The input String is not in correct format even though my variable is an integer - vb.net

Question

Private Sub shirtnum_KeyPress(sender As Object, e As KeyPressEventArgs) Handles shirtnum.KeyPress ("this is suppose to type in any number using into the textbox using your keyboard")
Dim Ch As Char = e.KeyChar
If Not Char.IsDigit(Ch) AndAlso Asc(Ch) <> 8 Then
e.Handled = True
End If
End Sub
Private Sub addshbtn_Click(sender As Object, e As EventArgs) Handles addshbtn.Click
Dim t As Integer = Integer.Parse(shirtnum.Text) ("this is to add 1 number to the textbox")
t += 1
shirtnum.Text = t
addshbtn.Enabled = True
pricetxt_TextChanged(sender, e)
End Sub
Private Sub minusshbtn_Click(sender As Object, e As EventArgs) Handles minusshbtn.Click ("this is to minus 1 number from the textbox")
Dim t As Integer = Integer.Parse(shirtnum.Text)
t += -1
If t <= 0 Then
t = 0
End If
shirtnum.Text = t
pricetxt_TextChanged(sender, e)
End Sub
Private Sub shirtnum_TextChanged(sender As Object, e As EventArgs) Handles shirtnum.TextChanged
End Sub
Private Sub pricetxt_TextChanged(sender As Object, e As EventArgs) Handles pricetxt.TextChanged
"Dim t As Integer = Integer.Parse(shirtnum.Text) -- this is where the error appears **NOTE** this this code works without this sub"
t = 1.0
pricetxt.Text = ("$" & t * 15 & ".00")
pricetxt.BorderStyle = 0
pricetxt.BackColor = Me.BackColor
End Sub
Got an issue with my assignment is that the code appears to say that the input string is not in the correct format, even though my integer is a number.
If someone can help me out with this, this would be a big help, thanks!