ListView Sorting based on Subitem integer

[Shaddow]

I have my listview implimented, working. colored to my hearts content.... working on sorting and have implimented a class called ListViewItemComparer. (as seen in MSDN, here and other places). the sorting works..... kind of.. it sorts based on the input being a string. I however want it to sort based on it being an integer.

(ie. the following sort issue happens:

 

1, 2, 3, 4, 5, 6, 21, 33

 

results in: 1, 2, 21, 3, 33, 4, 5, 6

 

I am thinking that a solution falls into 1 or both of 2 categories.

 

1. possibly rewriting the ListviewItemComparer. and maybe funkifying some functions that will allow an 'extra' parameter to allow some specific casting

 

or

 

2. I should beat my head against the table and then try someone 'elses' simpler solution....

 

anyone ?

 

Thanks

[Bucky]

If it's not a problem to display the SubItems with excess 0's,

just concatenate an extra 0 on the front of the single-digit

values. Then it will sort correctly.

[PlausiblyDamp]

What code do you have at he moment for the comparison? It may be quite easy to convert.

[Shaddow]

Public Function Compare(ByVal x As Object, ByVal y As Object) As Integer _

Implements IComparer.Compare

Return [string].Compare(CType(x, ListViewItem).SubItems(col).Text, CType(y, ListViewItem).SubItems(col).Text)

End Function

 

 

 

This is in the class. and what actually compares the two.

[PlausiblyDamp]

Instead of casting the items to strings could you not convert the subitems to integers and then do the comparison.

 

not exactly sure of your requirements but something like the following may be a starting point.

Public Function Compare(ByVal x As Object, ByVal y As Object) As Integer _
Implements IComparer.Compare

Dim lv1, lv2 as ListViewItem
lv1 = directcast(x, ListViewItem)
lv2 = directcast(y, ListViewItem)

if integer.parse(lv1.SubItems(col).Text) > integer.parse(lv2.SubItems(col).Text ) then return 1
if integer.parse(lv1.SubItems(col).Text) < integer.parse( lv2.SubItems(col).Text) then return -1
return 0
End Function

[Shaddow]

works fantastic. however (isn't there always a however?) this would invalidate any sorting by any other column that might actually be textual. Is there some way to overload the compare function?

[PlausiblyDamp]

Not that I'm aware of (doesn't mean there isn't).

however you could check to see if x and y contain strings or integers and use the appropriate compare routines.

 

if typeof x is string and typeof y is string then
   'Do string compare
end if

if typeof x is integer and typeof y is integer then
   'Do integer compare
end if

[Shaddow]

this last part doesn't work. I believe it is because objects are passed not either integers or strings. i tried the code but It never executes. I think that its rather close to what I'll end up using. once I can do a quick determination on if the column is numeric or character based.

[Shaddow]

This seems to work. (I'm sure it wouldn't if the data processed wasn't integer(but still numeric).) however inelegant. I'll probably play with this a bit more to cover some more cases and a definite default to string if everything else doesn't work...

 

Public Function Compare(ByVal x As Object, ByVal y As Object) As Integer _

Implements IComparer.Compare

 

Dim lv1, lv2 As ListViewItem

lv1 = DirectCast(x, ListViewItem)

lv2 = DirectCast(y, ListViewItem)

Dim holder1, holder2, comptype As String

 

holder1 = lv1.SubItems(col).Text

holder2 = lv2.SubItems(col).Text

 

If IsNumeric(holder1) And IsNumeric(holder2) Then

comptype = "int"

Else

comptype = "str"

End If

If comptype = "str" Then

'Do string compare

Return [string].Compare(CType(x, ListViewItem).SubItems(col).Text, CType(y, ListViewItem).SubItems(col).Text)

End If

If comptype = "int" Then

'Do integer compare

If Integer.Parse(lv1.SubItems(col).Text) > Integer.Parse(lv2.SubItems(col).Text) Then Return -1

If Integer.Parse(lv1.SubItems(col).Text) < Integer.Parse(lv2.SubItems(col).Text) Then Return 1

Return 0

End If

' End If

 

End Function