Remove object from a collection

[Tony Johansson]

Hello!

I have a collection with a lot of object.
Each object has the following definition.
public class ParametermappingObj
{
private string Name {get;set;}
private string Id {get;set;}
some other field defined here
....
}

If I know for example want to remove object with the following key values
Name = "CC" and Id = "123-CHISI" how is that done ?

Is there a better way then to loop through the whole collection

//Tony

[Tony Johansson]

Hello!

I forgot to say that I use VS2008 and the collection consist of a generic
List<ParametermappingObj>

//Tony
"Tony Johansson" <t.*********@logica.comwrote in message
news:ez**************@TK2MSFTNGP03.phx.gbl...

Hello!

I have a collection with a lot of object.
Each object has the following definition.
public class ParametermappingObj
{
private string Name {get;set;}
private string Id {get;set;}
some other field defined here
...
}

If I know for example want to remove object with the following key values
Name = "CC" and Id = "123-CHISI" how is that done ?

Is there a better way then to loop through the whole collection
//Tony

[=?ISO-8859-1?Q?G=F6ran_Andersson?=]

Tony Johansson wrote:

Hello!

I forgot to say that I use VS2008 and the collection consist of a
generic List<ParametermappingObj>

//Tony
"Tony Johansson" <t.*********@logica.comwrote in message
news:ez**************@TK2MSFTNGP03.phx.gbl...

>Hello!

I have a collection with a lot of object.
Each object has the following definition.
public class ParametermappingObj
{
private string Name {get;set;}
private string Id {get;set;}
some other field defined here
...
}

If I know for example want to remove object with the following key values
Name = "CC" and Id = "123-CHISI" how is that done ?

Is there a better way then to loop through the whole collection
//Tony

No, there is no other way to locate an item in the list other than
looping through the items in the list.

You can use the RemoveAll method to remove specific items:

theMappingList.RemoveAll(delegate(Parametermapping Obj p){ return p.Name
== "CC" && p.Id == "123-CHISI"; });

However, if you know that there is only one item to remove, it's more
efficient to do the looping yourself, so that you can exit from the loop
as soon as you have found the item to remove.

--
Göran Andersson
_____
http://www.guffa.com

[Jibesh]

Tony,

You can also try Predicate method of List<T>.Remove(...), This method also
searching through the list elements. Read MSDN for more details.

eg:
public class ParametermappingObj
{
private string _name;
public ParametermappingObj(string name)
{
_name = name;
}
public string Name
{
get { return this._name; }
set { this._name = value; }
}
}

public partial class MyClass

{

static string id = "aa";

public MyClass()

{

List<ParametermappingObjmyList = new List<ParametermappingObj>();

ParametermappingObj aa = new ParametermappingObj("aa");

ParametermappingObj bb = new ParametermappingObj("bb");

myList.Add(aa);

myList.Add(bb);

ParametermappingObj sublist = myList.Find(FindId); // myList.Remove(FindId)

}

public static bool FindId(ParametermappingObj obj){

if (obj.Name == id){ return true; }

return false;

}

}

Thanks
Jibesh
"Göran Andersson" <gu***@guffa.comwrote in message
news:%2****************@TK2MSFTNGP02.phx.gbl...

Tony Johansson wrote:

>Hello!

I forgot to say that I use VS2008 and the collection consist of a generic
List<ParametermappingObj>

//Tony
"Tony Johansson" <t.*********@logica.comwrote in message
news:ez**************@TK2MSFTNGP03.phx.gbl...

>>Hello!

I have a collection with a lot of object.
Each object has the following definition.
public class ParametermappingObj
{
private string Name {get;set;}
private string Id {get;set;}
some other field defined here
...
}

If I know for example want to remove object with the following key
values
Name = "CC" and Id = "123-CHISI" how is that done ?

Is there a better way then to loop through the whole collection
//Tony

No, there is no other way to locate an item in the list other than looping
through the items in the list.

You can use the RemoveAll method to remove specific items:

theMappingList.RemoveAll(delegate(Parametermapping Obj p){ return p.Name ==
"CC" && p.Id == "123-CHISI"; });

However, if you know that there is only one item to remove, it's more
efficient to do the looping yourself, so that you can exit from the loop
as soon as you have found the item to remove.

--
Göran Andersson
_____
http://www.guffa.com

[Ignacio Machin ( .NET/ C# MVP )]

On Oct 3, 10:04 am, "Tony Johansson" <[e-mail]:

Hello!

I have a collection with a lot of object.
Each object has the following definition.
public class ParametermappingObj
{
private string Name {get;set;}
private string Id {get;set;}
some other field defined here
...

}

If I know for example want to remove object with the following key values
Name = "CC" and Id = "123-CHISI" how is that done ?

Is there a better way then to loop through the whole collection

//Tony

No, you have to iterate on the collection but you can do it in an
elegant way :)
List<ParametermappingObjlist = new .....
......
ParametermappingObj element = null;
element = list.Find( x=>x.Name == "CC" && x.Id="123-CHISI");
if (element!= null)
list.Remove(element);

[Ignacio Machin ( .NET/ C# MVP )]

On Oct 3, 10:46 am, Göran Andersson <[e-mail]:

Tony Johansson wrote:

Hello!

I forgot to say that I use VS2008 and the collection consist of a
generic List<ParametermappingObj>

//Tony

"Tony Johansson" <[e-mail] in message
news:ez**************@TK2MSFTNGP03.phx.gbl...

Hello!

I have a collection with a lot of object.
Each object has the following definition.
public class ParametermappingObj
{
private string Name {get;set;}
private string Id {get;set;}
some other field defined here
...
}

If I know for example want to remove object with the following key values
Name = "CC" and Id = "123-CHISI" how is that done ?

Is there a better way then to loop through the whole collection
//Tony

No, there is no other way to locate an item in the list other than
looping through the items in the list.

You can use the RemoveAll method to remove specific items:

theMappingList.RemoveAll(delegate(Parametermapping Obj p){ return p.Name
== "CC" && p.Id == "123-CHISI"; });

However, if you know that there is only one item to remove, it's more
efficient to do the looping yourself, so that you can exit from the loop
as soon as you have found the item to remove.

--
Göran Andersson
_____http://www.guffa.com

You can use LINQ in a very elegant way. it will iterate until the
element is found for the first time.

[Peter Duniho]

On Fri, 03 Oct 2008 12:41:35 -0700, Ignacio Machin ( .NET/ C# MVP )
<ig************@gmail.comwrote:

You can use LINQ in a very elegant way. it will iterate until the
element is found for the first time.

In what way is that an improvement over calling Find() and then Remove()?
And is it as efficient as doing the enumeration explicitly, keeping a
counter, and then removing the element by index?

Do you have a code example that illustrates how LINQ can solve the problem
more elegantly?

Pete

[Peter Duniho]

On Thu, 02 Oct 2008 17:01:35 -0700, Jibesh <ji*******@gmail.comwrote:

Tony,

You can also try Predicate method of List<T>.Remove(...), This method
also
searching through the list elements. Read MSDN for more details.

There is no such method, and in fact in the code you posted, you did not
use any such method. The only Remove() method takes an object reference,
not a predicate.

For a single element one could use the "Find" method as the code you
posted does, but that's not as efficient as doing the loop explicitly as
Göran suggests.

There is a List<T>.RemoveAll() method that does the looping for you, but
that's exactly what Göran already suggested.

Pete

[Jibesh]

Thanks Pete.

sorry i miss typed it.

Its RemoveAll and not Remove. Remove only accepts reference and not
Predicate as you said.
Regards,
Jibesh

"Peter Duniho" <Np*********@nnowslpianmk.comwrote in message
news:op***************@petes-computer.local...

On Thu, 02 Oct 2008 17:01:35 -0700, Jibesh <ji*******@gmail.comwrote:

>Tony,

You can also try Predicate method of List<T>.Remove(...), This method
also
searching through the list elements. Read MSDN for more details.

There is no such method, and in fact in the code you posted, you did not
use any such method. The only Remove() method takes an object reference,
not a predicate.

For a single element one could use the "Find" method as the code you
posted does, but that's not as efficient as doing the loop explicitly as
Göran suggests.

There is a List<T>.RemoveAll() method that does the looping for you, but
that's exactly what Göran already suggested.

Pete

[Ignacio Machin ( .NET/ C# MVP )]

On Oct 3, 3:46 pm, "Peter Duniho" <[e-mail]>
wrote:

On Fri, 03 Oct 2008 12:41:35 -0700, Ignacio Machin ( .NET/ C# MVP )

<[e-mail]:

You can use LINQ in a very elegant way. it will iterate until the
element is found for the first time.

In what way is that an improvement over calling Find() and then Remove()?
And is it as efficient as doing the enumeration explicitly, keeping a
counter, and then removing the element by index?

More code?
Other than that there should be no difference, there is no other way
than iterate until find it, break the loop and then remove it. As I
said there is no other way around it

[Peter Duniho]

On Fri, 03 Oct 2008 13:29:54 -0700, Ignacio Machin ( .NET/ C# MVP )
<ig************@gmail.comwrote:

[...]

You can use LINQ in a very elegant way. it will iterate until the
element is found for the first time.

In what way is that an improvement over calling Find() and then
Remove()?
And is it as efficient as doing the enumeration explicitly, keeping a
counter, and then removing the element by index?

More code?

More code than what? So far, you haven't posted any LINQ code at all.

Other than that there should be no difference, there is no other way
than iterate until find it, break the loop and then remove it. As I
said there is no other way around it

Calling Find() followed by Remove() enumerates the list (up to the desired
element) twice. Writing the loop explicitly allows for doing the
enumeration just once.

I'm still confused by your comment about LINQ. I don't see how LINQ comes
into it.

Pete