multiple columns in my result set named "ID" for example.
Second, to get the proper 1:N relationships you need to do an extra manual step. For example, I did a 2-table join of participants and their phone numbers. Then I had to do this:
private List<Participant> CollapseResultSet(List<Participant> rawdataset)
{
List<Participant> ret = new List<Participant>();
if (!rawdataset.Any())
{
return ret;
}
else
{
List<string> partIds = rawdataset.Select(p => p.ID).Distinct().ToList();
foreach (string pId in partIds)
{
Participant tmp = rawdataset.Where(p => p.ID == pId).FirstOrDefault();
tmp.PhoneNumbers = rawdataset.Where(p => p.ID == pId).Select(n => n.PhoneNumbers[0]).ToList();
ret.Add(tmp);
}
return ret;
}
}
Hope that helps.

LINQ aggregate multiple tables

I have the following database. A list of companies. Each company has multiple employees and multiple contractors.
dbo.Companies (CompanyId, Name)
dbo.Employees (Id, CompanyId, Name ...)
dbo.Contractors(Id, CompanyId, Name...)
I want to get output like so
CompanyName #Employees #Contractors
abc 0 10
xyz 25 999
I am trying to avoid doing 2 queries, one to get contractors and one to get employees and then merging them. Is there a way to get it done in one go?
n.b. i have
class CompanySummary{
string Name {get; set;}
int EmpCount {get; set;}
int ConCount {get; set;}
}
so I can use a collection of this type as result

If you have defined navigation properties (and if you haven't, may be it's a good time to do that), the query should be quite simple:
var query = from c in db.Companies
select new CompanySummary
{
Name = c.Name,
EmpCount = c.Employees.Count(),
ConCount = c.Contractors.Count(),
};
Of course you can do that manually, but the above is the preferred way with EF:
var query = from c in db.Companies
select new CompanySummary
{
Name = c.Name,
EmpCount = db.Employees.Count(e => e.CompanyId == c.Id),
ConCount = db.Contractors.Count(cc => cc.CompanyId == c.Id),
};
In both cases you'll get a single SQL query.

If you are using Entity Framework to communicate with the database and have the tables linked with foreign keys you can probably do it in one query. It would look something like this:
IEnumerable<CompanySummary> companySummary = null;
using (CompanyEntities dbContext = new CompanyEntities())
{
companySummary = dbContext.Companies
.Include(company => company.Employees)
.Include(company => company.Contractors)
.Select(company => new CompanySummary
{
Name = company.Name,
EmpCount = company.Employees.Count(),
ConCount = company.Contractors.Count()
});
}

Linq to entities - SQL Query - Where list contains object with 2 properties (or more)

Having the following example:
var myIds = db.Table1.Where(x=>x.Prop2 == myFilter).Select(x=>x.Id).ToList();
var results = db.Table2.Where(x=> myIds.Contains(x.T1)).ToList();
This part is straight forward.
However, now I am facing a "slight" change where my "filter list" has 2 properties instead of only one:
// NOTE: for stackoverflow simplification I use a basic query to
// get my "myCombinationObject".
// In reality this is a much more complex case,
// but the end result is a LIST of objects with two properties.
var myCombinationObject = db.Table3.Where(x=>x.Prop3 == myFilter)
.Select(x=> new {
Id1 = x.T1,
Id2 = x.T2
}).ToList();
var myCombinationObjectId1s = myCombinationObject.Select(x=>xId1).ToList();
var myCombinationObjectId2s = myCombinationObject.Select(x=>xId2).ToList();
// step#1 - DB SQL part
var resultsRaw = db.Tables.Where( x=>
myCombinationObjectId1s.Contains(x.Prop1)
|| myCombinationObjectId2s.Contains(x.Prop2))
.ToList();
// step#2 - Now in memory side - where I make the final combination filter.
var resultsFiltered = resultsRaw.Where( x=>
myCombinationObject.Contains(
new {Id1 = x.Prop1, Id2 = x.Prop2 }
).ToList();
My question: is it even possible to merge the step#2 in the step#1 (query in linq to entities) ?

I've managed once to do what you want, however it is pretty hard and requires changing entity model a bit. You need an entity to map type
new {Id1 = x.Prop1, Id2 = x.Prop2 }
So you need enity having 2 properties - Id1 and Id2. If you have one - great, if not then add such entity to your model:
public class CombinationObjectTable
{
public virtual Guid Id1 { get; set; }
public virtual Guid Id2 { get; set; }
}
Add it to your model:
public DbSet<CombinationObjectTable> CombinationObjectTable { get; set; }
Create new migration and apply it database (database will have now additional table CombinationObjectTable). After that you start to build a query:
DbSet<CombinationObjectTable> combinationObjectTable = context.Set<CombinationObjectTable>();
StringBuilder wholeQuery = new StringBuilder("DELETE * FROM CombinationObjectTable");
foreach(var obj in myCombinationObject)
{
wholeQuery.Append(string.Format("INSERT INTO CombinationObjectTable(Id1, Id2) VALUES('{0}', '{1}')", obj.Id1, obj.Id2);
}
wholeQuery.Append(
db.Tables
.Where( x=>
myCombinationObjectId1s.Contains(x.Prop1)
|| myCombinationObjectId2s.Contains(x.Prop2))
.Where( x=>
combinationObjectTable.Any(ct => ct.Id1 == x.Id1 && ct.Id2 == x.Id2)
).ToString();
);
var filteredResults = context.Tables.ExecuteQuery(wholeQuery.ToString());
Thanks to this your main query stays written in linq. If you do not want to add new table to your db this is as well achievable. Add new class CombinationObjectTable to model, generate new migration to add it and afterwards remove code creating that table from migration code. After that apply migration. This way the db schema won't be changed but EF will think that there is CombinationObjectTable in database. Instead of it you will need to create a temporary table to hold data:
StringBuilder wholeQuery = new StringBuilder("CREATE TABLE #TempCombinationObjectTable(Id1 uniqueidentifies, Id2 uniqueidentifier);");
And when you invoke ToString method on your linq query change CombinationObjectTable to #TempCombinationObjectTable:
...
.ToString()
.Replace("CombinationObjectTable", "#TempCombinationObjectTable")
Other thing worth considering would be using query parameters to pass values in INSERT statements instead of just including them in query yourself - this is of course achievable with EF as well. This solution is not fully ready to apply, rather some hint in which direction you may go for the solution.

Can you do something like this:
var result=
db.Tables
.Where(t=>
db.Table3
.Where(x=>x.Prop3 == myFilter)
.Any(a=>a.T1==t.Prop1 || a.T2==t.Prop2)
).ToList();

If you simply want to avoid the intermediate result (and also creating a second intermediary list) you can do the following
var resultsFiltered = db.Tables.Where( x=>
myCombinationObjectId1s.Contains(x.Prop1)
|| myCombinationObjectId2s.Contains(x.Prop2))
.AsEnumerable() // everything past that is done in memory but isn't materialized immediately, keeping the streamed logic of linq
.Where( x=>
myCombinationObject
.Contains(new {Id1 = x.Prop1, Id2 = x.Prop2 })
.ToList();