Re: COMBO BOX ISSUE [modified] - C# Discussion Boards

spankyleo12317-Nov-09 2:57

17-Nov-09 2:57

Hi ALL,

I am dynamically adding items to a combobox using a text box and a button. The value gets populated into the combobox, but when I close the form and reopen it, the combobox has no values in it.

Is there any way in which i can view the added item after closing and reopening the form.

Thanks,

Re: COMBO BOX ISSUE

musefan17-Nov-09 3:01

musefan

17-Nov-09 3:01

You could create a static list which is also added to when you add to the comboBox, then use this list to populate the comboBox when the form is opened... FormShown event or something similar will do the trick

Life goes very fast. Tomorrow, today is already yesterday.

Re: COMBO BOX ISSUE

musefan17-Nov-09 3:10

musefan

17-Nov-09 3:10

1???

What's wrong with my suggestion?

Life goes very fast. Tomorrow, today is already yesterday.

Re: COMBO BOX ISSUE

EliottA17-Nov-09 3:15

EliottA

17-Nov-09 3:15

I tried to balance the negative feedback left.

Check out the CodeProject forum Guidelines[^]
The original soapbox 1.0 is back![^]

Re: COMBO BOX ISSUE

musefan17-Nov-09 3:17

musefan

17-Nov-09 3:17

Thanks

Life goes very fast. Tomorrow, today is already yesterday.

Re: COMBO BOX ISSUE

ragnaroknrol17-Nov-09 5:56

ragnaroknrol

17-Nov-09 5:56

I don't get the downvoting either.

Your suggestion is dead on. It would work just fine. No snarky answer and being helpful. You didn't deserve a 1.

Re: COMBO BOX ISSUE

musefan17-Nov-09 6:21

musefan

17-Nov-09 6:21

Thanks for your support Wink | ;)

Life goes very fast. Tomorrow, today is already yesterday.

Re: COMBO BOX ISSUE [modified]

spankyleo12317-Nov-09 22:22

spankyleo123

17-Nov-09 22:22

Thanks for ur suggestion...

I tried to load the list as assigned it to the combobox at form load.

private List<String> List = new List<string>();<br />
private void button2_Click(object sender, EventArgs e)<br />
        {<br />
          comboBox.Items.Add(textBox4.Text);<br />
                <br />
                List.Add(textBox4.Text);<br />
        }<br />
<br />
private void Form1_Load(object sender, EventArgs e)<br />
        {<br />
          this.comboBox.Items.Add(List);<br />
        }<br />

Am i doing it the right way??.... coz the combobox is empty again at form load..... I know am missing something.

Appreciate your response.....Thanks

modified on Wednesday, November 18, 2009 4:29 AM

Re: COMBO BOX ISSUE

musefan17-Nov-09 22:44

musefan

17-Nov-09 22:44

You need to make the list static, this means that the list will be the same for all instances of the form. No matter how many forms you create, there will only be one list. This way the list will only be cleared when the application is closed, not when the form is closed.

Change to this line...

private static List<String> List = new List<string>();

Life goes very fast. Tomorrow, today is already yesterday.

Re: COMBO BOX ISSUE

spankyleo12317-Nov-09 23:46

spankyleo123

17-Nov-09 23:46

okay Thanks for your reply.

I guess il have to create a table and populate the combobox from it.

DO you know how I can go about doing this using language integrated query?

Thanks,..

Re: COMBO BOX ISSUE

musefan18-Nov-09 0:03

musefan

18-Nov-09 0:03

What do you mean by table? What's wrong with the static method? Are you trying to keep the list when the application is closed?

I don't use LINQ (still not been converted), its fairly simple to write code that will access data (with the use of other .Net functions of course) and you get full control of how it works that way. How are you wanting to store the data?

Life goes very fast. Tomorrow, today is already yesterday.

Re: COMBO BOX ISSUE

spankyleo12323-Nov-09 21:29

spankyleo123

23-Nov-09 21:29

hello....

Thanks for your reply. Yes it would be beneficial to keep the items list when the application is closed and reopened. By table I mean that, I would want to create a table with one column containing the list of items which the combobox should have. And I want to load this column as the combobox data source. Because I want the user to add new entries into the combobox as and when required.

Re: COMBO BOX ISSUE

Shameel17-Nov-09 3:04

Shameel

17-Nov-09 3:04

First, you need to learn the basics of programming. Get a good book on C#.

The items you add to the combo box live only as long as your app is running. If you want to persist them, you need to write code to save the items to a data store such as a text file, an xml file or a database.

Re: COMBO BOX ISSUE

musefan17-Nov-09 3:19

musefan

17-Nov-09 3:19

I believe the OP asked for when the 'Form' was re-opened, not the application...

...Did you give me a 1?

Life goes very fast. Tomorrow, today is already yesterday.

Re: COMBO BOX ISSUE

EliottA17-Nov-09 3:19

EliottA

17-Nov-09 3:19

musefan wrote:
...Did you give me a 1?

Out for revenge are we?

Check out the CodeProject forum Guidelines[^]
The original soapbox 1.0 is back![^]

Re: COMBO BOX ISSUE

musefan17-Nov-09 3:23

musefan

17-Nov-09 3:23

MUST... FIND... ENEMY...

Life goes very fast. Tomorrow, today is already yesterday.

Re: COMBO BOX ISSUE

Shameel17-Nov-09 3:34

Shameel

17-Nov-09 3:34

While your answer is 'technically' correct, it is not holistic. So what if he/she wishes to persist data between different runs of the application (which is what is required for real-world apps). I don't remember giving you a 1. I don't usually do that.

Re: COMBO BOX ISSUE

musefan17-Nov-09 3:45

musefan

17-Nov-09 3:45

Like I said, there was no mention of when the application is closed and re-opened.

Also, there are valid requirements to keep the information only while the application is running. Again, there is no mention of why the functionality is required.

Life goes very fast. Tomorrow, today is already yesterday.

Re: COMBO BOX ISSUE

jashimu17-Nov-09 3:45

jashimu

17-Nov-09 3:45

Catching fish for someone is not a real help but teaching how to catch fish is a real help because you never have to catch fish for the same person again.
Teach always with good manners because inappropriate manners do not motivate anyone to learn from him/her, even if something is important to learn.

Re: COMBO BOX ISSUE

Shameel17-Nov-09 7:49

Shameel

17-Nov-09 7:49

Was my answer not mannered in some way ? I prefer fishing for them rather than teaching them to fish at least till they know what a fish is Smile | :)

HowTo Avoid Flicker

Zaegra17-Nov-09 2:12

Zaegra

17-Nov-09 2:12

Heya,

I have the following code that stretches a control to its parent size in a given number of steps. However, the panel1.update() method causes the screen to flicker. Is there a workaround for this, so that the animation will run smooth?

public void Animate(Control Ctrl, int Steps)
        {
            Bitmap OriginalView = new Bitmap(Ctrl.Width, Ctrl.Height);
            Ctrl.DrawToBitmap(OriginalView, new Rectangle(0,0,Ctrl.Width,Ctrl.Height));
            int ParentWidth = (int)Ctrl.Parent.Width;
            int ParentHeight = (int)Ctrl.Parent.Height;
            int wGrowth = (int)(ParentWidth - Ctrl.Width)/Steps;
            int hGrowth = (int) (ParentHeight - Ctrl.Height)/Steps;
            panel1.BackgroundImage = OriginalView;
            Ctrl.Visible = false;

            for (int i = 0; i < Steps; i++)
            {
                Bitmap NewRender = new Bitmap(OriginalView, new Size(OriginalView.Size.Width + i*wGrowth, OriginalView.Size.Height + i*hGrowth));
                panel1.BackgroundImage = NewRender;
                panel1.Update(); 
            }
            GC.Collect();
            Ctrl.Visible = true;
            panel1.BackgroundImage = null;
            panel1.Update();
            

        }

Thanks in advance,
Zaegra

Motivation is the key to software development.

Re: HowTo Avoid Flicker

Shameel17-Nov-09 2:36

Shameel

17-Nov-09 2:36

Enable Double Buffering on the control.

Re: HowTo Avoid Flicker

musefan17-Nov-09 3:00

musefan

17-Nov-09 3:00

What is the point of the for loop, there is no pause in between updates, thus you will get little visual effect from it. This will likely be one reason for your flickering too.

I would suggest using a timer (of some sort) and use the paint event of the panel to do your drawing.

That way you can calculate any resize values when you start the animation, and apply the values with each tick of the timer along with a call to panel.Invalidate();

Life goes very fast. Tomorrow, today is already yesterday.

Re: HowTo Avoid Flicker

Shameel17-Nov-09 3:37

Shameel

17-Nov-09 3:37

Instead of visible = false/visible = true, use BeginUpdate() and EndUpdate() methods.

Re: HowTo Avoid Flicker

ely_bob18-Nov-09 11:31

ely_bob

18-Nov-09 11:31

the biggest issue I see is the panel.BackgroundImage = null;
delete that...

what you are getting by setting the null is :

image
no image
image
no image

hence the flicker.

all you need to do is change the image. when you do, it will throw the Paint command automatically(if memory serves if not throw it manually).

What I usually do(manual double buffering)

bitmap bmp0,bmp1;

control.Image = bmp0;
bmp1 = bmp0;
(modify bmp1}
bmp0 = bmp1;
control.Image = bmp0;

no flicker!

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