Hi all, I wrote this sample code :
Private Sub Button1_Click( ..... ) Handles Button1.Click
Dim x As New ArrayList
x.Add(1)
x.Add(1)
TestArrayList(x )
MsgBox("TestArr ayList : " & x.Count.ToStrin g)
End Sub
Private Sub TestArrayList(B yVal lst As ArrayList)
lst.Add(1)
lst.Add(1)
lst.Add(1)
End Sub
When I wrote it, I was sure to see in the message box that the ArrayList
have 2 items, because TestArrayList use the "lst" parameter ByVal. But, when
I ran that, I saw in the message box that the arraylist have 5 items....
Can you explain me what append here ?
Thanks a lot
Michel 3 1331
ByVal refers to the variable. For objects, it means a copy of the pointer to
the object is passed, as opposed to the original pointer. Meaning if you
were to say lst = Nothing, the x variable would not be effected. If you were
to pass ByRef, 'x' would actually be Nothing after the function call.
Under no conditions would the entire object ever be copied - not only would
this be a performance and memory nightmare, but often times it would raise a
lot of questions about whether object that this object points to needs to be
copied, etc.
"Michel" <Mi****@discuss ions.microsoft. com> wrote in message
news:1C******** *************** ***********@mic rosoft.com... Hi all, I wrote this sample code :
Private Sub Button1_Click( ..... ) Handles Button1.Click Dim x As New ArrayList x.Add(1) x.Add(1) TestArrayList(x ) MsgBox("TestArr ayList : " & x.Count.ToStrin g) End Sub
Private Sub TestArrayList(B yVal lst As ArrayList) lst.Add(1) lst.Add(1) lst.Add(1) End Sub
When I wrote it, I was sure to see in the message box that the ArrayList have 2 items, because TestArrayList use the "lst" parameter ByVal. But, when I ran that, I saw in the message box that the arraylist have 5 items....
Can you explain me what append here ?
Thanks a lot
Michel
Because although you are passing the array ByVal, an array is a Reference
Type. When you pass a reference type ByVal, you are not passing a copy of
the reference type, but instead you are passing a copy of the pointer to the
original reference type. You wind up with 2 pointers (in your case: x and
lst) that point to just one object (your array).
Only when you pass a value type (integer, date, Boolean, decimal, etc.)
ByVal do you get a copy of the data to work with.
"Michel" <Mi****@discuss ions.microsoft. com> wrote in message
news:1C******** *************** ***********@mic rosoft.com... Hi all, I wrote this sample code :
Private Sub Button1_Click( ..... ) Handles Button1.Click Dim x As New ArrayList x.Add(1) x.Add(1) TestArrayList(x ) MsgBox("TestArr ayList : " & x.Count.ToStrin g) End Sub
Private Sub TestArrayList(B yVal lst As ArrayList) lst.Add(1) lst.Add(1) lst.Add(1) End Sub
When I wrote it, I was sure to see in the message box that the ArrayList have 2 items, because TestArrayList use the "lst" parameter ByVal. But, when I ran that, I saw in the message box that the arraylist have 5 items....
Can you explain me what append here ?
Thanks a lot
Michel
"Michel" wrote: Hi all, I wrote this sample code :
Private Sub Button1_Click( ..... ) Handles Button1.Click Dim x As New ArrayList x.Add(1) x.Add(1) TestArrayList(x ) MsgBox("TestArr ayList : " & x.Count.ToStrin g) End Sub
Private Sub TestArrayList(B yVal lst As ArrayList) lst.Add(1) lst.Add(1) lst.Add(1) End Sub
When I wrote it, I was sure to see in the message box that the ArrayList have 2 items, because TestArrayList use the "lst" parameter ByVal. But, when I ran that, I saw in the message box that the arraylist have 5 items....
Can you explain me what append here ?
Thanks a lot
Michel
This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
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Hello!
Help!!!!
I have ten zillion books that attempt to describe the
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clear to me. I have gathered that ByVal makes a copy and
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Ok here is the senerio:
.....
Dim myArrayList as New ArrayList(0)
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