We Keep Coding

Orderby on left join null value

Following situation:
Table of users
Table of addresses
The user has a single optional reference to the address table (=left join)
The query to fetch the data is:
IQueryable<User> query =
from u in _dbContext.Users
join a in _dbContext.Address on u.AddressId equals a.Id into address
from addresses in address.DefaultIfEmpty()
select new User(u, a);
Now I want to do a sorting on the query based on the municipality of the address
query = query.OrderBy(u => u.Address.Municipality);
The problem is that the Address can be a null value (as the address is optional) and for that reason it is throwing following exception.
NullReferenceException: Object reference not set to an instance of an object.
Is there a way to order on the municipality knowing that it can be null?
Already tried following things with same outcome:
query = query.OrderBy(u => u.Address.Municipality ?? "");
query = query.OrderBy(u => u.Address == null).ThenBy(u => u.Address.Municipality);

You can use
query = query.OrderBy(u => u.Address.Municipality.HasValue);

You can write your comparer like this:
public class One
{
public int A { get; set; }
}
public class Two
{
public string S { get; set; }
}
public class T
{
public One One { get; set; }
public Two Two { get; set; }
}
public class OrderComparer : IComparer<Two>
{
public int Compare(Two x, Two y)
{
if (((x == null) || (x.S == null)) && ((y == null) || (y.S == null)))
return 0;
if ((x == null) || (x.S == null))
return -1;
if ((y == null) || (y.S == null))
return 1;
return x.S.CompareTo(y.S);
}
}
static void Main(string[] args)
{
var collection = new List<T> {
new T{ One = new One{A=1}, Two = new Two{ S="dd" } },
new T{ One = new One{A=5}, Two = null },
new T{ One = new One{A=0}, Two = new Two{ S=null } },
new T{ One = new One{A=6}, Two = new Two{ S="aa" } },
};
var comparer = new OrderComparer();
collection = collection.OrderBy(e => e.Two, comparer).ToList();
}
But in your case you have to write var collection = query.AsEnumerable().OrderBy(x=>x.Address).
Also there is other method:
var result = query.Where(x=>x.Address==null || x.Address.Municipality==null)
.Union(query.Where(x.Address!=null && x.Address.Municipality!=null).OrderBy(x=>x.Address.Municipality));

I create a simple demo and it works well when I add nullable foreign key to the two tables.
Besides, I do not understabd what is select new User(u, a); in your code.
Below is my sample code:
Models:
public class User
{
public int Id { get; set; }
public string Name { get; set; }
[ForeignKey("Address")]
public int? AddressId { get; set; }
public Address Address { get; set; }
}
public class Address
{
public int Id { get; set; }
public string AddressName { get; set; }
public string Municipality { get; set; }
}
Action:
IQueryable<User> query =
from u in _context.Users
join a in _context.Address on u.AddressId equals a.Id into address
from addresses in address.DefaultIfEmpty()
select new User
{
Id = u.Id,
Name = u.Name,
AddressId = u.AddressId,
Address = addresses
};
query = query.OrderBy(u => u.Address.Municipality);

Best approach to compare if one list is subset of another in C#

I have the below two classes:
public class FirstInner
{
public int Id { get; set; }
public string Type { get; set; }
public string RoleId { get; set; }
}
public class SecondInner
{
public int Id { get; set; }
public string Type { get; set; }
}
Again, there are lists of those types inside the below two classes:
public class FirstOuter
{
public int Id { get; set; }
public string Name { get; set; }
public string Title { get; set; }
public List<FirstInner> Inners { get; set; }
}
public class SecondOuter
{
public int Id { get; set; }
public string Name { get; set; }
public List<SecondInner> Inners { get; set; }
}
Now, I have list of FirstOuter and SecondOuter. I need to check if FirstOuter list is a subset of SecondOuter list.
Please note:
The names of the classes cannot be changed as they are from different systems.
Some additional properties are present in FirstOuter but not in SecondOuter. When comparing subset, we can ignore their presence in SecondOuter.
No.2 is true for FirstInner and SecondInner as well.
List items can be in any order---FirstOuterList[1] could be found in SecondOuterList[3], based on Id, but inside that again need to compare that FirstOuterList[1].FirstInner[3], could be found in SecondOuterList[3].SecondInner[2], based on Id.
I tried Intersect, but that is failing as the property names are mismatching. Another solution I have is doing the crude for each iteration, which I want to avoid.
Should I convert the SecondOuter list to FirstOuter list, ignoring the additional properties?
Basically, here is a test data:
var firstInnerList = new List<FirstInner>();
firstInnerList.Add(new FirstInner
{
Id = 1,
Type = "xx",
RoleId = "5"
});
var secondInnerList = new List<SecondInner>();
secondInner.Add(new SecondInner
{
Id = 1,
Type = "xx"
});
var firstOuter = new FirstOuter
{
Id = 1,
Name = "John",
Title = "Cena",
Inners = firstInnerList
}
var secondOuter = new SecondOuter
{
Id = 1,
Name = "John",
Inners = secondInnerList,
}
var firstOuterList = new List<FirstOuter> { firstOuter };
var secondOuterList = new List<SecondOuter> { secondOuter };
Need to check if firstOuterList is part of secondOuterList (ignoring the additional properties).

So the foreach way that I have is:
foreach (var item in firstOuterList)
{
var secondItem = secondOuterList.Find(so => so.Id == item.Id);
//if secondItem is null->throw exception
if (item.Name == secondItem.Name)
{
foreach (var firstInnerItem in item.Inners)
{
var secondInnerItem = secondItem.Inners.Find(sI => sI.Id == firstInnerItem.Id);
//if secondInnerItem is null,throw exception
if (firstInnerItem.Type != secondInnerItem.Type)
{
//throw exception
}
}
}
else
{
//throw exception
}
}
//move with normal flow
Please let me know if there is any better approach.

First, do the join of firstOuterList and secondOuterList
bool isSubset = false;
var firstOuterList = new List<FirstOuter> { firstOuter };
var secondOuterList = new List<SecondOuter> { secondOuter };
var jointOuterList = firstOuterList.Join(
secondOuterList,
p => new { p.Id, p.Name },
m => new { m.Id, m.Name },
(p, m) => new { FOuterList = p, SOuterList = m }
);
if(jointOuterList.Count != firstOuterList.Count)
{
isSubset = false;
return;
}
foreach(var item in jointOuterList)
{
var jointInnerList = item.firstInnerList.Join(
item.firstInnerList,
p => new { p.Id, p.Type },
m => new { m.Id, m.type },
(p, m) => p.Id
);
if(jointInnerList.Count != item.firstInnerList.Count)
{
isSubset = false;
return;
}
}
Note: I am assuming Id is unique in its outer lists. It means there will not be multiple entries with same id in a list. If no, then we need to use group by in above query

I think to break the question down..
We have two sets of Ids, the Inners and the Outers.
We have two instances of those sets, the Firsts and the Seconds.
We want Second's inner Ids to be a subset of First's inner Ids.
We want Second's outer Ids to be a subset of First's outer Ids.
If that's the case, these are a couple of working test cases:
[TestMethod]
public void ICanSeeWhenInnerAndOuterCollectionsAreSubsets()
{
HashSet<int> firstInnerIds = new HashSet<int>(GetFirstOuterList().SelectMany(outer => outer.Inners.Select(inner => inner.Id)).Distinct());
HashSet<int> firstOuterIds = new HashSet<int>(GetFirstOuterList().Select(outer => outer.Id).Distinct());
HashSet<int> secondInnerIds = new HashSet<int>(GetSecondOuterList().SelectMany(outer => outer.Inners.Select(inner => inner.Id)).Distinct());
HashSet<int> secondOuterIds = new HashSet<int>(GetSecondOuterList().Select(outer => outer.Id).Distinct());
bool isInnerSubset = secondInnerIds.IsSubsetOf(firstInnerIds);
bool isOuterSubset = secondOuterIds.IsSubsetOf(firstOuterIds);
Assert.IsTrue(isInnerSubset);
Assert.IsTrue(isOuterSubset);
}
[TestMethod]
public void ICanSeeWhenInnerAndOuterCollectionsAreNotSubsets()
{
HashSet<int> firstInnerIds = new HashSet<int>(GetFirstOuterList().SelectMany(outer => outer.Inners.Select(inner => inner.Id)).Distinct());
HashSet<int> firstOuterIds = new HashSet<int>(GetFirstOuterList().Select(outer => outer.Id).Distinct());
HashSet<int> secondInnerIds = new HashSet<int>(GetSecondOuterList().SelectMany(outer => outer.Inners.Select(inner => inner.Id)).Distinct());
HashSet<int> secondOuterIds = new HashSet<int>(GetSecondOuterList().Select(outer => outer.Id).Distinct());
firstInnerIds.Clear();
firstInnerIds.Add(5);
firstOuterIds.Clear();
firstOuterIds.Add(5);
bool isInnerSubset = secondInnerIds.IsSubsetOf(firstInnerIds);
bool isOuterSubset = secondOuterIds.IsSubsetOf(firstOuterIds);
Assert.IsFalse(isInnerSubset);
Assert.IsFalse(isOuterSubset);
}
private List<FirstOuter> GetFirstOuterList() { ... }
private List<SecondOuter> GetSecondOuterList() { ... }

compare 2 properties inside 2 linq lists and return a boolean based on the comparision

I've tried to find the answer to this but nothing seems to fit it quite right.
Requirement: From a known list of FooObjects, return a list of the Foo Id's whose data satisfies all the search criteria.
Here is my code:
class testClass
{
public class SearchItem
{
string Term { get; set; }
decimal Confidence { get; set; }
}
public class FooObject
{
public Guid Id { get; set; }
public List<Data> Data { get; set; }
}
public class Data
{
public string Text { get; set; }
public decimal Confidence { get; set; }
}
[Test]
public void Test()
{
var searchItems = new List<SearchTerm>
{
new SearchTerm{ Confidence = (decimal)1, Term = "TestWord" },
new SearchTerm{ Confidence = (decimal)1, Term = "TestWord2" },
};
var FooObjects = new List<FooObject>
{
new FooObject{Id = new Guid(), Data = new List<Data>
{
new Data{Text = "TestWord", Confidence = 1},
new Data{Text = "TestWord2", Confidence = 1},
new Data{Text = "SomeOtherWord", Confidence = 1},
}
}
};
//result is a list of the Foo IDs
var result = FooObjects.Where(foo => !searchItems.Select(item => item.Term).Except(foo.Data.Select(dt => dt.Text).Distinct()).Any())
.Select(foo => foo.Id).ToList();
Assert.That(result.Count, Is.EqualTo(1));
searchItems.Add(new SearchTerm{Term = "NotFoundString"});
result = FooObjects.Where(foo => !searchItems.Select(item => item.Term).Except(foo.Data.Select(dt => dt.Text).Distinct()).Any())
.Select(foo => foo.Id).ToList();
Assert.That(result.Count, Is.EqualTo(0));
}
}
I now need to modify this so that I can compare against the confidence of each word
Question:
How do I modify the LINQ to compare the confidence and the Term against my data

Instead of matching any criteria like #dymanoid said in his answer, you should be looking to satisfy all the search items/terms (you are mixing these up in your example code, be consistent).
var result = FooObjects
.Where(f => searchItems.All(
s => f.Data.Exists(d => d.Text == s.Term && d.Confidence == s.Confidence)))
.Select(f => f.Id);

Maybe you're looking for something like this:
var result = FooObjects
.Where(foo => foo.Data.Any(d => searchTerms.Any(
si => d.Term == si.Text && d.Confidence == si.Confidence)))
.Select(foo => foo.Id);
Keep in mind that this search isn't effective - if your data sets are large, the performance will be bad.

Left join multiple tables using lambda expression

I have 2 tables:
specs {specId, desc, createdby, lastupdatedby}
users {userid, username}
I want the below linq query need to be written in pure lambda expression
from spec in specs
from user in users.where(x => x.userId== spec.createdby).DefaultIfEmpty()
from updatedUser in users.where(x => x.userId== spec.lastupdatedbyby).DefaultIfEmpty()
select new {
spec = spec
user = user,
updatedUser = updatedUser
}
Please assist.
Data would be like say:
spec[{1, test, 1234, 2345},{2, test1, 1234, null}]
users[{1234, Allen},{2345, Dwayne}]
So the result should be
[{1, test, Allen, Dwayne}, {2, test1, Allen, null}]

Let's start with these classes:
class Specs {
public int specId { get; set; }
public string desc { get; set; }
public int createdby { get; set; }
public int lastupdatedby { get; set; }
}
class Users {
public int userId { get; set; }
public string username { get; set; }
}
class UpdatedUser {
public int userId {get; set;}
public string username { get; set; }
}
Now the Linq query, for convenience I have created some example data:
var specs = new Specs[]
{
new Specs{specId = 1, desc = "Spec1", createdby=1, lastupdatedby=1},
new Specs{specId = 2, desc = "Spec2", createdby=2, lastupdatedby=3},
new Specs{specId = 3, desc = "Spec3", createdby=3, lastupdatedby=1},
new Specs{specId = 4, desc = "Spec4", createdby=3, lastupdatedby=3},
};
var user = new Users[]
{
new Users{userId = 1, username = "User1"},
new Users{userId = 2, username = "User2"},
};
var updatedUser = new UpdatedUser[]
{
new UpdatedUser{userId = 1, username = "UpdatedUser1"},
new UpdatedUser{userId = 2, username = "UpdatedUser2"},
};
var result = specs
.GroupJoin(user,
s => s.createdby,
u => u.userId,
(s, u) => u.Select(x => new {spec = s, user = x})
.DefaultIfEmpty(new {spec = s, user = (Users)null}))
.SelectMany(g => g)
.GroupJoin(updatedUser,
firstJoin => firstJoin.spec.lastupdatedby,
uu => uu.userId,
(firstJoin, uu) =>
uu.Select(y => new {spec = firstJoin.spec, user = firstJoin.user, updatedUser = y})
.DefaultIfEmpty(new {spec = firstJoin.spec, user = firstJoin.user, updatedUser = (UpdatedUser) null}))
.SelectMany(g1 => g1)
.ToList();
The GroupJoin extension method help you obtain a tuple with all the elements of the starting table with a list of elements of the joined table.
Now if you enumerate the results:
result.ForEach(item => {
Console.WriteLine(item.spec.desc);
Console.WriteLine(item.user != null ? item.user.username : "NULL");
Console.WriteLine(item.updatedUser != null ? item.updatedUser.username : "NULL");
Console.WriteLine();
});
You obtain this:
Spec1
User1
UpdatedUser1
Spec2
User2
NULL
Spec3
NULL
UpdatedUser1
Spec4
NULL
NULL

You can try
var list = specs.Join(users,
s => s.lastupdatedby,
u => u.userid,
(s, u) => new { specs = s, users = u })
.Select(x => new {
specId = x.specs.specId,
desc = x.specs.desc,
createdby=x.specs.createdby,
username=x.users.username
}).ToString();

LEFT JOIN MULTIPLE TABLES
------------------------
create table Rama(rid int,name varchar(80),zip int);
create table Kris(kid int,rid int, Title varchar(80),zip int);
insert into Rama values(1,'Robert Rama' ,10001),
(2,'Roger Raju' ,10002),
(3,'Kevin Kali' ,10003),
(4,'Mark Mutu' ,10004)
insert into Kris values(0,0,'NP' ,10001),
(1,1,'VP' ,10001),
(2,2,'AVP',10002)
//Lambda expression
//Download https://www.linqpad.net/Download.aspx
//Create tables as given below and connect linqpad to your db
//select C# statement(s) on linqpad and run below
var v =
from r in Ramas
join k in Kris
on new { r.Rid, r.Zip } equals new { k.Rid, k.Zip }
into resultGroups
from k in resultGroups.DefaultIfEmpty()
select new { r.Rid, r.Name, k.Title };
v.Dump();

ASP.NET MVC 5 Entity Join

I'm new in ASP, Entity and lambda expressions. How can I join two tables?
Route Model:
public partial class Route
{
public Route()
{
Flights = new HashSet<Flight>();
}
public int RouteID { get; set; }
public int DepartureAirportID { get; set; }
public int ArrivalAirportID { get; set; }
public int FlightDuration { get; set; }
public virtual Airport Airport { get; set; }
public virtual Airport Airport1 { get; set; }
public virtual ICollection<Flight> Flights { get; set; }
}
Airport Model:
public partial class Airport
{
public Airport()
{
Routes = new HashSet<Route>();
Routes1 = new HashSet<Route>();
}
public int AirportID { get; set; }
public string City { get; set; }
public string Code { get; set; }
public virtual ICollection<Route> Routes { get; set; }
public virtual ICollection<Route> Routes1 { get; set; }
}
SQL query looks like this:
SELECT a.AirportID, a.City
FROM Route r INNER JOIN Airport a ON r.ArrivalAirportID = a.AirportID
WHERE r.DepartureAirportID = #departureAirportID
ORDER BY a.City
Sorry for this easy question but I don't know how to do this with Entity Framework...

Something like this should do (untested and just going on from your query) with a variable hard-coded):
using (var db = new YourDbContext())
{
var query = from r in db.Route
join a in db.Airport a on r.ArrivalAirportID equals a.AirportID
where r.DepartureAirportID = 1 // replace with your varialble.
orderby a.City
select a;
}

Include with join entity framework. here doctorSendAnswerModel also a inner table.
var data = _patientaskquestionRepository.Table.Include(x=>x.DoctorSendAnswer).Join(_patientRepository.Table, a => a.PatientId, d => d.Id, (a, d) => new { d = d, a = a }).Where(x => x.a.DoctorId == doctorid);
if(!string.IsNullOrEmpty(status))
data=data.Where(x=>x.a.Status==status);
var result = data.Select(x => new {x= x.a,y=x.d }).ToList();
var dt = result.Select(x => new PatientAskQuestionModel()
{
PatientId = x.x.PatientId.Value,
AskQuestion = x.x.AskQuestion,
Id = x.x.Id,
DoctorId = x.x.DoctorId,
FileAttachment1Url = x.x.FileAttachment1,
DocName = x.y.FirstName + " " + x.y.LastName,
CreatedDate = x.x.CreatedDate.Value,
doctorSendAnswerModel = x.x.DoctorSendAnswer.Select(t => new DoctorSendAnswerModel { Answer = t.Answer }).ToList()
}).ToList();
return dt;

LinQ query:
from r in context.Route
join a in context.Airport
on r.ArrivalAirportID equals a.AirportID
WHERE r.DepartureAirportID = "value"
ORDER BY a.City
select a.AirportID, a.City

var balance = (from a in context.Airport
join c in context.Route on a.ArrivalAirportID equals c.AirportID
where c.DepartureAirportID == #departureAirportID
select a.AirportID)
.SingleOrDefault();

You can do the following:
var matches = from a in context.Airports
join r in context.Routes
on a.AirportID equals r.ArrivalAirportID
where r.DepartureAirportID = departureAirportID
order by a.City
select new
{
a.AirportID,
a.City
};

Entity query with conditional join with pagination.
if (pageIndex <= 0)
pageIndex = 1;
pageIndex = ((pageIndex - 1) * pageSize) ;
var patient = _patientRepository.Table.Join(_DoctorPatient.Table.Where(x => x.DoctorId == Id && x.IsBlocked==false), x => x.Id, d => d.PatientId, (x, d) => new { x = x });
if (state != "")
patient = patient.Where(x => x.x.State.Contains(state));
if (name != "")
patient = patient.Where(x => (x.x.FirstName + x.x.LastName).Contains(name));
if (sdate != null)
patient = patient.Where(x => x.x.CreatedDate >= sdate);
if (eDate != null)
patient = patient.Where(x => x.x.CreatedDate <= eDate);
var result = patient.Select(x => x.x).Select(x => new PatientDoctorVM() { PatientId = x.Id, Id = x.Id, FirstName = x.FirstName, LastName = x.LastName, SSN = x.NewSSNNo, UserProfileId = x.UserProfileId, Email = x.Email, TumbImagePath = x.TumbImagePath }).OrderBy(x => x.Id).Skip(pageIndex).Take(pageSize).ToList();

Your entity and lembda query will be lool like this:
return (from d in _doctorRepository.Table
join p in _patientDoctor.Table on d.Id equals p.DoctorId
where p.PatientId == patientid.Value select d
).ToList();

Take a look at this site, it will explain you how the join works in Linq.
So if you ever need it again you will be able to solve it yourself.