Re: comparing objects
- From: "netnet" <newsabcabc@xxxxxxxxxxx>
- Date: Mon, 23 Oct 2006 23:30:48 -0400
Arne / Dave,
Thanks for your feedback. I override the Equal method on SalesRegion
and all works as expected. Thanks Again.
"Dave Sexton" <dave@jwa[remove.this]online.com> wrote in message
news:OhOvKeX9GHA.4708@xxxxxxxxxxxxxxxxxxxxxxx
Hi,
Then it seems that this method is the source of your problem:
((InvoiceLineItem)i.invoiceLineItems[0]).getAllSalesRegionsThatAreSelectedInTheActiveCollection();
I think that the method is creating a different collection of objects than
the
getAllActiveSalesRegionsCached method, and you're trying to compare the
objects at the same indices in each collection via the Contains method.
As Arne already put it, the Contains method is using the Equals method,
which
checks for reference equality on objects. If each collection contains
different object instances then Contains will not work in the way that you
are
trying to use it.
Your best bet I think is to ensure that the
getAllSalesRegionsThatAreSelectedInTheActiveCollection uses the same
object
references as the getAllActiveSalesRegionsCached method.
--
Dave Sexton
"netnet" <newsabcabc@xxxxxxxxxxx> wrote in message
news:%23RbcEUX9GHA.3736@xxxxxxxxxxxxxxxxxxxxxxx
Hi Dave,
I tried both session and cache (in this scenario it wouldnt matter if
it was at an app or user level) and the results are the same. In both
cases below cached and uncached the result is 5 objects. They appear to
be the same objects but somehow using uncached the Contains logic works
properly. When using the cached version the objects are somehow different
and Contains always answers false.
"Dave Sexton" <dave@jwa[remove.this]online.com> wrote in message
news:O85ur7W9GHA.2288@xxxxxxxxxxxxxxxxxxxxxxx
Hi,
Originally, you wrote that you were storing the collection in the
session. The cache is quite different from the session and may actually
be causing the unexpected behavior you are observing.
After the following line is executed
ArrayList salesRegions = SalesRegion.getAllActiveSalesRegionsCached();
is salesRegions null? What is the count otherwise?
If you change the line to read as follows
ArrayList salesRegions =
SalesRegions.getAllActiveSalesRegionsUncached();
is salesRegions null? What is the count otherwise?
--
Dave Sexton
"netnet" <newsabcabc@xxxxxxxxxxx> wrote in message
news:uci2$mS9GHA.4196@xxxxxxxxxxxxxxxxxxxxxxx
Sorry I didnt provide more detail Cor....Heres an example of what im
doing...
//begin code to put collection in cache on SalesRegion class
public static IList getAllActiveSalesRegionsCached()
{
if( System.Web.HttpContext.Current.Cache["getAllActiveSalesRegions"]
== null)
resetCacheOfAllActiveSalesRegions();
return
(ArrayList)System.Web.HttpContext.Current.Cache["getAllActiveSalesRegions"];
}
public static void resetCacheOfAllActiveSalesRegions()
{
System.Web.HttpContext.Current.Cache["getAllActiveSalesRegions"] =
SalesRegion.getAllActiveSalesRegionsQuery();
}
public static IList getAllActiveSalesRegionsUncached()
{
return getAllActiveSalesRegionsQuery();
}
private static IList getAllActiveSalesRegionsQuery()
{
string theQuery = "from SalesRegion s where s.active = true";
return Db.Session.CreateQuery(theQuery).List();
}
//end code cache logic....
//then this is where i use the cached collection in a code behind...
ArrayList salesRegions = SalesRegion.getAllActiveSalesRegionsCached();
ArrayList allSelectedRegionsInActiveCollection =
((InvoiceLineItem)i.invoiceLineItems[0]).getAllSalesRegionsThatAreSelectedInTheActiveCollection();
for(int x=0; x<salesRegions.Count; x++)
{
if(allSelectedRegionsInActiveCollection.Contains(
((SalesRegion)salesRegions[x]) ) )
row.Add("X");
else
row.Add("");
cnt++;
}
if i use the uncached version the contains logic works fine but if i
use the cached version contains fails....
thanks again for all your help
"Arne Vajhøj" <arne@xxxxxxxxxx> wrote in message
news:jSp_g.22672$2g4.4823@xxxxxxxxxxxxx
netnet wrote:
No? Could you go into more detail? Im actually using the
myCol.Contains(foo) method.
Contains uses Equals to see if objects are identical (and
some other ways, but Equals is probably the most relevant for you).
If you have not implemented Equals, then it uses Object Equals,
which just test if it is the same object (same location in memory) -
not
if the values are the same.
To illustrate the point try and run the following code:
using System;
using System.Collections.Generic;
namespace E
{
public class A
{
private string s;
public A() : this("")
{
}
public A(string s)
{
this.s = s;
}
public string S
{
get
{
return s;
}
set
{
this.s = value;
}
}
public override string ToString()
{
return s;
}
}
public class B
{
private string s;
public B() : this("")
{
}
public B(string s)
{
this.s = s;
}
public string S
{
get
{
return s;
}
set
{
s = value;
}
}
public override string ToString()
{
return s;
}
public override bool Equals(object o)
{
if (o is B)
{
if (s == ((B)o).S)
{
return true;
}
else
{
return false;
}
}
else
{
return false;
}
}
public override int GetHashCode()
{
return s.GetHashCode();
}
}
public class MainClass
{
public static void Main(string[] args)
{
List<A> lst1 = new List<A>();
lst1.Add(new A("test"));
Console.WriteLine(lst1.Contains(new A("test")));
List<B> lst2 = new List<B>();
lst2.Add(new B("test"));
Console.WriteLine(lst2.Contains(new B("test")));
}
}
}
(it is using generics, but that nothing to do with the effect)
Arne
.
- References:
- comparing objects
- From: netnet
- Re: comparing objects
- From: Arne Vajhøj
- Re: comparing objects
- From: netnet
- Re: comparing objects
- From: Arne Vajhøj
- Re: comparing objects
- From: netnet
- Re: comparing objects
- From: Dave Sexton
- Re: comparing objects
- From: netnet
- Re: comparing objects
- From: Dave Sexton
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