VB.Net 2010 "Object reference not set to an instance of an object." when declaring a variable from a Dictionary with a list as the value - vb.net

Question

This is a school project for Programming (not an assessment or assignment, so I'm not cheating) where I have to make a 7-segment displaySource 1. I decided instead of going the traditional way and manually setting each RectangeShape to visible on each button pressed to display a number; store the corresponding number and which RectangleShape(s) to turn on as a key-value pair in a dictionary. I have some knowledge of Python, so this is where I got the idea from. My formSource 2 has 7 RectangleShape(s) and 10 Button(s). Just as an experiment since it's my first time working with Dictionaries and Lists in VB.net, I decided to only try it out for the number 1 for now (shp4 and shp5 should be visible). Here is the dictionary I made:
Dim Numbers As New Dictionary(Of Integer, List(Of PowerPacks.Shape)) From {{1, New List(Of PowerPacks.Shape) From {shp4, shp5}}, {2, New List(Of PowerPacks.Shape) From {shp2, shp3}}}
Here is the code for the button (btn1):
Private Sub btn1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btn1.Click
Dim Thing As PowerPacks.Shape = Numbers(1)(0)
Thing.Visible = True
End Sub
When the program gets to the line that says Thing.Visible = True, it throws an error. It's a NullReferenceException that states Object reference not set to an instance of an object. Any ideas on how to fix this?
Sources
Source 1:
Source 2:

Answer 1

Programming is not magic. It works pretty much as you'd expect. If you are getting Nothing out of your List within a Dictionary then you must be putting Nothing in. Did you use the debugger before posting? Did you actually look at the value of shp2, etc, when this line is executed:
Dim Numbers As New Dictionary(Of Integer, List(Of PowerPacks.Shape)) From {{1, New List(Of PowerPacks.Shape) From {shp4, shp5}}, {2, New List(Of PowerPacks.Shape) From {shp2, shp3}}}
Based on your use of that Numbers variable in the second code snippet, it must be a member variable, which means that that first code snippet is outside any method, which means that it is executed before the class constructor, which means that no controls have been created at that time, which means that any fields that refer to controls can't be anything but Nothing. If you had put a breakpoint on that line and used the debugger, as you should have, then you'd have seen that.
The solution is not actually add the Shapes to the collection until they are created. That means after the call to InitializeComponent. That means that you can create your own constructor and do it there if you want, but that you should probably just do it in the Load event handler. Just declare the Dictionary variable without creating an object:
Private numbers As Dictionary(Of Integer, PowerPacks.Shape())
Note that I have provide an explicit access modifier, which you should ALWAYS do for all members, and also started the name with a lower-case letter, which you probably ought to do for all private fields. You then create the object in the load event handler:
numbers As New Dictionary(Of Integer, PowerPacks.Shape()) From {{1, {shp4, shp5}},
{2, {shp2, shp3}}}
I've taken the liberty of simplifying that by using arrays rather than Lists that add no value.

Answer 2

On your 7-Segment Display Form, I would use a List (of String) containing which rectangles are turned on for each dictionary key (number). This would require first programatically adding the 7 shapes onto the form (looks like you already coded that), and then in each button (for numbers) just pick off which rectangles are turned on and change their background color. "Front loading" all the Shapes (rectangles) into the Dictionary is probably unnecessary, since they are already manually fixed on the Form. If they are not, then pull out the code that places them on the form and run that first, one time, when the form loads. Using this approach, you don't have to worry about Shapes any more.
In Form 1, add:
Dim dicRSBackColor As New Dictionary(Of Integer, List(Of String))
Dim SC As New ShapeContainer
In Form1_Load, add the following:
'define each of the 7 rectangles using, e.g.:
Dim myrec4 As New RectangleShape
myrec4.Name = "shp4"
myrec4.Visible = True
myrec4.BringToFront()
'add locations and size to myrec4
myrec4.Top=100
myrec4.Left=100
myrec4.Width=10
myrec4.Height=100
'then add myrec4 to Shape container
SC.Shapes.Add(myrec4)
'add myrec4 to Form1
Me.Controls.Add(myrec4)
'do the above for all 7 rectangleshapes
'For the dictionary, add number 1's rectangleshape (turned on)
Dim mylist As List(Of String)
mylist.Add("shp4")
mylist.Add("shp5")
dicRSBackColor.Add(1, mylist)
'add number 2 rectangles (turned on)
mylist.Clear()
mylist.Add("shp1")
mylist.Add("shp3")
mylist.Add("shp4")
mylist.Add("shp6")
mylist.Add("shp7")
dicRSBackColor.Add(2, mylist)
'continue until all 7 rec's added
Last, in the button _Click for number 1, use the following:
'First change background color of all rectangleshapes to Form1's back color
For Each rs As RectangleShape In Me.SC.Shapes
rs.BackColor = Me.BackColor
Next
'Now pull the list of shapes that are turned on for number 1 using the dictionary
Dim mylist1 As List(Of String)
mylist1 = dicRSBackColor(1) 'you're pulling the value for key=1, which is a list of strings
'use a double loop and find out when the list value is the same as the name of the rectangleshape, and then set the back color to orange
For Each item In mylist1
For Each rs As RectangleShape In Me.SC.Shapes
If item = rs.Name Then rs.BackColor = Color.Orange
Next
Next