showing form from thread

Sunshine Always

Hi In my application, the Main form starts a thread in another class. In this thread I need to show another form as modeless. If i call it in the thread, the form shows but in a hanged state. no controls are visible and it is in not responding state. How can i achieve my requirement. Please help. Thanks.

wasifmuneer

Did you use BackgroundWorkerClass???

Sunshine Always

No. It is a normal class whose object i'm using in mainform

Luc Pattyn

Hi, this article[^] deals with Controls and Threads. :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

I only read formatted code with indentation, so please use PRE tags for code snippets.

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The Man from U N C L E

You have to create all your forms on the GUI thread, of which there can only be one in the application. I suggest you invoke a method back onto the Main Form thread to create the new modeless form.

If you have knowledge, let others light their candles at it. Margaret Fuller (1810 - 1850) [My Articles] [My Website]

DaveyM69

I'm not sure about the best practices where this is concerned. It's not something I would ever do so I haven't investigated and could maybe have some disasterous consequences. A quick test however reveals it works - I'm sure others will comment!

using System;
using System.Threading;
using System.Windows.Forms;

namespace Forms_Test
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
Load += new EventHandler(Form1_Load);
}
private void Form1_Load(object sender, EventArgs e)
{
Thread thread = new Thread(new ThreadStart(StartNewThread));
thread.Start();
}
private void StartNewThread()
{
Application.Run(new Form2());
}
}
}

Edit: This MSDN[^] link may be of interest.

Dave

If this helped, please vote & accept answer!

Binging is like googling, it just feels dirtier. (Pete O'Hanlon)
BTW, in software, hope and pray is not a viable strategy. (Luc Pattyn)

realJSOP

You could post an (custom) event that the main form responds to, and let the main form create the modelss window...

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The Man from U N C L E

It works, but ugh! The main message loop that started Form1 will end when that closes, fire any application clean-up code you wrote and leave Form2 orphaned. It is a bit like firing up another application using Process.Start. Form2 would have to be treated as a separate application and the start thread must do all the usual stuff you need to run, and shut down an application. On the down side, they would reside in the same AppDomain and a crash in either thread would then kill both, also communication between the parts would be a nightmare. I'm not sure how they manage it, but I guess Office does something similar for Word and Excel etc. where it appears to fire up a new instance of Word for each document, and they can be closed independently, however only one process is running. Interestingly in the browser world things are moving the other way, eg. Google Chrome runs each tab in a separate Process, so you get one apparent application but multiple processes!

If you have knowledge, let others light their candles at it. Margaret Fuller (1810 - 1850) [My Articles] [My Website]

DaveyM69

Agreed - hence the caveats I placed in there. :thumbsup:

Dave

If this helped, please vote & accept answer!

Binging is like googling, it just feels dirtier. (Pete O'Hanlon)
BTW, in software, hope and pray is not a viable strategy. (Luc Pattyn)

AspDotNetDev

private void button1_Click(object sender, EventArgs e)
{
System.Threading.Thread t = new System.Threading.Thread(
new System.Threading.ThreadStart(delegate
{
Form1 frm = new Form1();
frm.ShowDialog();
}));
t.Start();
}

That seems to work for me.

[Forum Guidelines]

Dave Kreskowiak

It may work for you, but it's not going to work in all instances and environments and it WILL produce bugs that are difficult, if not impossible, to track down. The short answer is you just don't put up UI elements on anything other than the UI thread.

A guide to posting questions on CodeProject[^]
Dave Kreskowiak Microsoft MVP Visual Developer - Visual Basic
2006, 2007, 2008
But no longer in 2009...

AspDotNetDev

Dave Kreskowiak wrote:

it WILL produce bugs

You sure about that? Do you have a concrete example?

[Forum Guidelines]

Dave Kreskowiak

There's no such thing as a "concrete" example of this. All you have to do is ask around.

A guide to posting questions on CodeProject[^]
Dave Kreskowiak Microsoft MVP Visual Developer - Visual Basic
2006, 2007, 2008
But no longer in 2009...

AspDotNetDev

Word on the street, huh? Oooooo....k.

[Forum Guidelines]

Dave Kreskowiak

Ask around HERE. You want the professional experience behind it? Ask around HERE. Don't take just my word for it. Ask everyone with an MVP icon next to their name.

A guide to posting questions on CodeProject[^]
Dave Kreskowiak Microsoft MVP Visual Developer - Visual Basic
2006, 2007, 2008
But no longer in 2009...

The Man from U N C L E

Ask anyone who have ever done anything with threading. The most common bug I come across where I work is anything accessing the UI from another thread, either creating stuff, or just calling methods and properties across threads. It is worth noting that the debug environment runs in a rather safe mode (somehow) and so threading issues rarely show up during development, unless they are really bad. Worse, you cannot step through them easily as the timing of actions on different threads makes a big difference. In my experience 50% of threading issues break the application on the first time they are run in a release environment. Of the other 50% it depends on the hardware and network environment. We had a threading issue that only came to light a year after release when the end user upgraded their machine. Suddenly one of the threads ran faster (probably off on another core, or just from the faster processor) and the bug climbed out of hiding. World of pain!

If you have knowledge, let others light their candles at it. Margaret Fuller (1810 - 1850) [My Articles] [My Website]

The Man from U N C L E

Bug number 1. You used ShowDialog which should produce a modal dialog, however it is modeless, due to running on a separate thread. Therefore you can spawn hundreds of these secondary dialogs, oops. Not an execution bug in this case, but clearly a process flow bug. Having said that changing your code to Show doesn't produce any visible form at all.

If you have knowledge, let others light their candles at it. Margaret Fuller (1810 - 1850) [My Articles] [My Website]

Sunshine Always

I tried calling a delegate.BeginInvoke in the thread for the main form in which i called the new form.show. but same results. the new form is in hanged state.

The Man from U N C L E

BeginInvoke is not needed as the Show is not going to block any threads. Just call MainForm.Invoke with the delegate to show the newForm. eg.

        Thread thread = new Thread(new ThreadStart(StartNewThread));
        thread.Start();
    }

    void StartNewThread(){
        //Application.Run(new Form2());
        this.Invoke(new MethodInvoker(this.LaunchForm2));
    }	
    
    void LaunchForm2(){
		Form2 frm = new Form2();
		frm.Show();
    }

I know as a standalone example my code would be daft, why start a new thread just to invoke back to the original thread, but I assume you are doing some other processing in the secondary thread to make it worthwhile.

If you have knowledge, let others light their candles at it. Margaret Fuller (1810 - 1850) [My Articles] [My Website]