iequalitycompar er help

[psawant]

Hi all,

I have a custom colllelctoin class which inherits collecton base.
It is a collecton of objects of type X and X has ID integer as like a
unique key.

How do i check if the object already exists in the collection?.

I think i am missing something straightfoward.

Thanks for your input.

[Dave Sexton]

Hi,

If your object derives from System.Collecti ons.CollectionB ase then you'll have
to iterate the entire collection and compare each item individually.

You could do something like this instead:

public class XCollection : List<X>
{
public bool Exists(X x)
{
return Exists(delegate (X x1)
{
return x.ID == x1.ID;
});
}
}

If your object is more like a value-type, then make it an immutable struct and
override the Equals method. Then you'll be able to use X in lists as if it
were the ID that it contains - meaning you won't need to use the code above at
all. If you make a struct then you should also override GetHashCode and
create operator overloads for == and != as well:

--
Dave Sexton

<ps*****@gmail. comwrote in message
news:11******** *************@f 16g2000cwb.goog legroups.com...

Hi all,

I have a custom colllelctoin class which inherits collecton base.
It is a collecton of objects of type X and X has ID integer as like a
unique key.

How do i check if the object already exists in the collection?.

I think i am missing something straightfoward.

Thanks for your input.

[Dave Sexton]

Hi,

I just realized that you mentioned ID is an integer, which means you might be
able to increase the performance of the search by using List<Xand calling
Sort, then BinarySearch and supplying to both a custom IComparer<X>
implementation that compares on the ID property. You could modify my
XCollection example to encapsulate that functionality in Exists(X), for
instance. Then you probably shouldn't derive from List<Xbut instead
composite it.

HTH

--
Dave Sexton

"Dave Sexton" <dave@jwa[remove.this]online.comwrote in message
news:u5******** ******@TK2MSFTN GP04.phx.gbl...

Hi,

If your object derives from System.Collecti ons.CollectionB ase then you'll
have to iterate the entire collection and compare each item individually.

You could do something like this instead:

public class XCollection : List<X>
{
public bool Exists(X x)
{
return Exists(delegate (X x1)
{
return x.ID == x1.ID;
});
}
}

If your object is more like a value-type, then make it an immutable struct
and override the Equals method. Then you'll be able to use X in lists as if
it were the ID that it contains - meaning you won't need to use the code
above at all. If you make a struct then you should also override
GetHashCode and create operator overloads for == and != as well:

--
Dave Sexton

<ps*****@gmail. comwrote in message
news:11******** *************@f 16g2000cwb.goog legroups.com...

>Hi all,

I have a custom colllelctoin class which inherits collecton base.
It is a collecton of objects of type X and X has ID integer as like a
unique key.

How do i check if the object already exists in the collection?.

I think i am missing something straightfoward.

Thanks for your input.