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Help with sorting an Arraylist that contains Structures

Ok, I give up. I can't seem to construct a decent (productive) way of
sorting my arraylist.

I have a structure of two elements:

Structure TabStructure
Dim TabName As String
Dim FullFilePath As String
End Structure

Then for example I:

Dim tab as New TabStructure

some code

Then I add "tab" to an arraylist.

At some point I loop through my arraylist, grab data and create tabs from
it. Of course the resulting list of tabs are out of sequence.

Can someone help me to sort my array list alphabetically by
TabStructure.Ta bName?

I would greatly appreciate it.

Aug 21 '08
12 9803
On 2008-08-22, Justin <No**@None.comw rote:
Ok, after getting beat in the head with "class" by 4 people I converted it
to a class :)

I tried to convert my arraylist to a list and that was just an ugly mess.
Here's the first two errors I received:
'TabsArray' cannot expose type 'TabClass' outside the project through class
'frmMain'
Too few type arguments to 'System.Collect ions.Generic.Li st(Of T)'

But enough of that. I want to wrap my head around iComparable first. I'll
deal with that later.

I implemented iComparable and now when I try to .sort my arraylist I get:

"Failed to compare two elements in the array."

Again, thanks for the help everyone!
Using a list should be simply:

Dim myList As New List(Of TabClass)()

from there, it is very much like an ArrayList - only better and faster :)

--
Tom Shelton
Aug 22 '08 #11
I've come across this before. When something as simple as this just isn't
working I've learned to start a whole new project and bring everything over.
Surprisingly that didn't take too long.

The error, "Failed to compare two elements in the array.", came over however
once I converted the arraylist to a list the error went away and it's now
sorting properly. Obviously the List errors did not come over as well.

I'm growing a little tired of having to start whole new projects because of
silly unexplained issues but at the same time I'm glad to be able to move
forward.

Again, thanks to everyone!
"Tom Shelton" <to*********@co mcastXXXXXXX.ne twrote in message
news:3I******** *************** *******@comcast .com...
On 2008-08-22, Justin <No**@None.comw rote:
>Ok, after getting beat in the head with "class" by 4 people I converted
it
to a class :)

I tried to convert my arraylist to a list and that was just an ugly mess.
Here's the first two errors I received:
'TabsArray' cannot expose type 'TabClass' outside the project through
class
'frmMain'
Too few type arguments to 'System.Collect ions.Generic.Li st(Of T)'

But enough of that. I want to wrap my head around iComparable first.
I'll
deal with that later.

I implemented iComparable and now when I try to .sort my arraylist I get:

"Failed to compare two elements in the array."

Again, thanks for the help everyone!

Using a list should be simply:

Dim myList As New List(Of TabClass)()

from there, it is very much like an ArrayList - only better and faster :)

--
Tom Shelton
Aug 22 '08 #12
Point well taken. While my data doesn't change so this wont hurt me here, I
never knew this about structures and I'll be sure to just use classes from
now on.

Thanks!
"Tom Shelton" <to*********@co mcastXXXXXXX.ne twrote in message
news:cM******** *************** *******@comcast .com...
On 2008-08-21, Justin <No**@None.comw rote:
>Ok, I give up. I can't seem to construct a decent (productive) way of
sorting my arraylist.

I have a structure of two elements:

Structure TabStructure
Dim TabName As String
Dim FullFilePath As String
End Structure

Then for example I:

Dim tab as New TabStructure

some code

Then I add "tab" to an arraylist.

At some point I loop through my arraylist, grab data and create tabs from
it. Of course the resulting list of tabs are out of sequence.

Can someone help me to sort my array list alphabetically by
TabStructure.T abName?

I would greatly appreciate it.

Others have point out to you the List(Of T) - so I won't rehash that :)
But,
I'm going to talk about your structure. The fact is, there is almost
never
any reason to use a structure except for interop scenarios or where you
want
to preserve value symantics... TabStructure should be a class. This will
become apparent as soon as you start trying to modify individual members
of
your list:

Private Structure TStruct
Public s1 As String
Public s2 As String

Public Sub New(ByVal s1 As String, ByVal s2 As String)
Me.s1 = s1
Me.s2 = s2
End Sub
End Structure

Sub Main()
Dim l As New List(Of TStruct)
l.Add(New TStruct("one", "one"))
l.Add(New TStruct("two", "one"))
l.Add(New TStruct("three" , "one"))
l.Add(New TStruct("four", "one"))

For Each i As TStruct In l
i.s2 = "changing.. ."
Next

For Each i As TStruct In l
Console.WriteLi ne("s1={0}, s2={1}", i.s1, i.s2)
Next
End Sub

You might be suprised that the values of s2 changend in the first loop,
don't
actually change anything. That's because TStruct is a value type, and any
time you assign or return it you get a copy and not the original. If I
change
TStruct to a class:

Private Class TStruct
Public s1 As String
Public s2 As String

Public Sub New(ByVal s1 As String, ByVal s2 As String)
Me.s1 = s1
Me.s2 = s2
End Sub
End Class

Then every thing works as expected.

So, again unless your doing interop or really want value symantics, there
is
not much gained by using a struct over a class.

--
Tom Shelton
Aug 23 '08 #13

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