Графический редактор - рисование линий и фигур - Visual Basic .NET

Public Class Form1
    
    Private Sub Form1_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseMove
 
        Label7.Text = Str(e.X) & Str(e.Y)
    End Sub
 
    Dim a, b As Integer
   
    Dim i As Boolean
    Dim xl As Integer
    Dim yl As Integer
    Dim x2 As Integer
    Dim y2 As Integer
 
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        a = 1
    End Sub
 
    Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
        a = 2
    End Sub
 
    Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
        a = 3
    End Sub
 
    Private Sub PictureBox1_Click(sender As Object, e As EventArgs) Handles PictureBox1.Click
 
    End Sub
 
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        If a = 1 Then
            MsgBox(a)
        End If
    End Sub
End Class