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Using where in LINQ select new statement for specific columns

I'm working on a class assignment and got a bit lost in LINQ.
I have 3 tables, 'oltandok' contains the data of persons, 'preferenciak' contains the preferred vaccine of that person with 3 columns:
an FK for table oltandok
a number indicating the order of preferences (1 is highest, 6 is lowest preferred)
an FK for another table containing the data on the vaccines called 'vakcinak'
I would like to display the data in a DataGridView the following way:
Personal data and the preferred vaccines in different columns:
Pref1 - Name of the vaccine where pref == 1
Pref2 - Name of the vaccine where pref == 2
etc.
This is where I am with my code, but I'm not sure how to select the preferences properly.
manu_rogz.DataSource = ( from x in context.oltandok
join y in context.preferencia on x.TAJ equals y.oltandok_FK
select new
{
TAJ = x.TAJ,
Nev = x.nev,
Szuletesnap = x.birthdate,
Pref1 = ???
Pref2 = ???
}
).ToList();

Because the preferenciak table contains multiple rows per person, you will need to perform some grouping.
Here is some very rough code which illustrates one way to do that.
using System;
using System.Collections.Generic;
using System.Linq;
class Program
{
static void Main(string[] args)
{
var persons = new List<Person> { new Person { ID = 11, PersonName = "Alice" }, new Person { ID = 22, PersonName = "Bob" } };
var vaccines = new List<Vaccine> { new Vaccine(){ ID = 111, VaccineName= "Pfizer" }, new Vaccine(){ ID = 222, VaccineName = "Moderna" } };
var preferences = new List<VaccPref>
{
new VaccPref() { Person_FK = 11, Preference = 1, Vaccine_FK = 111 },
new VaccPref() { Person_FK = 11, Preference = 2, Vaccine_FK = 222 },
new VaccPref() { Person_FK = 22, Preference = 1, Vaccine_FK = 222 },
new VaccPref() { Person_FK = 22, Preference = 2, Vaccine_FK = 111 }
};
var prefsWithVaccNames = preferences.Join(vaccines, p => p.Vaccine_FK, v => v.ID, (pref, vaccine) => new Tuple<VaccPref, string>(pref, vaccine.VaccineName));
var groupedPrefs = prefsWithVaccNames.GroupBy(p => p.Item1.Person_FK);
var personPrefs = new List<PersonPrefs>();
foreach (var group in groupedPrefs)
{
personPrefs.Add(
new PersonPrefs()
{
Person_FK = group.Key,
Pref1 = group.Single(v => v.Item1.Preference == 1).Item2,
Pref2 = group.Single(v => v.Item1.Preference == 2).Item2,
});
}
var personPrefsWithPersonNames =
personPrefs.Join(
persons,
pp => pp.Person_FK,
p => p.ID,
(pp, p) => new NamedPersonPrefs() { Name = p.PersonName, Pref1 = pp.Pref1, Pref2 = pp.Pref2 }).ToArray();
}
}
class Person
{
public int ID { get; set; }
public string PersonName { get; set; }
}
class VaccPref
{
public int Person_FK { get; set; }
public int Preference { get; set; }
public int Vaccine_FK { get; set; }
}
class Vaccine
{
public int ID { get; set; }
public string VaccineName { get; set; }
}
class PersonPrefs
{
public int Person_FK { get; set; }
public string Pref1 { get; set; }
public string Pref2 { get; set; }
}
class NamedPersonPrefs
{
public string Name { get; set; }
public string Pref1 { get; set; }
public string Pref2 { get; set; }
}
This is a self-contained C# program which should produce a result similar to what you're after. You will of course need to adjust the class definitions (and change the table names) to suit your needs.
I've used LINQ's fluent syntax but you can use the SQL-like version if you prefer.

Is there a way to append a calculated field to Select()?

Is there a way to add a field to an IQueryable (or List<> or whatever) without having to rewrite an entire "new {list, of, all, fields}". I have a dynamic field who can have different formulas depending on the situation. Here's a basic example :
public class User
{
public string FirstName { get; set; }
public string LastName { get; set; }
}
List<User> users = new List<User>();
users.Add(new User { FirstName = "Foo", LastName = "Bar"} );
users.Add(new User { FirstName = "Bar", LastName = "Foo"} );
I would like to add a field later ( just before the output ) without removing or rewriting all the existing fields
var betterUser = users.Select(u => new { FullName = u.FirstName + " " + u.LastName });
This will only return FullName, but I want to keep FirstName and LastName. In my real code, I have about 15 fields and about 1.2 billion rows that will be cleaned up before adding the last field so if I add all possible calculated fields directly to the model, the performance takes a serious hit.

You could do something like this
public class User
{
public string FirstName { get; set; }
public string LastName { get; set; }
public object dynamicField {get; set;}
}
List<User> users = new List<User>();
users.Add(new User { FirstName = "Foo", LastName = "Bar"} );
users.Add(new User { FirstName = "Bar", LastName = "Foo"} );
foreach (var obj in users)
{
obj.dynamicField = obj.FirstName + " " + obj.LastName;
}
This way you would not have to remove or rewrite all the existing fields.

Your user class needs a property to do this: but you can do it:
public class Animal
{
public string Name { get; set; }
public bool HasLegs { get; set; }
public bool IsFoo { get; set; }
public string FooLegs { get; set; }
}
private static string legsString(bool hasLegs)
{
return hasLegs ? "Has Legs" : "Has No Legs";
}
static void Main(string[] args)
{
List<Animal> animals = new List<Animal>()
{
new Animal()
{
Name = "Foo",
HasLegs = true
},
new Animal()
{
Name = "Kangaroo",
HasLegs = true
},
new Animal()
{
Name = "Snake",
HasLegs = false
}
};
var fooAnimals = animals.Select(s => new Animal
{
Name = s.Name,
HasLegs = s.HasLegs,
IsFoo = (s.Name == "Foo" && s.HasLegs),
FooLegs = $"{s.Name} {legsString(s.HasLegs)}"
}).AsQueryable<Animal>();
}
}

C# - Adding data to list inside list

How can I add the following data on the table into a list called Vehicles?
public class criterias
{
public double values { get; set; }
public double time { get; set; }
}
public class movChannels
{
public string name { get; set; }
public IList<criterias> criteria = new List<criterias>();
}
public class stepsList
{
public string steps { get; set; }
public IList<movChannels> stepChannelsCriteria = new List<movChannels>();
}
public class vehicles
{
public int vehID { get; set; }
public string vehDescription { get; set; }
public IList<stepsList> vehValCriteria = new List<stepsList>();
}
Now, how can I add the data that I have in the table shown into a list called Vehicles? I will create other vehicles later...

You had several bad decisions, some were design flaws and some were minor C# naming convention violations.
Couple of worth mentions flaws:
vehID should have been a string and not int (Example "XPT")
Movment has Name, Value and Time. It doesn't have a list of Values and Times.
Creation:
List<Vehicle> vehicles = new List<Vehicle>();
Vehicle vehicle = new Vehicle()
{
Id = "XPT",
Description = "Average Car",
Steps = new List<Step>()
{
new Step() {
Name = "move car",
Movements = new List<Movement>()
{
new Movement("engage 1st gear", 1, 1),
new Movement("reach 10kph", 10, 5),
new Movement("maintain 10kph", 10, 12),
}
},
new Step() {
Name = "stop car",
Movements = new List<Movement>()
{
new Movement("reach 0kph", 10, 4),
new Movement("put in neutral", 0, 1),
new Movement("turn off vehicle", 0, 0),
}
}
}
};
vehicles.Add(vehicle);
Entities:
public class Movement
{
public string Name { get; set; }
public double Values { get; private set; }
public double Time { get; private set; }
public Movement(string name, double values, double time)
{
Name = name;
Values = values;
Time = time;
}
}
public class Step
{
public string Name { get; set; }
public IList<Movement> Movements { get; set; }
}
public class Vehicle
{
public string Id { get; set; } // Should be changed to string
public string Description { get; set; }
public IList<Step> Steps { get; set; }
}

You should create your classes like the following:
public class criterias
{
public double values { get; set; }
public double time { get; set; }
}
public class movChannels
{
public movChannels
{
criteria = new List<criterias>();
}
public string name { get; set; }
public IList<criterias> criteria { get; set; }
}
public class stepsList
{
public stepsList
{
stepChannelsCriteria = new List<movChannels>();
}
public string steps { get; set; }
public IList<movChannels> stepChannelsCriteria { get; set; }
}
public class vehicles
{
public vehicles
{
vehValCriteria = new List<stepsList>();
}
public int vehID { get; set; }
public string vehDescription { get; set; }
public IList<stepsList> vehValCriteria { get; set; }
public movChannels movments { get; set; }
}

What about that?
public class VehiclesViewModel
{
public List<vehicles> Vehicles { get; private set; }
public void Initalize()
{
this.Vehicles = new List<vehicles>();
var vehicle = new vehicles
{
vehID = 1,
vehDescription = "firstDescription",
};
var stepsList = new stepsList
{
steps = "firstStep",
};
var movChannel = new movChannels
{
name = "firstChannel",
};
var criteria = new criterias
{
values = 0.5,
time = 0.5
};
movChannel.criteria.Add(criteria);
stepsList.stepChannelsCriteria.Add(movChannel);
vehicle.vehValCriteria.Add(stepsList);
this.Vehicles.Add(vehicle);
}
}

it seems in your table the VehicleId is of type string. Make sure your VehicleId property in Vehicle class also matches the same.
You can use the collection initializers to set the values of child objects like this way:
var data = new vehicles()
{
vehID = 1,
vehDescription = "Average Car",
vehValCriteria = new List<stepsList>()
{
new stepsList()
{
steps = "Move car",
stepChannelsCriteria = new List<movChannels>()
{
new movChannels()
{
name = "engage firstgear",
criteria = new List<criterias>()
{
new criterias()
{
values = 1,
time = 1
},
}
},
new movChannels()
{
name = "reach 10kph",
criteria = new List<criterias>()
{
new criterias()
{
values = 10,
time = 5
},
}
},
new movChannels()
{
name = "maintain 10kph",
criteria = new List<criterias>()
{
new criterias()
{
values = 10,
time = 12
},
}
}
}
},
new stepsList()
{
steps = "stop car",
stepChannelsCriteria = new List<movChannels>()
{
new movChannels()
{
name = "reach okph",
criteria = new List<criterias>()
{
new criterias()
{
values = 10,
time = 4
},
}
},
new movChannels()
{
name = "put in neutral",
criteria = new List<criterias>()
{
new criterias()
{
values = 0,
time = 1
},
}
},
new movChannels()
{
name = "turn off vehicle",
criteria = new List<criterias>()
{
new criterias()
{
values = 0,
time = 0
},
}
}
}
}
}
};

You can fill your list by moving from top to bottom, like
Create Criterias List then Create movChannel object and add that list
to Criterias object and so on
However if you want to avoid this way, there is another way. If you are using Linq To List then follow this
Get a simple flat object to a list object
var TableData = db.Tablename.Tolist();
Then fill your own object like this
Vehicles finalList = TableData.Select(a => new Vehicles()
{
vehID = a.Id,
vehDescription = a.des,
vehValCriteria = TableData.Where(b => b.StepslistId == a.StepslistId)
.Select(c => new StepsList()
{
steps = c.Steps,
stepChannelsCriteria = TableData.Where(d => d.channelId == c.channelId)
.select(e => new MovChannels()
{
name = e.name,
criteria = TableData.Where(f => f.criteriasId = e.criteriasId)
.Select(g => new Criterias()
{
values = g.Values,
time = g.Time
}).ToList()
}).ToList()
}).ToList()
}).ToList();
This is standard way to fill list within list

How to use condition for all children in Entity Framework

I have these classes:
public class product
{
public int Id { get; set; }
public string Title { get; set; }
public Store Store { get; set; }
public ICollection<Color> Colors { get; set; }
}
public class Color
{
public int Id { get; set; }
public string Name { get; set; }
public product Product { get; set; }
}
public class Store
{
public int Id { get; set; }
public string Name { get; set; }
public string City { get; set; }
public ICollection<product> Products { get; set; }
}
And I have this list :
List<Store> Stores = new List<Store>
{
new Store { Id = 1, Name = "Lilo", City = "Teh",
Products = new List<product>
{
new product
{ Id = 1, Title = "Asus",
Colors = new List<Color> {
new Color { Id = 1, Name = "Blue"},
new Color { Id = 2, Name = "Orange"}
}
},
new product
{ Id = 2, Title = "Dell",
Colors = new List<Color> {
new Color { Id = 1, Name = "Yellow"},
new Color { Id = 2, Name = "Orange"},
new Color { Id = 3, Name = "Red"}
}
}
}
},
new Store{Id=2,Name="filo",City="san",
Products=new List<product>
{
new product{Id=3,Title="Asus",
Colors=new List<Color>{
new Color{Id=1,Name="Blue"},
new Color{Id=2,Name="Orange"}
}
},
new product{Id=4,Title="Dell",
Colors=new List<Color>{
new Color{Id=1,Name="Yellow"},
new Color{Id=2,Name="Lime"},
new Color{Id=3,Name="Red"}
}
}
}
}
};
I want to select all stores where Name ="Lilo" and products names is "Dell " and Color="Blue". I want do this in Entity Framework, not Linq.
I use this code but it doesn't work :
var test = Stores.Where(s => s.Name = "lilo" && s.Products.Where(p => p.Title == "Dell").FirstOrDefault().Title == "Dell" && s.Products.Where(c => c.Colors.Where(ct => ct.Name == "Blue").FirstOrDefault().Name = "Blue")).ToList();
How can I do this ?

Do this By Method Syntax :
var stlist = Stores.Where(s => s.Name.ToLower() == "lilo" && s.Products.Where(p => p.Colors.Any(c=>c.Name=="Blue") && p.Title == "Dell").FirstOrDefault().Title == "Dell").ToList();
Updated :
And Hopeless's Answers is (best answers):
var lslist2= Stores.Where(s => s.Name == "lilo" && s.Products.Any(p => p.Title == "Dell" && p.Colors.Any(c => c.Color.Name == "Blue"))).ToList();
And by Linq :
var test = (from s in Stores
from p in s.Products
from c in p.Colors
where s.Name=="Lilo" && p.Title=="Dell"&& c.Name=="Blue"
select s
).ToList();

Linq join 3 list <T>

I have three lists that I need to join together
class Person
{
public int PersonID{ get; set; }
public string FirstName{get; set;}
public string LastName {get; set;}
}
class Traffic
{
public DateTime Date{ get; set; }
public int PersonID;
public int TrafficID;
}
class TrafficType
{
public int TrafficID { get; set; }
public string Description { get; set; }
}
List<Person> Persons=GetPersons();
List<TrafficType> TrafficTypes=GetTrafficTypes();
List<Traffic> Traffics=GetTraffics();
I need an output like:
PersonID FirstName LastName Date Description
1001 David ... 2011/07/19 sample description

from person in Persons
from traffic in traffics
from trafficType in trafficTypes
where trafficType.TrafficID = traffic.TrafficID
where traffic.PersonID = person.PersonID
select new
{
PersonID = person.PersonID,
....
}

var result = Persons.Join(
Traffics,
person => person.PersonID,
trafic => trafic.PersonID,
(person, trafic) => new
{
PersonId = person.PersonID,
FirstName = person.FirstName,
LastName = person.LastName,
Date = trafic.Date,
TraficId = trafic.TrafficID
}).Join(
TrafficTypes,
a => a.TraficId,
traficType => traficType.TrafficID,
(a, traficType) => new
{
PersonId = a.PersonId,
FirstName = a.FirstName,
LastName = a.LastName,
Date = a.Date,
Description = traficType.Description
});

Here's a complete code sample with Linq query expression code that should get exactly what you're looking for:
using System;
using System.Collections.Generic;
using System.Linq;
class Person
{
public int Id { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
}
class Traffic
{
public DateTime Date { get; set; }
public int PersonId { get; set; }
public int TrafficId { get; set; }
}
class TrafficType
{
public int Id { get; set; }
public string Description { get; set; }
}
class Program
{
static void Main(string[] args)
{
var persons = new List<Person>()
{
new Person()
{
Id = 1001,
FirstName = "David",
LastName = "Jones",
},
};
var trafficTypes = new List<TrafficType>()
{
new TrafficType()
{
Id = 456,
Description = "sample description",
},
};
var traffics = new List<Traffic>()
{
new Traffic()
{
PersonId = 1001,
TrafficId = 456,
Date = DateTime.Now,
},
};
var joinedData = from p in persons
from t in traffics
from tt in trafficTypes
where p.Id == t.PersonId
&& tt.Id == t.TrafficId
select new
{
PersonId = p.Id,
FirstName = p.FirstName,
LastName = p.LastName,
// Remove time component, if present
Date = t.Date.Date,
Description = tt.Description,
};
foreach (var item in joinedData)
{
Console.WriteLine("{0}\t{1}\t{2}\t{3}\t{4}"
, item.PersonId
, item.FirstName
, item.LastName
, item.Date.ToShortDateString() // Don't print the time
, item.Description
);
}
}
}
The program output is:
1001 David Jones 7/19/2011 sample description

You can put them all in a class e.g. (Problem), then use a method for your output.
class Problem
{
public Problem()
{
}
public void Show()
{
// implement your output here
}
}
Or, if you are using Windows Forms app and interisting in Tables, you can use DataGridView control. For more information about it, visit http://msdn.microsoft.com/en-us/library/e0ywh3cz.aspx
Or, use DataGrid: http://www.codeproject.com/KB/grid/usingdatagrid.aspx