how to do calculations with multiple check boxes in vb.net? - vb.net

Question

for example i have 5 check boxes and these check boxes are names of products with different prices which are constant and displayed in five text boxes when a certain check box is checked
and i also have 5 text boxes for the quantity which depends on the input of the user. now for example i only checked 2 check boxes and input their quantity let say product one = 100 and product 2 = to 200 and i input 2 for both of their quantity display the total amount in only one text box. how can i code it because when i use the if else statement, it only calculate and display the price of one product while i have chosen or checked 2 products and when i used or in the if statement, when i only checked 2 check boxes and input their quantities, i get an error which is format string unhandle. This is my code:
If chkPopcorn.Checked = True Then
quantity1 = Integer.Parse(txtQuantityPopcorn.Text)
price1 = txtPricePopcorn.Text * quantity1
ElseIf chkBurger.Checked = True Then
quantity2 = Integer.Parse(txtQuantityBurger.Text)
price2 = txtPriceBurger.Text * quantity2
ElseIf chkSpaghetti.Checked = True Then
quantity3 = Integer.Parse(txtQuantitySpaghetti.Text)
price3 = txtPriceSpaghetti.Text * quantity3
ElseIf chkHotdog.Checked = True Then
quantity4 = Integer.Parse(txtQuantityHotdog.Text)
price4 = txtPriceHotdog.Text * quantity4
ElseIf chkCupcake.Checked = True Then
quantity5 = Integer.Parse(txtQuantityCupcake.Text)
price5 = txtPriceCupcake.Text * quantity5
End If
End If
txtSales.Text = price1 + price2 + price3 + price4 + price5

Answer 1

Simple to fix, use 5 If statements in a row, instead of ElseIf
If chkPopcorn.Checked = True Then
quantity1 = Integer.Parse(txtQuantityPopcorn.Text)
price1 = txtPricePopcorn.Text * quantity1
End If
If chkBurger.Checked = True Then
quantity2 = Integer.Parse(txtQuantityBurger.Text)
price2 = txtPriceBurger.Text * quantity2
End If
If chkSpaghetti.Checked = True Then
quantity3 = Integer.Parse(txtQuantitySpaghetti.Text)
price3 = txtPriceSpaghetti.Text * quantity3
End If
If chkHotdog.Checked = True Then
quantity4 = Integer.Parse(txtQuantityHotdog.Text)
price4 = txtPriceHotdog.Text * quantity4
End If
If chkCupcake.Checked = True Then
quantity5 = Integer.Parse(txtQuantityCupcake.Text)
price5 = txtPriceCupcake.Text * quantity5
End If
txtSales.Text = price1 + price2 + price3 + price4 + price5
End Sub