[RESOLVED] [2005] creating a custom array type with .count property

Heya,

I have created a structure;

Code:

---

  Structure Server
        Public ServerName As String
        Public IpAddress As String

    End Structure

---

And I want a array of servers in a domain structure:

Code:

---

    Structure Domain
        Public Name As String
        Public Servers() As Server
    End Structure

---

But this does not support the 'domain.servers.count' property. I really need a the .count thing.

What is the best way of solving this? I don't want to use a 'sortedlist' because I don't want to use 'keys'. Should I make a custom 'array' type, or is it best to use another type to hold the servers? I also need to be able to 'for each' true the servers like:

Code:

---

for each MyServer as Server in MyDomain.Servers

---

Thanks in advance...

you can use

vb.net Code:

for i as integer = 0 to myDomain.Servers.Length-1
  dim s as Server = myDomain.Servers(i)
  'your code on the server here.
next i

or in the structure

vb.net Code:

Structure Domain
  public name as string
  public ServerList as List(of Servers) = nothing  
End Structure
 
for each s as Server in MyDomain.Servers
   'ýour code on the server here
next s

I dont understand your question, arrays do not have a 'Count' property in .Net 2.0 (in 3.5 they have an extension method called Count, but thats irrelevant here), but Length will, as talkro showed, return the arrays length.
So if you create a domain structure:

VB.NET Code:

Dim myDomain As New Domain

you can access its length property like so:

VB.NET Code:

myDomain.Servers.Length

Thanks Talkro, Atheistn,

The List seems to work.

If it is not to much to ask, when does one pick to use an:
list
sortedlist
collection

Whats the difference?

List(Of T) and SortedList are two types of collections (and there are many more), and you should choose whatever fits your situation the best.
A List(Of T) is the best all-round collection, but if you need the contents to be sorted by each elements key you should use a SortedList.
Note that there are two types of SortedLists:
SortedList and SortedList(Of TKey, TValue), you should choose the latter.

In addition to this issue, something new came up.

I'm using list(Of Server) now, and I'm for eaching true each member;

Code:

---

Structure Server
  public name as string
  public LastSeen as Date
End Structure

Structure Domain 
  public name as string
  public ServerList as List(of Servers) = nothing 
End Structure

for each s as Server in MyDomain.Servers
  s.lastseen = now
next

---

S as server is modified, but the value in mydomain.servers isn't because its read only.

Anny tips on solving this?

What do you mean by readonly? Could you show us the exact code you're using because what you've posted isnt 100% correct.

You should be aware of that structures are value-types so your loop isnt going to affect the original server instances in the List(Of Server)

Here's the exact code;

And I think I allready solved it, this now works:

Code:

---

    Structure Server
        Dim Name As String
        Dim Ipadress As String
        Dim LastSuccesPing As Date
        Dim LastFailedPing As Date
        Dim CurrentlyOnline As Boolean

    End Structure

    Public Servers As New SortedList(Of String, Server)

      For Each ServerKey As String In Servers.Keys

            Dim MyServer As Server = Servers(ServerKey)

            MyServer.LastSuccesPing = Now
            MyServer.CurrentlyOnline = True

            Servers(ServerKey) = MyServer

      Next

---

But this seems to me like old-skool programming, isn't this possible in an other way, without having to put back the value (servers(serverkey)=myserver)?

I'm looking for a conceptial tips, not a exact code example, if someone has a smarter way of doing this, please let me know!

Thanks in advance....

Quote:

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Originally Posted by Lectere

But this seems to me like old-skool programming, isn't this possible in an other way, with having to put back the value (servers(serverkey)=myserver?

Thanks in advance....

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Not when dealing with value-types. If you changed your structure to be a class instead, then you wouldnt have to put it back into the List, because you would be operating on the same object reference all the time.

I was wrong, this doesn't work... I get this:

Code:

---

Collection was modified after the enumerator was instantiated.

---

Ah yes of course, you would have to use a normal For loop instead of a For Each loop.

Thanks,

With this:

Code:

---

    Class Server
        Public Name As String
        Public Ipadress As String
        Public LastSuccesPing As Date
        Public LastFailedPing As Date
        Public CurrentlyOnline As Boolean

    End Class

    Public Servers As New SortedList(Of String, Server)

      For Each MyServer As Server In Servers.Values

            MyServer.LastSuccesPing = Now
            MyServer.CurrentlyOnline = True

      Next

---

It now works! thanks, but to be honest I'm don't understand it for 100%, does this has something to to with the byval,byref difference?

When working with a class, do I get a pointer to the instance? And working with a structure, I get a map of the structure, and not exactly the instance of this structure?

When you create an instance of a class, the variable will not hold the actual data contained in the class, but rather a memory address to where the data is located.
When you're using a structure, you the variable holds the actual values contained within the structure, and whenever you retrieve a structure from a list (like you did before), you get an exact copy of the structure, and not a reference to the original structure.

So in general it's never wise to use structures?, It seems old style programming.

Or can you name an example on why one should use a structure instead of a class?

For staters; A structure cannot contain methods... nore effectively encapsulate data. so if you require neither then a structure would be fine...