C# Discussion Boards - CodeProject

6-Feb-09 23:17

F2 lets you rename a file. If you need to convert between formats, then you need to read up on the formats and write a converter.

Christian Graus

Driven to the arms of OSX by Vista.

Separate thread

Muammar©6-Feb-09 19:58

Muammar©

6-Feb-09 19:58

Hi everyone,
I know this's a lame question but what is the shortest way to modify a control in a separate thread without raising the cross-thread exception..

I basically have this datagrid control and when changing its databinding properties, it's binding fine except it doesn't show it correctly.

Please help guys!

All generalizations are wrong, including this one!
(\ /)
(O.o)
(><)

Christian Graus6-Feb-09 23:16

6-Feb-09 23:16

you can turn off the cross thread exception if you want to. That's the quickest way to do it.

Christian Graus

Driven to the arms of OSX by Vista.

Muammar©6-Feb-09 23:52

Muammar©

6-Feb-09 23:52

Yeah... How about slowing down a bit Blush | :O

All generalizations are wrong, including this one!
(\ /)
(O.o)
(><)

Luc Pattyn7-Feb-09 6:46

Luc Pattyn

7-Feb-09 6:46

Christian Graus wrote:
you can turn off the cross thread exception if you want to. That's the quickest way to do it

it also is the quickest way to a disaster. I never understood why MS introduced this property,
I see no use for it whatsoever. The use of InvokeRequired/Invoke, either explicit or hidden as in BackgroundWorker events, is mandatory.

Smile | :)

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modified on Friday, June 10, 2011 11:29 PM

Daniel Grunwald7-Feb-09 0:55

Daniel Grunwald

7-Feb-09 0:55

Usually, I'm using BeginInvoke with an anonymous method:

string newValue = ...;
BeginInvoke(new Action(delegate {
   theControl.Property = newValue;
}));

You have to be a bit careful with BeginInvoke as it's always an asynchronous call; when called from the GUI thread it will delay executing the delegate until your code returns to the message loop. And you have to be careful what variables you use in the delegate - e.g. if you use a loop variable, it might have changed to the value for the next iteration before BeginInvoke calls your delegate.
But BeginInvoke is faster than Invoke because it doesn't have to wait, and it doesn't have the potential for deadlocks.

Adding a static event handler to a form that will be disposed.

Muammar©7-Feb-09 3:09

Muammar©

7-Feb-09 3:09

Hey, thanks Daniel!! That was short and very helpful!
Thanks again mate!

All generalizations are wrong, including this one!
(\ /)
(O.o)
(><)

Flyboy766-Feb-09 15:07

Flyboy76

6-Feb-09 15:07

I thought it would be possible to add a static event handler and attach to it from outside the form code add the event listener then instantiate the form with Application.Run(new Form()).

Inside the Form, the Event gets fired, and then calls Form.Close(), Application.Exit() on the Sender object (the Form) but I get an error that I cannot access an Disposed object.

I thought this would be possible if the EventHandler was static I thought it would not care if the object was disposed.

Thanks for any help guys sorry I am a newbie to UI programming.

Re: Adding a static event handler to a form that will be disposed.

N a v a n e e t h6-Feb-09 16:21

N a v a n e e t h

6-Feb-09 16:21

Not sure I got your question. Please post relevant code so that we understand what you are saying.

Smile | :)

Navaneeth

How to use google | Ask smart questions

Re: Adding a static event handler to a form that will be disposed.

Flyboy767-Feb-09 17:35

Flyboy76

7-Feb-09 17:35

Thanks Navaneeth,

Here is an example of what I am trying to do:

// Entry Point:

DummyForm.TestsFinished += new EventHandler(DummyForm_TestsFinished);

// Start Processing the query
// viewFrameworkDummyForm.ProcessQueryInstructions(queryInstructions);

// Start the Application message pump (the viewFx has to be run on a form to be contained within a thread UI)
DummyForm myForm;

// ****************************************
// I get a Cannot access disposed object ex on this below line:
// ****************************************

Application.Run(myForm = new DummyForm(queryInstructions));

// DummyForm:

public partial class ViewFrameworkDummyForm : Form
{
private List&lt;QueryInstruction&gt; queryInstructions;
public static event EventHandler TestsFinished;

/// <summary>
/// Constructor
/// <summary>
void DummyForm(List<QueryInstructions>queryInstructions)
{

…

// Does stuff with query instructions…

…

// Event gets fired somewhere in the constructor…
OnQueryInstructionsProcessed(this,new EventArgs());

…
}

// Notifies the attached events to QueryInstructionsProcessed, that the query instructions have been processed.
void OnQueryInstructionsProcessed(object sender, EventArgs e)
{
//Inform that the tests have been finished, and then close the form..
TestsFinished(this, new EventArgs());
this.Close();
Application.Exit();
}
}

Reading multiple records from a database

ferronrsmith6-Feb-09 13:56

6-Feb-09 13:56

i wanna pull multiple records in from a database and display them in different labels

I was thinking of returning them in an array then adding them to the specified labels, can anyone point me to the an example or aid me.

sample code

public partial class _Default : System.Web.UI.Page
{
SqlConnection con = new SqlConnection("server=BABOO;uid=sa;password=sa;database=quiz");
protected void Page_Load(object sender, EventArgs e)
{
con.Open();
string query;
query = "select QuestionText,AnswerA,AnswerB,AnswerC,AnswerD from quest where QuestionID='1'";
SqlCommand cmd = new SqlCommand(query, con);
SqlDataReader dr;
dr = cmd.ExecuteReader();
while (dr.Read())
{
nt rbCount = Convert.ToInt32(TextBox2.Text);
//iin textbox enter how many record want to display
RadioButton[] radioButtons = new RadioButton[rbCount];
for (int i = 0; i < rbCount; ++i)
{
radioButtons[i] = new RadioButton();

radioButtons[i].Text = dr.GetValue(1).ToString();
}

Please i need your help

Ferron

Christian Graus6-Feb-09 14:08

6-Feb-09 14:08

So, this seems a little retarded to me.

1 - you want to have a textbox showing how many answers to show ? So, what if the right answer gets hidden ?
2 - how do you make sure that textbox2 contains a number ?
3 - why don't your variables have real names ?
4 - You're reading the same value from the answer list every time
5 - you never add the radio buttons to your UI

Christian Graus

Driven to the arms of OSX by Vista.

ferronrsmith6-Feb-09 14:19

6-Feb-09 14:19

i know, that's why i need your help to sort it out the write way. basically what i have is 3 textbox

text[1]
text[2]
text[3]

if three records are in the database it should bring back three sets of record all in their respective textbox.

Plz can u help

Ferron

Christian Graus6-Feb-09 16:31

6-Feb-09 16:31

So the possible answers go in textboxes, not in radio buttons ?

Are you saying the number of answers is flexible ? I would do this with a data bound control, assuming I had to show more than one question on a page.

Christian Graus

Driven to the arms of OSX by Vista.

ferronrsmith6-Feb-09 16:48

6-Feb-09 16:48

Yes I want to show the results in the text box? I have it created in a form. Is the the data bound control flexible? Can the realit be formatted in a form like manner, for say a application form?

Ferron

Christian Graus6-Feb-09 18:16

6-Feb-09 18:16

Yeah, you can define a template for a data bound control and show the data any way you like.

Christian Graus

Driven to the arms of OSX by Vista.

ferronrsmith6-Feb-09 20:22