Sorting strings as numeric

[amber]

Hello,
Is there a simple way to sort a listbox that contains strings that are
numbers?
My listbox is populated from a database field that has a datatype of string,
but typically contains numbers.
(I need to keep them as strings because occasionally they will have a letter
after them - 1a for ex).
I don't want zeros in front of them, I just want them to sort like this:
1
2
10
11
20
instead of 1
10
11
2
20

Possible??
Thanks in advance.
Amber

[Morten Wennevik]

Hi Amber,

You can do this easily by creating your own sorting rules, and in your case it is very simple.
It may even be possible to implement this in a databinding although I'm not sure how.
string[] strings = new string[]{
"1",
"10",
"11",
"2",
"20"
};

Array.Sort(strings, new MyComparer());
listBox1.AddRange(strings);

....

public class MyComparer : IComparer
{
public int Compare(object x, object y)
{
try
{
// strip away any trailing letters
// for instance, if nx.CompareTo(ny) returns 0,
// then compare the trailing letters using string.CompareTo
int nx = Int32.Parse((string)x);
int ny = Int32.Parse((string)y);
return nx.CompareTo(ny);
}
catch
{
return 0;
}
}
}
On Thu, 26 May 2005 18:58:09 +0200, amber <am***@discussions.microsoft.com> wrote:

Hello,
Is there a simple way to sort a listbox that contains strings that are
numbers?
My listbox is populated from a database field that has a datatype of string,
but typically contains numbers.
(I need to keep them as strings because occasionally they will have a letter
after them - 1a for ex).
I don't want zeros in front of them, I just want them to sort like this:
1
2
10
11
20
instead of 1
10
11
2
20

Possible??
Thanks in advance.
Amber

--
Happy coding!
Morten Wennevik [C# MVP]

[Morten Wennevik]

Hi Amber,

You can do this easily by creating your own sorting rules, and in your case it is very simple.
It may even be possible to implement this in a databinding although I'm not sure how.
string[] strings = new string[]{
"1",
"10",
"11",
"2",
"20"
};

Array.Sort(strings, new MyComparer());
listBox1.AddRange(strings);

....

public class MyComparer : IComparer
{
public int Compare(object x, object y)
{
try
{
// strip away any trailing letters
// for instance, if nx.CompareTo(ny) returns 0,
// then compare the trailing letters using string.CompareTo
int nx = Int32.Parse((string)x);
int ny = Int32.Parse((string)y);
return nx.CompareTo(ny);
}
catch
{
return 0;
}
}
}
On Thu, 26 May 2005 18:58:09 +0200, amber <am***@discussions.microsoft.com> wrote:

Hello,
Is there a simple way to sort a listbox that contains strings that are
numbers?
My listbox is populated from a database field that has a datatype of string,
but typically contains numbers.
(I need to keep them as strings because occasionally they will have a letter
after them - 1a for ex).
I don't want zeros in front of them, I just want them to sort like this:
1
2
10
11
20
instead of 1
10
11
2
20

Possible??
Thanks in advance.
Amber

--
Happy coding!
Morten Wennevik [C# MVP]

[Patrice]

The simplest solution solution I see would be to use two separate fields.
Server side you'll use ORDER BY num,letter to get the correct order...
Especially it"s worth to consider if the letter has some kind of meaning you
may want also to exploit at some other place(s).

Else you'll have to "process" these entries before sorting them (such as
ordering on a computed field that uses leading 0s for example by using ORDER
BY RIGHT("0000"+Field,4) or something similar depending on your DB (and for
example it won't use indexing etc...)

Patrice
--

"amber" <am***@discussions.microsoft.com> a écrit dans le message de
news:82**********************************@microsof t.com...

Hello,
Is there a simple way to sort a listbox that contains strings that are
numbers?
My listbox is populated from a database field that has a datatype of string, but typically contains numbers.
(I need to keep them as strings because occasionally they will have a letter after them - 1a for ex).
I don't want zeros in front of them, I just want them to sort like this:
1
2
10
11
20
instead of 1
10
11
2
20

Possible??
Thanks in advance.
Amber

[Patrice]

The simplest solution solution I see would be to use two separate fields.
Server side you'll use ORDER BY num,letter to get the correct order...
Especially it"s worth to consider if the letter has some kind of meaning you
may want also to exploit at some other place(s).

Else you'll have to "process" these entries before sorting them (such as
ordering on a computed field that uses leading 0s for example by using ORDER
BY RIGHT("0000"+Field,4) or something similar depending on your DB (and for
example it won't use indexing etc...)

Patrice
--

"amber" <am***@discussions.microsoft.com> a écrit dans le message de
news:82**********************************@microsof t.com...

Hello,
Is there a simple way to sort a listbox that contains strings that are
numbers?
My listbox is populated from a database field that has a datatype of string, but typically contains numbers.
(I need to keep them as strings because occasionally they will have a letter after them - 1a for ex).
I don't want zeros in front of them, I just want them to sort like this:
1
2
10
11
20
instead of 1
10
11
2
20

Possible??
Thanks in advance.
Amber

[Helge Jensen]

amber wrote:

I don't want zeros in front of them, I just want them to sort like this:
1
2
10 Possible??

Write an IComparer. Here is one (untested, from memory) that works
nicely on string-representations with other radix'es than 10:

class NumericStringComparer: IComparer {
public bool IgnoreCase = true;
// Some cultures sorts wierdly on i.e. "AA"
public System.Globalization.CultureInfo Culture =
System.Globalization.CultureInfo.InvariantCulture;
´ public int Compare(object x, object y) {
string s1 = (string)x;
string s2 = (string)y;
int l1 = s1.Length;
int l2 = s2.Length;
if ( l1 == l2 )
return string.Compare(
s1, 0, s2, 0, l1,
IgnoreCase,
Culture);
else
return l1 - l2;
}
}

This is a usefull class on it's own but does not solve the problem, for
that I normally use a "column-sorter", roughly like:

class ColumnSorter: IComparer {
public int Column;
IComparer Comparer;
public ColumnSorter(IComparer comparer, int column) {
this.Column = column;
this.Comparer = comparer;
}
public int Compare(object x, object y) {
return Comparer.Compare(
((ListViewItem)x).SubItems[Column].Text,
((ListViewItem)y).SubItems[Column].Text);
}
}

Which you can attach to the ListView using .ListViewItemSorter. It
allows you to change which column to sort by assigning to .Column.

There may be some null-value-checking required, I can't remember that
off the top of my head.

--
Helge Jensen
mailto:he**********@slog.dk
sip:he**********@slog.dk
-=> Sebastian cover-music: http://ungdomshus.nu <=-

[Helge Jensen]

amber wrote:

I don't want zeros in front of them, I just want them to sort like this:
1
2
10 Possible??

Write an IComparer. Here is one (untested, from memory) that works
nicely on string-representations with other radix'es than 10:

class NumericStringComparer: IComparer {
public bool IgnoreCase = true;
// Some cultures sorts wierdly on i.e. "AA"
public System.Globalization.CultureInfo Culture =
System.Globalization.CultureInfo.InvariantCulture;
´ public int Compare(object x, object y) {
string s1 = (string)x;
string s2 = (string)y;
int l1 = s1.Length;
int l2 = s2.Length;
if ( l1 == l2 )
return string.Compare(
s1, 0, s2, 0, l1,
IgnoreCase,
Culture);
else
return l1 - l2;
}
}

This is a usefull class on it's own but does not solve the problem, for
that I normally use a "column-sorter", roughly like:

class ColumnSorter: IComparer {
public int Column;
IComparer Comparer;
public ColumnSorter(IComparer comparer, int column) {
this.Column = column;
this.Comparer = comparer;
}
public int Compare(object x, object y) {
return Comparer.Compare(
((ListViewItem)x).SubItems[Column].Text,
((ListViewItem)y).SubItems[Column].Text);
}
}

Which you can attach to the ListView using .ListViewItemSorter. It
allows you to change which column to sort by assigning to .Column.

There may be some null-value-checking required, I can't remember that
off the top of my head.

--
Helge Jensen
mailto:he**********@slog.dk
sip:he**********@slog.dk
-=> Sebastian cover-music: http://ungdomshus.nu <=-