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Having trawled t'internet for the answer to the following question, it seems that a lot of people have asked this over the years; here's the issue:-

I have my library working away just fine. I would now like to launch a UI so that someone can simulate some function or other, introduce errors, change variables etc...

So, I have my form

C#

Form1 simUi;

and iv'e tried creating this in a method which is

C#

[STAThread]

(seems to be t'internets favourite answer)

C#

simUi = new Form1();

Now, here's the problem: If I use

C#

simUi.ShowDialog();

The method never returns; at least until I close the form. Whereas, if I use

C#

simUi.Show();

It returns but doesn't finish rendering the form and so is equally useless.
I want to be able to start the "ShowDialogue" in it's own thread but the compiler complains that the return type is incorrect.
So, how is best to do this ? Note that I have a number of controls on my form and so I don't just want to update a dialoge box. The plan is to use the properties in my form1.cs to access the responces on my UI and update any value's; I have a timer event to refresh.

Hopefully I am overlooking something that is obvious to all of you gurus'

Thanks Richard,
When I call the Show() method, the window appears but with no controls or buttons; just a blank grey box.

@Lukeer

C#

guiThread = new System.Threading.Thread(new System.Threading.ThreadStart(simUi.ShowDialog));

guiThread.Start();

UPDATE:
Perhaps I need to elaborate a bit more:- My project is essentially an instrument class driver ; depending on which instrument is connected, it picks the correct driver to use and begins it’s work in it’s own thread. There wouldn’t ordinarily be any need for a UI but this dll is now being used by other people and teams. I had included a “simulation” feature to enable my development whilst not attached to any hardware but this was/is relatively simplistic. My internal “customers” are developing in the same way using my simulator but would like to invoke every error condition / state possible; this requires me to add a human interface. I know this is possible because I have seen similar done before.
So, if I could just find a way of running the ShowDialogue() in it’s won thread or getting the Show() to draw the controls, I’d have it licked…

Posted 7-Jun-13 0:08am

Member 9862872

Updated 7-Jun-13 4:25am

v4

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lukeer 7-Jun-13 8:05am

Show the code you used to create the UI on a separate thread.
Mark where the return type error occured.

lukeer 7-Jun-13 9:20am

I can explain why you're getting an error: You try to create a new instance of System.Threading.ThreadStart. As parameter you use simUi.ShowDialog. This method has the signature public DialogResult MethodName(). But the constructor you use expects a signature of public void MethodName(). That's why the compiler complains about the return type. It's void vs DialogResult.

I have no immediate solution except for saying that in a "normal" Windows Forms application, the UI thread is the main thread and starts the main form like this:


Application.Run(YourMainFormInstance);

That's a blocking call. So you usually put everything else in a separate thread instead of putting the UI in a separate thread.

Hope that helps somehow.

PS: If you want me to get automatically informed of something you wrote, reply to something that I wrote. Or add the important information to your question, like you did, and then leave me a small comment saying that you did so (You can Reply to this comment).

Member 9862872 7-Jun-13 9:43am

Thanks Lukeer, Yes, this would be a non-issue if it was a Windows Forms Application but unfortunately this isn't possible in this instance.

2 solutions

Solution 1

The ShowDialog() method never returns, because it is a dialog. It's purpose is to allow the user to enter information in the various controls, and then signify completion by pressing the "OK" button (or similar). By contrast the Show() method offers a fully interactive window that does not require a "completion" indicator, it usually closes when the application is terminated.

However, I cannot see any obvious problem from your description; I think you need to edit your question and provide a bit more detail.

Posted 7-Jun-13 1:25am

Richard MacCutchan

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lukeer · Accepted Answer · 2013-06-09T22:23:00

This one works for me:

C#

using System;
using System.Collections.Generic;
using System.Text;

namespace KillmeConsole
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("And now, starting a window...");


            System.Threading.ThreadStart ts = new System.Threading.ThreadStart(ShowForm);
            System.Threading.Thread uiThread = new System.Threading.Thread(ts);
            uiThread.Start();
            


            Console.WriteLine("Did it happen?");
        }


        private static void ShowForm()
        {
            System.Windows.Forms.Application.Run(new MainForm());
        }
    }

    public class MainForm : System.Windows.Forms.Form
    {
        System.Windows.Forms.Button btNix = new System.Windows.Forms.Button();

        public MainForm()
        {
            btNix.Location = new System.Drawing.Point(20, 20);
            btNix.Name = "btNix";
            btNix.Text = "Nix";
            this.Controls.Add(btNix);
        }
    }
}

There's just ShowForm(), a void-returning method without parameters. As such it matches what ThreadStart's constructor expects. It then runs the application window. It is still a blocking call, but since the method itself runs on a separate thread (uiThread), the main program can continue.

The application doesn't exit before the UI thread exits (just close the window).

This one needs references added to System.Windows.Forms.dll and System.Drawing.