Add items to list

Jay S

13y2kVisual Basic .NET

Currently I'm creating a list in "Form1" pretty much this:

//
//
this.Shortlist = new System.Collections.Generic.List();

this.ShortlistIndex = (int)binaryReader.BaseStream.Position;

for (i = 0; i < (int)shortlistnum; i++)

{

Shortlist item2 = new Shortlist(binaryReader);

this.Shortlist.Add(item2);

}

binaryReader.Close();

The Shortlist class is:

public class Shortlist

{

public string Name;

public string Nation;

public string NationalityName;

public int Age;

public Shortlist()

{

}

public Shortlist(System.IO.BinaryReader reader)

{

this.Name = reader.ReadString(128).Replace("\0", string.Empty);

}

All works fine..I then call another function (still in Form1) which joins this list with another list to create a 3rd list (and bind it to a listview):

private void Populate(object sender, EventArgs e)

{

var userlist = (from Item1 in Shortlist

join Item2 in People

on Item1.Name equals Item2.FullName

into grouping

from Item2 in grouping.DefaultIfEmpty()

select new

{Item2.FullName

,Item2.Age

,Item2.CountryName

,Item2.Nationality

}).ToList();

this.fastObjectListView3.SetObjects(userlist);

}

Again, happy with this, all is ok..

In "Form2" I have a button and when clicked I want to pass a pre-defined string/item/value/object...whatever you call it and add it into this.Shortlist (In Form1) and then my "Populate" function called to repopulate & bind my 3rd list.

I can't seem to work out how to add across classes..any help..Vulpes :p would be great

6 Replies

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Vulpes13y ago
Accepted answer
First change the access modifier of the ShortList field and Populate method of Form1 from private to internal so they can be accessed by other classes in the same application:

class Form1 : Form
{
internal List ShortList;

internal void Populate(object sender, EventArgs e)
{
// blah
}

// other code
}

Now in the button Click eventhandler on Form2 you'll need something like this:

private button1_Click(object sender, EventArgs e)
{
Form1 f1 = (Form1)Application.OpenForms["Form1"];
ShortList sl = new ShortList();
// set sl's properties
f1.ShortList.Add(sl);
f1.Populate(this, EventArgs.Empty); // say
}
0
Vulpes13y ago
That would work if you still had a reference (sl) to the object which you'd added to the List and now wanted to remove it

In the more general case, where you wanted to identify a particular ShortList object by Name property and then remove it from the List, you could use LINQ like this:

ShortList itemToRemove = f1.ShortList.Where(item => item.Name == "John").FirstOrDefault();
if (itemToRemove != null)
{
f1.Remove(itemToRemove);
f1.Populate(this, EventArgs.Empty);
}
0
Jay S13y ago
Ahh! Perfect!

Is there an easy/simple way to remove from the list..

So lets say I've added "John" from shortlist.

Is there a way to remove "John" and re-call populate() ?

Edit..maybe:

f1.Shortlist.Remove(sl); ?
0
Vulpes13y ago
Just do something like this :

ShortList sl = new ShortList();
sl.Name = "John";
sl.Nation = "Canada";
sl.NationalityName = "Canadian";
sl.Age = 30;
f1.ShortList.Add(sl);
0
Jay S13y ago
Vulpes..amazing as usual..I aspire to be as good as you..

One thing I'm not sure about is:

private button1_Click(object sender, EventArgs e)
{
Form1 f1 = (Form1)Application.OpenForms["Form1"];
ShortList sl = new ShortList();
// set sl's properties
f1.ShortList.Add(sl);
f1.Populate(this, EventArgs.Empty); // say
}

Specifically:

ShortList sl = new ShortList();
// set sl's properties
f1.ShortList.Add(sl);

If I'm adding "sl" how can I set that value before the add?

E.g. I want to add into the list the name "John"
0
Abhishek Sur13y ago
Why dont you make the List exposed outside the form. Make it a public member and also make the Populate function public.

From form2 call,

Form1.ShortList.Add(whatever);

And then call,

Form1.Populate();
0