I have a following object structure
a Group has Many Teams and a Team has many Players
m_Groups is an observable collection of groups
I'm trying to get the Team name given a group name and a players name I can do this like in for each, but having trouble converting it to LINQ:
Dim retVal As String = String.empty
For Each g In m_Groups
For Each t In g.Teams
For Each p In t.Players
If p.PlayerName.Equals(name) Then
retVal = t.TeamName
End If
Next
Next
Next
Dim teamName = (From group in Groups _
From team In group.Teams _
From player In team.Players _
Where player.PlayerName.Equals(name) _
Select team.TeamName).FirstOrDefault()
(Disclaimer: I'm mostly guessing the VB syntax above.)
Also, my actual way of dealing with situations like youre would be to give players a Team property and connect them up once after loading instead of doing a lookup every time. (Assuming the player assignments don't change, a bidirectional connection would require some boilerplate to maintain.)
There are obviously several ways of doing it, here is what came to my mind
var team = m_Groups
.SelectMany(g=>g.Teams)
.FirstOrDefault(t=>t.Players.Any(p=>p.PlayerName == name));
I hope you'll be able to convert it to VB yourself
With your setup, I am assuming you would perform a LINQ query every time you need to search for a particular team. A better approach would be to have a linear structure, such as a dictionary, which has name as a key.
Keeping close to what you got there, here is some code to play with:
Option Strict On
Public Class Form1
Class MyGroup
Public Teams As New List(Of MyTeam)
End Class
Class MyTeam
Public Players As New List(Of MyPlayer)
Public TeamName As String
End Class
Class MyPlayer
Public PlayerName As String
End Class
Dim m_Groups As New List(Of MyGroup)
Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
Dim p As New MyPlayer With {.PlayerName = "Player"}
Dim t As New MyTeam With {.TeamName = "Team", .Players = New List(Of MyPlayer)({p})}
m_Groups.Add(New MyGroup With {.Teams = New List(Of MyTeam)({t})})
Dim name As String = "Player" 'player name to be searched
Dim teamName = (From group In m_Groups _
From team In group.Teams _
From player In team.Players _
Where player.PlayerName.Equals(name) _
Select team.TeamName).FirstOrDefault()
End Sub
End Class
It was heavily influenced by @millimoose's answer, with two slight changes:
Dim team -> Dim teamName, you cannot have two team variables in the same scope.Select player became Select team.TeamName.