Join and add a group to LINQ

Question

These are my input tables:

Persons Table:
================
ID  Code
------------------------
1   Person1     # Person1: John Smith, 25, 50Kg
2   Person2     # Person2: William Brown, 30, 80Kg
3   Person3     # Person3: James Miller, 32, 73Kg

StringProperties Table:
=========================
ID  PersonID    Name        Value
----------------------------------------------
1   1           FirstName   John        # Person1: John Smith, 25, 50Kg
2   1           LastName    Smith       # Person1: John Smith, 25, 50Kg
3   2           FirstName   William     # Person2: William Brown, 30, 80Kg
4   2           LastName    Brown       # Person2: William Brown, 30, 80Kg
5   3           FirstName   James       # Person3: James Miller, 32, 73Kg
6   3           LastName    Miller      # Person3: James Miller, 32, 73Kg

NumericProperties Table:
=========================
ID  PersonID    Name    Value
-----------------------------------------
1   1           Age     25          # Person1: John Smith, 25, 50Kg
2   1           Weight  50          # Person1: John Smith, 25, 50Kg
3   2           Age     30          # Person2: William Brown, 30, 80Kg
4   2           Weight  80          # Person2: William Brown, 30, 80Kg
5   3           Age     32          # Person3: James Miller, 32, 73Kg
6   3           Weight  73          # Person3: James Miller, 32, 73Kg

I want to write a LINQ query that generates the following result:

Result:
==========
Code        FirstName   LastName    Age     Weight
-----------------------------------------------------------------
Person1     John        Smith       25      50
Person2     William     Brown       30      80
Person3     James       Miller      32      73

This is my code, but it does not work correctly:

var q = from p in db.Persons
        join s in db.StringProperties on p.ID equals s.PersonID
        join n in db.NumericProperties on p.ID equals n.PersonID
        group p by p.Code into g
        select new
        {
            g.Key,
            g
        };

Answer 1

Assuming we have objects that look something like this:

public class Person
{
    public int ID { get; set; }
    public string Code { get; set; }
}

public class StringProperty
{
    public int ID { get; set; }
    public int PersonID { get; set; }
    public string Name { get; set; }
    public string Value { get; set; }
}

public class NumericProperty
{
    public int ID { get; set; }
    public int PersonID { get; set; }
    public string Name { get; set; }
    public int Value { get; set; }
}

And data like this:

var persons = new List<Person> 
{
    new Person { ID = 1, Code = "Person1" },
    new Person { ID = 2, Code = "Person2" },
    new Person { ID = 3, Code = "Person3" }
};

var stringProperties = new List<StringProperty>
{
    new StringProperty { ID = 1, PersonID = 1, Name = "FirstName", Value = "John" },
    new StringProperty { ID = 2, PersonID = 1, Name = "LastName", Value = "Smith" },
    new StringProperty { ID = 3, PersonID = 2, Name = "FirstName", Value = "William" },
    new StringProperty { ID = 4, PersonID = 2, Name = "LastName", Value = "Brown" },
    new StringProperty { ID = 5, PersonID = 3, Name = "FirstName", Value = "James" },
    new StringProperty { ID = 6, PersonID = 3, Name = "LastName", Value = "Miller" }
};

var numericProperties = new List<NumericProperty>
{
    new NumericProperty { ID = 1, PersonID = 1, Name = "Age", Value = 25 },
    new NumericProperty { ID = 2, PersonID = 1, Name = "Weight", Value = 50 },
    new NumericProperty { ID = 3, PersonID = 2, Name = "Age", Value = 30 },
    new NumericProperty { ID = 4, PersonID = 2, Name = "Weight", Value = 80 },
    new NumericProperty { ID = 5, PersonID = 3, Name = "Age", Value = 32 },
    new NumericProperty { ID = 6, PersonID = 3, Name = "Weight", Value = 73 }
};

We can attach people to a table of row values ​​like this, and at the same time collapse it:

var stringValues = from p in persons
                   join s in stringProperties on p.ID equals s.PersonID
                   group s by p.Code into g 
                   select new
                   {
                       Code = g.Key,
                       FirstName = g.Where(s => s.Name == "FirstName").First().Value,
                       LastName = g.Where(s => s.Name == "LastName").First().Value,
                   };

Do the same for numerical values:

var numericValues = from p in persons
                    join n in numericProperties on p.ID equals n.PersonID
                    group n by p.Code into g 
                    select new
                    {
                        Code = g.Key,
                        Age = g.Where(n => n.Name == "Age").First().Value,
                        Weight = g.Where(n => n.Name == "Weight").First().Value,
                    };

Now connect them together:

var q = from s in stringValues
        join n in numericValues on s.Code equals n.Code
        select new 
        {
            Code = s.Code,
            FirstName = s.FirstName,
            LastName = s.LastName,
            Age = n.Age,
            Weight = n.Weight
        };

You can do this in one statement, but it is easier if you separate it as follows.

In fact, I would rather do this in a stored procedure, since it is faster there.

Answer 2

. .

-, DavidG .

1:

var query =
    from p in persons
    join s in stringProperties on p.ID equals s.PersonID into gss
    join n in numericProperties on p.ID equals n.PersonID into gns
    from fn in gss.Where(x => x.Name == "FirstName")
    from ln in gss.Where(x => x.Name == "LastName")
    from a in gns.Where(x => x.Name == "Age")
    from w in gns.Where(x => x.Name == "Weight")
    select new
    {
        p.Code,
        FirstName = fn.Value,
        LastName = ln.Value,
        Age = a.Value,
        Weight = w.Value,
    };

2:

var query =
    from p in persons
    join s in stringProperties on p.ID equals s.PersonID into gss
    join n in numericProperties on p.ID equals n.PersonID into gns
    let sl = gss.ToLookup(x => x.Name, x => x.Value)
    let nl = gns.ToLookup(x => x.Name, x => x.Value)
    from FirstName in sl["FirstName"]
    from LastName in sl["LastName"]
    from Age in nl["Age"]
    from Weight in nl["Weight"]
    select new
    {
        p.Code,
        FirstName,
        LastName,
        Age,
        Weight,
    };

: