value cannot be null parameter name: item[Answered] RSS

• • Reply
  grantify

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  value cannot be null parameter name: item

  May 09, 2013 07:31 AM|grantify|LINK

  ok so I want my program to avoid from crashing if the 'user' didn't check a certain thing, so I want to be able to click the add button without it crashing on me because you cannot select 'null'

  Private Sub btnAdd_Click(sender As System.Object, e As System.EventArgs) Handles btnAdd.Click

  
  'clear out grand total variable

  'so if user changes mind it does not contain
  'old values
  total = 0
  'as long as the variable contains something!
  If Pizza <> "" Then

  End If
  ' add up the decimal variables
  'for a grand total price
  total = total + PizzaPrice
  total = total + Pizzas(0)
  total = total + Pizzas(1)
  total = total + Pizzas(2)
  total = total + Pizzas(3)
  total = total + Pizzas(4)
  'clear the list box
  'in case user changes
  'items selected
  TotalPrice.Items.Clear()
  ' add title
  TotalPrice.Items.Add("Pizza Selected:--")
  TotalPrice.Items.Add(Pizza)

  For i As Integer = 0 To 4

  Next
  If Not Pizzas(i) = "" Then

  TotalPrice.Items.Add(Pizzas(i))
  End If

  If TwoSizes <> "" Then

  End If

  total = total + SizesPrice
  total = total + SizesTotalPrice(0)
  total = total + SizesTotalPrice(1)
  TotalPrice.Items.Add("Size Selected:--")
  TotalPrice.Items.Add(TwoSizes)

  For i As Integer = 0 To 1

  
  If Not SizesTotalPrice(i) = "" Then
  TotalPrice.Items.Add(SizesTotalPrice(i))

  End If

  
  Next

  If base <> "" Then

  
  total = total + baseprice
  total = total + twobases(0)
  total = total + twobases(1)
  TotalPrice.Items.Add("Base Selected:--")
  TotalPrice.Items.Add(base)
  For i As Integer = 0 To 1

  If Not twobases(i) = "" Then
  TotalPrice.Items.Add(twobases(i))
  End If
  Next

  total = total + drinkprice
  total = total + twodrinks(0)
  total = total + twodrinks(1)
  total = total + twodrinks(2)
  TotalPrice.Items.Add("Drink Selected:--")
  TotalPrice.Items.Add(drink)
  For i As Integer = 0 To 2

  If Not twodrinks(i) = "" Then
  TotalPrice.Items.Add(twodrinks(i))

  End If
  Next

  total = total + toppingprice
  total = total + toppingprice1
  total = total + toppingprice2
  total = total + toppingprice3
  total = total + toppings(0)
  total = total + toppings(1)
  total = total + toppings(2)
  total = total + toppings(3)
  TotalPrice.Items.Add("Topping Selected:--")
  TotalPrice.Items.Add(topping)
  TotalPrice.Items.Add(topping1)
  TotalPrice.Items.Add(topping2)
  TotalPrice.Items.Add(topping3)

  For i As Integer = 0 To 3

  If Not toppings(i) = "" Then
  TotalPrice.Items.Add(toppings(i))
  End If
  Next

  'add a dotted line
  TotalPrice.Items.Add("----------")
  'etc etc
  TotalPrice.Items.Add("Total £" & total)

  End If

  End Sub

• • Reply
  smirnov

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  9075 Posts

  Re: value cannot be null parameter name: item

  May 09, 2013 01:30 PM|smirnov|LINK

  Where do you get your error and how exactly its message looks like? There is no reference to "item" as mentioned in the title of your post.

  The code is somehow strange and incomplete. For example, 

  If Pizza <> "" Then
  ------------what should happen here?
  End If
  ...
  TotalPrice.Items.Add(Pizza) ------ why you add an empty Pizza (if Pizza = "")

  then

  For i As Integer = 0 To 4
  -------- what this enumeration is for?
  Next

  and so on...