Re: Combo Box question - C# Discussion Boards

10-Dec-06 23:05

Alrighty then, my new question is this:

I have a combo box in each user control, and I have several user controls. Now I want each combo box to start off with the same options availible to them, (e.g. Mike, 1, 2, 3, 4, 5. I know how to do this part.) but when an option other than Mike is chosen in a combo box, then none of the other combo boxes can choose that option.

So if ComboBox1 has selected 1, then ComboBox2 will only be able to select Mike, 2, 3, 4, 5. But if ComboBox1 has Mike selected, ComboBox2 will still be able to select Mike, 1, 2, 3, 4, 5.

Anyway, I think I can put something together using handlers and arrays to do this, however I was hoping that someone knew a better way (or better yet knew if there was an article about this).

I hope I made sense. Any help will be appreciated.

Edit:

Here's how I would go about the code for this function.

In the Master class (The one that's creating the User controls) there is an array (Array1) with the combo box values. There is a second array (Array2) with the values that haven't been used. Array2 is passed into the User controls on creation, allowing them to populate their combo boxes.

In the User control there is also public method which updates the contents of the Combo box.

Now in order to get the combo boxes to update on all of the other User controls, a handler is put in the User control that listens for when the combo box is changed. This handler passes the contents of the combo box from both before(Value1) and after(Value2) the change (probably useing variables in the User class) to the Master class (which has a handle listening for the User control handler).

The Master class then removes Value2 from Array2. Then the Master class adds Value1 to Array2. Once this is done the Master passes Array2 into the public methods of all user controls, which forces them to update their Combo Box contents. Note that when placing Value1 into the array, a while loop would be used in order to have it placed in the appropriate position.

I really hope that explanation made sense.

- Munty

-- modified at 5:47 Monday 11th December, 2006

Martin#11-Dec-06 0:14

11-Dec-06 0:14

Hello,

Thats what I would try to do:

I would implement an "ItemManager" which holds the Array of available Items.
This Manager has an event ItemsChanged which is raised if the Array is changed.

The UserControls then get the Instance (Only one instance for all Controls) of the Manager.
They also link to the event.

If then a item is selected in a combobox it has to be removed from the Array of the manager and the olditem has to be added again.

If the ItemsChanged Event of the Manager is raised, the UserControls have too rearange their available items.

Hope that helps!

All the best,

Martin

Muntyness11-Dec-06 0:43

11-Dec-06 0:43

Just one question.

I was assuming that ItemManager was a built in class, but as I can't find it, I'm now assuming that you meant I should make an Item manager myself. Other than that, I'm planning on trying that out sometime today.

- Munty

Martin#11-Dec-06 0:57

11-Dec-06 0:57

Muntyness wrote:
I'm now assuming that you meant I should make an Item manager myself.

Yes that's correct.
I was thinking of something like that:

public class ItemManager
{
    private static ItemManager _instance;
    private Array _availableitems = new Array();

    public ItemManager()
    {
    }

    public Array AvailableItems
    {
        get
        {
            return _availableitems;
        }
        set
        {
            if(value!=_availableitems)
            {
                _availableitems = value;
                //TODO: event for the Information of the UserControls
            }
        }
    }


    public static ItemManager GetInstance()
    {
        if(_instance==null)
        {
            _instance = new ItemManager();
        }
        return _instance;
    }
}

Hope that helps!

All the best,

Martin

Muntyness11-Dec-06 1:16

11-Dec-06 1:16

Aye, that helps alot.

Thanks!

- Munty

Muntyness11-Dec-06 6:26

11-Dec-06 6:26

Alrighty, Im here to bug you again.

So I took your framework and butchered it. (What can I say? I'm stupid Sigh | :sigh:

)

public class fnt_ItemManager
    {
        public event EventHandler ArrayChanged;
        private Array _availableitems;

        public fnt_ItemManager()
        {
        }

        public Array AvailableItems
        {
            get
            {
                return _availableitems;
            }
            set
            {
                if (value != _availableitems)
                {
                    _availableitems = value;
                }
            }
        }

        public void update (String oldVal, String newVal)
        {
            ArrayList updating = new ArrayList();
            int i = 1;

            if (oldVal != null)
            {
                foreach (String st in _availableitems)
                {
                    if (newVal != st || newVal == "#NONE")
                    {
                        updating.Add(st);
                    }
                }

                if (oldVal != "#NONE")
                {
                    Boolean found = false;
                    while (i < updating.Count)
                    {
                        if (int.Parse((String)updating[i]) > int.Parse(oldVal))
                        {
                            updating.Insert(i, oldVal);
                            found = true;
                            break;
                        }
                        i++;
                    }
                    if (oldVal != null && found == false)
                    {
                        updating.Add(oldVal);
                    }
                }


                String[] rar = new String[updating.Count];
                i = 0;

                foreach (String st in updating)
                {
                    rar[i] = st;
                    i++;
                }

                _availableitems = rar;

                if (ArrayChanged != null)
                {
                    ArrayChanged(this, EventArgs.Empty);
                }
            }
        }
    }
}

And in the control that calls it:

private void cmb1_SelectedIndexChanged(object sender, EventArgs e)
{
    OldValue = Current;
    Current = cmb1.Text;

    if (OldValue != null && OldValue != Current)
    {
        ItemManager.update(OldValue, Current);
    }
}

void p_ItemManager_ArrayChanged(object sender, EventArgs e)
{
    cmb1.Items.Clear();

    foreach (String st in p_ItemManager.AvailableItems)
    {
        cmb1.Items.Add(st);
    }            
}

Now then, this actually works for the most part, however it's kinda iffy (seems to call all the handlers in the control class twice). Plus in the combo boxes, while the code see's the values that are in the boxes, people can't. So the code would see that the box contained "5", however I'm only seeing "". Kinda iffy once again.

Sooo, is this worth keeping, or should I just scrap it all and take up farming now? D'Oh! | :doh:

- Munty

Martin#11-Dec-06 9:49

Re: Combo Box question [modified]

11-Dec-06 9:49

Hello Munty,

Muntyness wrote:
should I just scrap it all and take up farming now?

I think this would be the best solution for everyone! Laugh | :laugh:

My suggestions are:

UserControl:
Maybe the SelectedIndexChanged Event is raised to often because of the "Items.Clear" and "Items.Add".
So a boolen flag in the SelectedIndexChanged Method could help.

private bool updating;

private void cmbl_SelectedIndexChanged(object sender, EventArgs e)
{
if(updating==false)
{
OldValue = Current;
Current = cmb1.Text;
.
.
.
}
}

private void p_ItemManager_ArrayChanged(object sender, EventArgs e)
{
updating = true;

.
.
.

updating = false;
}

ItemManager:
Have you used the GetInstance Methode?

The update Method looks much too complicated for working correct.
Why cant't you just add and remove directly from the Array?

See you!

Martin

Muntyness12-Dec-06 3:19

12-Dec-06 3:19

Martin# wrote:
ItemManager:
Have you used the GetInstance Methode?

Admittedly no. To be honest I wasn't sure what that method was for... Confused | :confused:

Martin# wrote:
Why cant't you just add and remove directly from the Array?

I can directly remove from the array (it now does that Blush | :O

), it's just that when I add to the array, the items need to be ordered. So I can either put the value into the correct place to start with, or I can sort the array after the item has been added. I'm fairly sure that sorting the array after every change would probably be worse, but if it's better to sort, feel free to tell me.

the code now looks more like this:
(There are 2 combo boxes now, but the methods are identical except for some names)

private void cmb1_SelectedIndexChanged(object sender, EventArgs e)
        {
            OldValue1 = Current1;
            Current1 = cmb1.Text;

            if (OldValue1 != null && OldValue1 != Current1)
            {
                selected = 1;
                ItemManager.update(OldValue1, cmb1.SelectedIndex);
            }
        }

        void ItemManager_ArrayChanged(object sender, EventArgs e)
        {
            if (selected != 1)
                cmb1.Items.Clear();
            if (selected != 2)
                cmb2.Items.Clear();

            foreach (String st in p_ItemManager.AvailableItems)
            {
                if (selected != 1)
                    cmb1.Items.Add(st);
                if (selected != 2)
                    cmb2.Items.Add(st);
            }

            selected = 0;
        }

int the item manager:

public class fnt_ItemManager
{
    public event EventHandler ArrayChanged;
    private ArrayList _availableitems = new ArrayList();
    private String Default;
    
    public fnt_ItemManager(String defaultcont)
    {
        Default = defaultcont;
    }

    public ArrayList AvailableItems
    {
        get
        {
            return _availableitems;
        }
        set
        {
            if (value != _availableitems)
            {
                _availableitems = value;
            }
        }
    }

    public void update(String oldVal, int index)
    {
        Boolean found = false;
        int i = 0;

        if (index != 0)
        {
            AvailableItems.RemoveAt(index);
        }

        if (oldVal != Default)
        {
            foreach (String st in AvailableItems)
            {
                if (st.CompareTo(oldVal) > 0)
                {
                    AvailableItems.Insert(i, oldVal);
                    found = true;
                    break;
                }
                i++;
            }

            if (oldVal != null && found == false)
            {
                AvailableItems.Add(oldVal);
            }
        }

        if (ArrayChanged != null)
        {
            ArrayChanged(this, EventArgs.Empty);
        }
    }
}

It's better than before, but still buggy. (Go me! Frown | :(

- Munty

-- modified at 9:55 Tuesday 12th December, 2006

Martin#12-Dec-06 5:43

12-Dec-06 5:43

Hello Munty,

Muntyness wrote:
Admittedly no. To be honest I wasn't sure what that method was for.

This Method generates only one instance of the fnt_ItemManager.
It's also static, so you do not need an instance of the class to call it.

Cause if you make a instance like this:

fnt_ItemManager p_ItemManager = new fnt_ItemManager();

Every Control has its one instance of the Manager and has no idea which item is used by an other Control.

So please implement the method like i did and call it from the Controls, like that:

fnt_ItemManager p_ItemManager = yourenamespace.fnt_ItemManager.GetInstance();

If no't all controlls are linked (sharing one set of items), please let me know.
We would have to make the GetInstance method more dynamic to create and return more than one instance.

Hope that helps!

All the best,

Martin

Muntyness12-Dec-06 8:48