Access a var list<'a> from outside the method c#-CodePudding

I used LINQ to query two tables and showed the result in a var Spelers. This works fine but now I want to re-use this query outside the method after first clearing the var. I searched all resources known to me but couldn't find a solution.

The query Spelers uses the ObserverableCollections speler and golfclub. I try to create an app for my C# exam and I am c# novice. I hope someone can help me with this because I want all queries to be public accessible.

    public void JoinData()
    {
         var Spelers = (from spel in speler
                       join club in golfclub
                       on spel.ClubId equals club.Id
                       select new
                       {
                           Id = spel.Id,
                           Voornaam = spel.Voornaam,
                           Achternaam = spel.Achternaam,
                           Handicap = spel.Handicap,
                           Telefoon = spel.Telefoon,
                           Email = spel.Email,
                           Homeclub = club.Naam,
                           ClubId = spel.ClubId,
                           TeamId = spel.TeamId,
                           PuntenVoor = spel.PuntenVoor,
                           PuntenTegen = spel.PuntenTegen
                       }).ToList();

        if (Datagrid.ItemsSource == null)
        {
            Datagrid.ItemsSource = Spelers;
        }
    }

CodePudding user response：

I would strongly suggest separate type for such big set of various data.

For example:

public class MyDataCarrier
{
    public int Id { get; set; }
    public string Voornaam { get; set; }
    public string Achternaam { get; set; }
    public int Handicap { get; set; }
    public string Telefoon { get; set; }
    public string Email { get; set; }
    public string Homeclub { get; set; }
    public int ClubId { get; set; }
    public int TeamId { get; set; }
    public int PuntenVoor { get; set; }
    public int PuntenTege { get; set; }
}

And then just write the method:

public List<MyDataCarrier> GetData()
{
    return (
        from spel in speler
        join club in golfclub
        on spel.ClubId equals club.Id
        select new MyDataCarrier
        {
            // here you assing each property
        })
        .ToList();
}

And then you can easily reuse it wherever you want:

if (DataGrid.ItemsSource is null)
{
    DataGrid.DataSource = GetData();
}

CodePudding user response：

First of all, we should extract Speler as a property; we have to change anonymous type for something more suitable, let it be a named tuple (custom class is another possibility):

//TODO: Please, check types! Is "int Handicap" a correct guess?
public List<(
  int Id,
  string Voornaam,
  string Achternaam,
  int Handicap,
  string Telefoon,
  string Email,
  string Homeclub,
  int ClubId,
  int TeamId,
  int PuntenVoor,
  int PuntenTegen
)> Speler { get; private set; } = new ();

Then you can put

public void JoinData() {
  Spelers = (from spel in speler
             join club in golfclub
             on spel.ClubId equals club.Id
             select (spel.Id,
                     spel.Voornaam,
                     spel.Achternaam,
                     spel.Handicap,
                     spel.Telefoon,
                     spel.Email,
                     club.Naam,
                     spel.ClubId,
                     spel.TeamId,
                     spel.PuntenVoor,
                     spel.PuntenTegen))
           .ToList();

  if (Datagrid.ItemsSource == null)
    Datagrid.ItemsSource = Spelers;
}

CodePudding user response：

If you don't want your method to have a return value, you can have the value outside the method as well.

Var Spelers=new List<object>();
public void JoinData()
{
     Spelers = (from spel in speler
                   join club in golfclub
                   on spel.ClubId equals club.Id
                   select new
                   {
                       Id = spel.Id,
                       Voornaam = spel.Voornaam,
                       Achternaam = spel.Achternaam,
                       Handicap = spel.Handicap,
                       Telefoon = spel.Telefoon,
                       Email = spel.Email,
                       Homeclub = club.Naam,
                       ClubId = spel.ClubId,
                       TeamId = spel.TeamId,
                       PuntenVoor = spel.PuntenVoor,
                       PuntenTegen = spel.PuntenTegen
                   }).ToList();

    if (Datagrid.ItemsSource == null)
    {
        Datagrid.ItemsSource = Spelers;
    }
}