How to draw points when user clicks on a map - vb.net

Question

Dim HaveToDraw As New Boolean
Dim xMouse As Integer
Dim yMouse As Integer
Private Sub foo(sender As Object, e As PaintEventArgs) Handles PictureBox1.Paint
If HaveToDraw = True Then
e.Graphics.FillEllipse(Brushes.Green, xMouse, yMouse, 10, 10)
End If
HaveToDraw = False
End Sub
Sub PictureBox1_MouseClick(sender As Object, e As MouseEventArgs) Handles PictureBox1.MouseClick
If RadioButton1.Checked = True Then
xMouse = e.X
yMouse = e.Y
HaveToDraw = True
PictureBox1.Refresh()
End If
End Sub
This code lets the user draw an elipse when he clicks on any point on the map, but there are 2 problems with it: 1 - The user is able to draw only one elipse; 2 - The user is not able to erase a previously created elipse.
So, how can I do that solving these two problems?

Answer 1

As #Idle_Mind suggested, you could use a list to store your points, and a right-click event to remove the points:
Dim radius as Integer = 5
Private points As New List(Of Point)()
Private Sub pictureBox1_MouseClick(sender As Object, e As MouseEventArgs)
If e.Button = System.Windows.Forms.MouseButtons.Left Then
points.Add(e.Location) ' add point on left click
ElseIf e.Button = System.Windows.Forms.MouseButtons.Right Then
For i As Integer = 0 To points.Count - 1 ' remove points on right-click
If distance(points(i).X, points(i).Y, e.Location) < radius Then
points.RemoveAt(i)
End If
Next
End If
pictureBox1.Refresh()
End Sub
'helper function
Private Function distance(x__1 As Integer, y__2 As Integer, mousep As Point) As Integer
Dim X__3 As Integer = CInt(Math.Pow(CDbl(x__1 - mousep.X), 2))
Dim Y__4 As Integer = CInt(Math.Pow(CDbl(y__2 - mousep.Y), 2))
Return CInt(Math.Sqrt(CDbl(X__3 + Y__4)))
End Function
Private Sub pictureBox1_Paint(sender As Object, e As PaintEventArgs)
For i As Integer = 0 To points.Count - 1
e.Graphics.FillEllipse(Brushes.Green, points(i).X - radius, points(i).Y - radius, radius * 2, radius * 2)
Next
End Sub
I also changed the paint code to draw the circles so that they are centered under the mouse-click.