string variable - C# Discussion Boards

Show Form from (non-GUI) Thread

28-Aug-06 7:34

Hello

I don't know, but!! I guess your question is already self answering.

You've changed the filter of the DataTable indexed zero. You have to populate the view with that new filter.

That's is dont by either assigning to the DataSource property because it populates the records of the table through the already filtered view, or by using DataViewManager.CreateDataView() method

If someone knows otherwise, please post!

Regards

LiamD28-Aug-06 5:44

LiamD

28-Aug-06 5:44

I have a thread (which is not the main GUI thread )that I want to be able to create a form using the Show method.

The thread basically loops for commands and responds to them. Some of the commands are to display a form - and then wait for the next command.

Now when I try to do this the Form freezes i.e. not responding. Now I assume that is because the thread is blocking waiting (Monitor.Wait) for the next command. I suppose this blocking prevent the GUI from responding to events.

So my question is related to this problem.

1. Is is good practice to create Form from a thread other than the main GUI
2. Can I do a for.Show method and spawn it into a worker thread?

All thoughts and suggestions would be appreciated.

Re: Show Form from (non-GUI) Thread

Nader Elshehabi28-Aug-06 7:10

Re: Show Form from (non-GUI) Thread

28-Aug-06 7:10

Hello

LiamD wrote:
Is is good practice to create Form from a thread other than the main GUI

If you want your working thread to be blocked by the shown forms, you can use it to show these forms. Simple, isn't it?? Smile | :)

OTOH I don't think is what you want. So, simply make a thread for each form that is shown. The thread should be alive as long as the form is visible. Once the form is closed, abort the thread nd dispose it.
And yes of course!! Sometimes this is a good practice, depending on the structure of your program.

LiamD wrote:
Can I do a for.Show method and spawn it into a worker thread?

I don't know what is a "for.Show" method, but you can -and probably should- show each form on its own thread as above.

Regards

LiamD28-Aug-06 8:59

LiamD

28-Aug-06 8:59

I was concerned because i have never seen any examples of projects creating a thread for each form.

Can you please give an example of code for this? Something liek this ...

Form f = new Form();
t = new Thread(new ThreadStart(f));
t.Start();

I just want to make sure that I will not run into problem using this method when running in a multi threaded project.

By the way I meant to write Form.Show() method above.

Thanks,
Liam

Re: Show Form from (non-GUI) Thread

Nader Elshehabi28-Aug-06 9:51

28-Aug-06 9:51

Hello

Well, running into trouble in multithreading is as easy as slipping in the mud in a rainy day!! There are two scenarios. One if you want to keep track of each thread -for several reasons I suppose-. This is the hard way, so I'd rather skip it for now Big Grin | :-D

.
The easy way is to launch each thread and let it die as it finishes without tracking -Thank God for the GarbageCollector!!-. Here is a sample code:

private void button2_PreviewKeyDown(object sender, PreviewKeyDownEventArgs e)
{
    Thread MyThread = new Thread(new ThreadStart(MyThreadMethod));
    MyThread.Start();
}

private void MyThreadMethod()
{
    Form1 MyForm = new Form1();
    MyForm.ShowDialog();//To Block the thread excution
}

The Thread will die and get collected once the form is closed. Carful not to open too many forms though.

Regards

string variable

TAREQ F ABUZUHRI28-Aug-06 5:25

TAREQ F ABUZUHRI

28-Aug-06 5:25

in my program i diclar

string itm1,itm2,itm3,itm4,itm5,itm6,itm7,itm8,itm9,itm10,itm11,itm12,itm13;

i want to make method as

save(int ID,string Value)
{
itm+ID=Value;
//itm1=value;
}

the problem now in this line ([itm+ID=Value;])
i cant make this
but how cam make thing like this

?????????????????

Palestine

Andrei Ungureanu28-Aug-06 5:30

Andrei Ungureanu

28-Aug-06 5:30

Hi,
Try using an array. Like this:

<br />
string []items = new string[13];<br />

And then create the function:

<br />
public string Save(int index,string Value)<br />
{<br />
  items[index] = Value;<br />
}<br />

Do your best to be the best

Judah Gabriel Himango28-Aug-06 5:31

Judah Gabriel Himango

28-Aug-06 5:31

TAREQ F ABUZUHRI wrote:
string itm1,itm2,itm3,itm4,itm5,itm6,itm7,itm8,itm9,itm10,itm11,itm12,itm13;

i want to make method as

save(int ID,string Value)
{
itm+ID=Value;
//itm1=value;
}

That won't work, Tareq. And it's bad design too, don't do that. Instead, use a string[]:

string[] items = new string[13];

...

save(int ID, string Value)
{
   items[ID] = Value;
}

Tech, life, family, faith: Give me a visit.
I'm currently blogging about: Dumbest. Movie. Title. Evaaar.
The apostle Paul, modernly speaking: Epistles of Paul

Judah Himango

*edit* oops, karkster beat me to it.

Nader Elshehabi28-Aug-06 5:35

28-Aug-06 5:35

Hello

Put your items in an array and access them using the index.

string MyItems[] = new string[13];

public void Save(int ID, string Value)
{
    MyItems[ID] = Value;
}

Regards

Re: string variable [modified]

Martin#28-Aug-06 7:25

Martin#

28-Aug-06 7:25

Hello,

if you whant to make it dynamic some day, you should use "System.Collection.Specialized.StringCollection"

All the best,

Martin

eggsovereasy28-Aug-06 8:40

eggsovereasy

28-Aug-06 8:40

Even better than an array of strings!

private dictionary<int, string> items = new dictionary<int, string>();

public void save (int id, string value)
{
  items[id] = value;
}

-- modified at 14:41 Monday 28th August, 2006

Maybe I should clarify why its better... your "id"s need only be unique with a dictionary, whereas with the string array they would need to be, unique and sequential. Also stuck in a certain range (unless you used an offset).

How do I initialize the checkbox column?

printscreen1234528-Aug-06 5:18

28-Aug-06 5:18

I have inserted a datagridviewcheckboxcolumn. But the values of those the checkbox cells are all set to null by default. How do I change them all to "false" which is unchecked?

Nader Elshehabi28-Aug-06 5:51

28-Aug-06 5:51

Hello

Is your DataGridView databound?? In this case you could just use this line of code to return false to the datasource when the user leaves the value null:

dataGridView1.Columns[0].DefaultCellStyle.DataSourceNullValue = false;

If you still want to initialize the values of the cells, I remember something about default values in DatagridView, but i don't seem to recall it at the moment..

What I can think of now is to handle the RowsAdded and initialize the new cells value to false.

Regards

printscreen1234528-Aug-06 15:03

28-Aug-06 15:03

Hi
I have set the datagridview.datasource to the defaultview of a datatable. Is it databound then? The thing is that the checkbox column is inserted to the datagridview with null values by default.

The idea is to let the user to check for export. Cos the unchecked boxes are of null values, I've got an error when the null value is accessed.

Nader Elshehabi28-Aug-06 19:24

28-Aug-06 19:24

Hello

I provided you with two possible solutions in my last post. Are they not suitable??

1- You could ignore the null value and return false to the datasource. This should eleminate the error:

dataGridView1.Columns[0].DefaultCellStyle.DataSourceNullValue = false;

2-Otherwise you could handle the RowsAdded event and set the value of your column for each new row to false

Regards

printscreen1234529-Aug-06 1:38

29-Aug-06 1:38

Hi
I've tried both but they don't seem to work. It could be that the datagridview is not databound??? For the 2nd solution, it seemed to work initially, but I don't know why the value switched back to null again. I have made the datagridview a global variable, so nothing should have changed the value back.

Now I don't know what to do.

Nader Elshehabi29-Aug-06 2:32

29-Aug-06 2:32

Hello

printscreen12345 wrote:
I don't know why the value switched back to null again.

What??!!

What do you mean switched back again?!! Are you sure you did initialize them to false??

Also, how do you populate your DataGridView if it's not databound?

Regards

printscreen1234529-Aug-06 2:41

29-Aug-06 2:41

Hi
Yes, I did initialise them to false in the "try" block and they switched back to null in the "finally" block.

I'm not sure if the DataGridView is databound or not. As mentioned in my earlier messsage, I have set dataGridView1.DataSource to a defaultView of a datatable. Is this databound??

Nader Elshehabi29-Aug-06 5:16

Re: How do I initialize the checkbox column? [modified]

29-Aug-06 5:16

Hello

Yes this is databound, as long as your DataGridView is populated automatically via the view.

now let's work this out step by step..

1-Does your try throws an exception?? I mean do you catch anything in the catch block??
2- After you change the value to false, make a break point and watch the value of the last row to be changed.

Regards

printscreen1234529-Aug-06 14:55

29-Aug-06 14:55

Hi,

There is no exception thrown at all. It goes straight into the finally block from the last line of code in the try block.

I set a break point at the last line of code in the try block and watched the value of the 1st 10 rows of the checkboxcolumn. They were all set to false. But when it stepped into the next line of code (which is the "}" of the try block), they all turned back to null value. This means, it is at the end of the try block that they were switched back.

I just realised one thing. The datagridview is displayed when I press a search button. It is very strange that the false values are all switched back to null only the first time when the search button is pressed. They all remained set to false the second time onwards. Actually it has the same kind of problem with the row numbers display - it will never display the row numbers for the first time but it will from the 2nd time onward. Strange?!!

Thanks

-- modified at 21:12 Tuesday 29th August, 2006

Nader Elshehabi30-Aug-06 7:56