如何将两个ListBox的项目（代表数字）的值相加

Question

I'm trying to add two integers ( X and Y ) from different ListBoxes and show the total in a Label or TextBox.

I've tried copying the code from answered questions and emending to suit my code, but still struggling.

Dim lblTotal As Integer 
Dim X, Y As Integer 
Const WasGo = 35 
Const Vacuum = 20  

' The item description from the ListBox are supposed to be Constants
X = extBox.SelectItems(0) 
Y = intBox.SelectItems(0) 
lblTotal = X + Y

Answer 1

ListBox has a SelectedItems property. Assuming you have exactly one selected from each, this should work:

X = Convert.ToInt32(extBox.SelectedItems(0).ToString())
Y = Convert.ToInt32(intBox.SelectedItems(0).ToString())
lblTotal = X + Y

Few other tips/questions.

• I don't know what extBox, intBox, x and y are. Make sure your names are well defined.
• Checking against the index of an array is good (If extBox.SelectedItems.Length > 0 Then), but then you need a way to handle that condition. Maybe you need a prompt if nothing was selected
• What are you doing with an integer labeled lblTotal? Is this getting displayed somewhere?
• I'm assuming your listboxes both contain a list of integers.

Answer 2

You don't use those constants in this code. Convert the items to Integers so you can perform addition. To display in a label's text property call .ToString on the Integer

Private Sub OPCode()
    Dim lblTotal As Integer
    lblTotal = CInt(extBox.SelectItems(0)) + CInt(intBox.SelectItems(0))
    Label1.Text = lblTotal.ToString
End Sub