List of lists of each row from SQL database using Entity Framework & C#

Question

I have database and I'm using Entity Framework to create models (database first). I want to loop somehow through my model so that I can create a list of each row. Then I want to create list of those lists. Also lists have to be lists of objects not strings.

Model class:

public class person
{
    public int ID {get; set;}
    public string Code {get; set;}
    public int Time {get; set;}
    public string Name {get; set;}
}

Now I have such a person in the database and I want to create a list that contains ID, Code, Time and Name taken from one row. And then I want to create a list of those Person lists. I assume that I should use foreach or for loop but I don't know how should I start.

Edit: I have database that looks like this:

ID | Code | Time | Name
 1    200    10    Paul
 2    201    20    Tom
 3    203    25    Jacob
 4    208    10    Agnes

Now i want to create a list with one row. That list should look like:

List<1,200,10,Paul>

Then i want to create or rather add to list of lists each list created from those rows. So that i would have list that contains lists of Persons.

Your question is unclear. If you want a list of people your can get that with something like context.Persons.ToList(); This will return a List<Person>. You would use foreach in your view to loop through that list. — Steve Greene
– Steve Greene, Commented Sep 18, 2017 at 22:25
I need that list of lists in controller to do other things with it. — Pawli
– Pawli, Commented Sep 19, 2017 at 15:27
Still not sure what "list of lists" means. You have only shown a person model with no relationships so all you can really get is a List<Person>. It seems to me you are using MVC. So in your controller GET you would fill a list of persons from the context as shown. Then you would pass and display this in a View with foreach. More info needed... — Steve Greene
– Steve Greene, Commented Sep 19, 2017 at 16:33
I don't need to pass it to view. I want to create List<List<Person>>. — Pawli
– Pawli, Commented Sep 19, 2017 at 16:46
Your question is very unclear. If you have List<List<Person>>, what is inside each List<Person> that separates it from the others? — NetMage
– NetMage, Commented Sep 19, 2017 at 17:45

NetMage · Accepted Answer · 2017-09-18 23:13:27Z

1

I can think of no legitimate reason to do this, but perhaps this is what you mean?

var listOfLists = db.Persons.Select(p => new List<object> {
    (object)p.ID,
    (object)p.Code,
    (object)p.Time,
    (object)p.Name
}).ToList();

answered Sep 18, 2017 at 23:13

NetMage

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2 Comments

Pawli Over a year ago

But what does it create? List of all ids, list of all Codes etc?

NetMage Over a year ago

This creates a List<object> from each row, and then creates a List<List<object>> from those, which is what your question states. If that isn't what is desired, I would improve your question, including adding examples.

V Zabavnov · Accepted Answer · 2017-09-19 02:04:18Z

0

If you want to just go through list of Person's data item you need just foreach:

foreach(var data in ctx.Persons.Select( p => new {p.ID, p.Code, p.Time, p. Name})){
    // here you have data object with 4 items
}

answered Sep 19, 2017 at 2:04

V Zabavnov

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2 Comments

Pawli Over a year ago

Unfortunately i don't want anonymous types. Can i specify types of these 4 objects?

NetMage Over a year ago

The four objects have types. You can specify a class instead of having an anonymous object, but then you are back to just using List<Person>.

Steve Greene · Accepted Answer · 2017-09-19 18:07:25Z

Here is one way to create a <List<List<Person>>:

[HttpGet]
public ActionResult PersonIndex()
{
    List<List<Person>> personLists = new List<List<Person>>();
    var personsCodeA = context.Persons.Where(p => p.Code == "A").ToList();
    var personsCodeB = context.Persons.Where(p => p.Code == "B").ToList();
    var personsCodeX = context.Persons.Where(p => p.Code == "X").ToList();
    personLists.Add(personsCodeA);
    personLists.Add(personsCodeB);
    personLists.Add(personsCodeX);
    return View(personLists);
}

Now in the view (or where ever) you could do:

foreach (var currentList in personLists)
{
    // process each list
    console.writeline(string.Format("People in code {0}:",currentList[0].Code));  //todo null check
    foreach (var person in currentList])
    {
        // process each person in the current list
        console.writeline(string.Format("  Person: {0}",person.Name));  //todo null check
        var personID = person.ID;
        var personCode = person.Code;
        var personName = person.Name;
        var personTime = person.Time;
    }
}

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