Giving Dynamically Created Shapes a Name - vb.net

Question

I'm designing a hexagon grid and I need to be able to name each hexagon, so I can refer to them later. Below is my class, it generates the hexagon grid, and I've labeled the code throughout so you can understand what's happening.
I've been searching for a while now reading a lot about Graphics, but I can't get a working design with the answers I've seen offered. Perhaps, I'm going about this wrong by using Graphics, but my plan is to be able to click on each hexagon and do something with it.
Note: If you see a way to improve my code let me know. It's appreciated!
' Generate Hexagon Grid
Private Sub Form1_Paint(sender As Object, e As PaintEventArgs) Handles Me.Paint
' Hexagon Grid Parameters
Dim HexagonRadius As Integer = 20 ' Fix "Position Hexagon Grid Columns" Before Changing Hexagon Radius
Dim GridSize As Integer = 10
' Generate Hexagon Grid
Dim HexagonX As Integer = HexagonRadius
Dim HexagonY As Integer = HexagonRadius
For i As Integer = 1 To GridSize
For j As Integer = 1 To GridSize
' Hexagon Vertex Coordinates
Dim point1 As New Point((HexagonX - HexagonRadius), (HexagonY))
Dim point2 As New Point((HexagonX - (HexagonRadius / 2)), (HexagonY + ((HexagonRadius / 2) * Math.Sqrt(3))))
Dim point3 As New Point((HexagonX + (HexagonRadius / 2)), (HexagonY + ((HexagonRadius / 2) * Math.Sqrt(3))))
Dim point4 As New Point((HexagonX + HexagonRadius), (HexagonY))
Dim point5 As New Point((HexagonX + (HexagonRadius / 2)), (HexagonY - ((HexagonRadius / 2) * Math.Sqrt(3))))
Dim point6 As New Point((HexagonX - (HexagonRadius / 2)), (HexagonY - ((HexagonRadius / 2) * Math.Sqrt(3))))
Dim hexagonPoints As Point() = {point1, point2, point3, point4, point5, point6}
' Create Hexagon
e.Graphics.FillPolygon(Brushes.Green, hexagonPoints)
' Hexagon Outline
e.Graphics.DrawLine(Pens.Black, point1, point2)
e.Graphics.DrawLine(Pens.Black, point2, point3)
e.Graphics.DrawLine(Pens.Black, point3, point4)
e.Graphics.DrawLine(Pens.Black, point4, point5)
e.Graphics.DrawLine(Pens.Black, point5, point6)
e.Graphics.DrawLine(Pens.Black, point6, point1)
' Position Hexagon Grid Columns
HexagonY += 34 ' Specific to Hexagon Radius: 20
Next
If i Mod 2 > 0 Then
HexagonY = 36.75 ' Specific to Hexagon Radius: 20
Else
HexagonY = 20 ' Specific to Hexagon Radius: 20
End If
HexagonX += 30 ' Specific to Hexagon Radius: 20
Next
End Sub

Answer 1

You'll need to create some Hexagon class with it's coordinates and (maybe name, if really needed). And save them to some suitable collection (2-dimensional array maybe?)
This should happen somewhere outside your Paint event and might be recalculated on grid SizeChanged event.
Inside your Paint event you'll just iterate throught existing collection and render according to pre-computed coordinates.
OnClick event will loop throught the same collection to find specific Hexagon for updating (changing background color for example) and forcing form to repaint to take effect.
For large rendering you should consider rendering to bitmap first and drawing that final bitmap to e.Graphics for faster work. Your bitmap could be cached as well to speed up even more.
EDIT: Code sample added
Turn Option Strict On in your project properties to avoid many problems in your code that you're not aware of.
Public Class frmTest
Private Const HexagonRadius As Integer = 20
Private Const GridSize As Integer = 10
Private fHexagons As New List(Of Hexagon)
Private fCache As Bitmap
Private fGraphics As Graphics
Private Sub ResetHexagons() 'Call when some parameter changes (Radius/GridSize)
fHexagons.Clear()
Invalidate()
End Sub
Private Function EnsureHexagons() As List(Of Hexagon)
Dim X, Y As Single, xi, yi As Integer
If fHexagons.Count = 0 Then
X = HexagonRadius : Y = HexagonRadius
For xi = 1 To GridSize
For yi = 1 To GridSize
fHexagons.Add(New Hexagon(HexagonRadius, X, Y))
Y += 34
Next
'Do your math to get theese values from HexagonRadius value
If xi Mod 2 > 0 Then
Y = 36.75
Else
Y = 20
End If
X += 30
Next
fCache?.Dispose()
fGraphics?.Dispose()
fCache = New Bitmap(GridSize * HexagonRadius * 2, GridSize * HexagonRadius * 2)
fGraphics = Graphics.FromImage(fCache)
For Each H As Hexagon In fHexagons
H.Render(fGraphics)
Next
End If
Return fHexagons
End Function
Private Sub frmTest_Paint(sender As Object, e As PaintEventArgs) Handles Me.Paint
EnsureHexagons()
e.Graphics.DrawImageUnscaled(fCache, Point.Empty)
End Sub
Private Sub frmTest_MouseClick(sender As Object, e As MouseEventArgs) Handles Me.MouseClick
Dim H As Hexagon = EnsureHexagons.FirstOrDefault(Function(X) X.Contains(e.Location))
If H IsNot Nothing Then
H.Checked = Not H.Checked
H.Render(fGraphics) 'Update cache without repainting all
Invalidate()
End If
End Sub
End Class
Public Class Hexagon
Public ReadOnly Radius, X, Y As Single
Public ReadOnly Points() As PointF
Public Property Checked As Boolean
Public Sub New(Radius As Single, X As Single, Y As Single)
Me.Radius = Radius : Me.X = X : Me.Y = Y
Points = {New PointF((X - Radius), (Y)),
New PointF((X - (Radius / 2)), CSng(Y + ((Radius / 2) * Math.Sqrt(3)))),
New PointF((X + (Radius / 2)), CSng(Y + ((Radius / 2) * Math.Sqrt(3)))),
New PointF((X + Radius), (Y)),
New PointF((X + (Radius / 2)), CSng(Y - ((Radius / 2) * Math.Sqrt(3)))),
New PointF((X - (Radius / 2)), CSng(Y - ((Radius / 2) * Math.Sqrt(3.0!))))}
End Sub
Public Sub Render(G As Graphics)
' Create Hexagon
G.FillPolygon(If(Checked, Brushes.Blue, Brushes.Green), Points)
' Hexagon Outline
For i As Integer = 0 To Points.Length - 1
G.DrawLine(Pens.Black, Points(i), Points((i + 1) Mod Points.Length))
Next
End Sub
Public Function Contains(P As Point) As Boolean
'Do your math here, this is just simplified estimation
Return X - Radius <= P.X AndAlso P.X <= X + Radius AndAlso Y - Radius <= P.Y AndAlso P.Y <= Y + Radius
End Function
End Class