Creating a simple addition form application programmatically - vb.net

Question

I want to create a simple addition program in vb.net form application. Also i want to create all controls programmatically. I have three text boxes and one button. When the button is clicked , it take value from two text boxes and assign it to the third text box value.
I am unable to get text boxes string from button click handle.
My coding is as follows:
Public Class Form1
Public Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'Pushbutton
Dim PushButton As New Button()
PushButton.Text = "Add"
PushButton.Location = New Point(10, 100)
Me.Controls.Add(PushButton)
AddHandler PushButton.Click, AddressOf myButtonHandler_Click
'
'TextBox1
Dim TextBox1 As New TextBox
TextBox1.Location = New Point(10, 3)
Me.Controls.Add(TextBox1)
'TextBox2
Dim TextBox2 As New TextBox
TextBox2.Location = New Point(200, 3)
Me.Controls.Add(TextBox2)
Dim TextBox3 As New TextBox
TextBox3.Location = New Point(200, 100)
Me.Controls.Add(TextBox3)
End Sub
Private Sub myButtonHandler_Click(ByVal sender As Object, ByVal e As EventArgs)
End Sub
Public Function ADD(x As Double, y As Double) As Double
ADD = x + y
End Function
End Class

Answer 1

Moving the declaration of the controls to Form level allows them to be seen in all the methods of the form.
Public Class Form3
Private TextBox1 As New TextBox
Private TextBox2 As New TextBox
Private TextBox3 As New TextBox
Private PushButton As New Button
Private Sub Form3_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'Pushbutton
PushButton.Text = "Add"
PushButton.Location = New Point(10, 100)
Me.Controls.Add(PushButton)
AddHandler PushButton.Click, AddressOf myButtonHandler_Click
'TextBox1
TextBox1.Location = New Point(10, 3)
Controls.Add(TextBox1)
'TextBox2
TextBox2.Location = New Point(200, 3)
Controls.Add(TextBox2)
'TextBox3
TextBox3.Location = New Point(200, 100)
Controls.Add(TextBox3)
End Sub
Private Sub myButtonHandler_Click(ByVal sender As Object, ByVal e As EventArgs)
Dim firstNumber = CDbl(TextBox1.Text)
Dim secondNumber = CDbl(TextBox2.Text)
TextBox3.Text = ADD(firstNumber, secondNumber).ToString
End Sub
Public Function ADD(x As Double, y As Double) As Double
ADD = x + y
End Function
End Class

Answer 2

You can technically do it the way you were, but only if you use an anonymous event handler for the button click event as shown below:
Public Class Form1
Public Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'TextBox1
Dim TextBox1 As New TextBox
TextBox1.Location = New Point(10, 3)
Me.Controls.Add(TextBox1)
'TextBox2
Dim TextBox2 As New TextBox
TextBox2.Location = New Point(200, 3)
Me.Controls.Add(TextBox2)
Dim TextBox3 As New TextBox
TextBox3.Location = New Point(200, 100)
Me.Controls.Add(TextBox3)
'Pushbutton
Dim PushButton As New Button()
PushButton.Text = "Add"
PushButton.Location = New Point(10, 100)
Me.Controls.Add(PushButton)
AddHandler PushButton.Click, Sub()
Dim dblA, dblB As Double
If Double.TryParse(TextBox1.Text, dblA) AndAlso Double.TryParse(TextBox2.Text, dblB) Then
TextBox3.Text = ADD(dblA, dblB)
Else
MessageBox.Show("One or more Invalid Inputs")
End If
End Sub
End Sub
Public Function ADD(x As Double, y As Double) As Double
ADD = x + y
End Function
End Class
Though I do recommend moving those control declarations out to Form level as Mary suggested.