Multiple Sub Form Opening

Question

2.50/5 (2 votes)

See more:

Hi
In my Program.cs the code is :

C#

bool createdNew;
m_Mutex = new Mutex(true, "App", out createdNew);
if (createdNew)
     Application.Run(new StartForm());
else
     MessageBox.Show("The application is already running.", Application.ProductName,
                  MessageBoxButtons.OK, MessageBoxIcon.Exclamation);

In my StartForm.cs after InitializeComponent the code is :

C#

Form1 f1 = new Form1();
f1.Visible = false;
f1.ShowDialog(this);

My requirement here is :
when I double the application exe when an instance is already running, instead of just displaying "Application is running" I want to check if Form1 is already open.
1. If Form1 is already open do nothing.
2. If Form1 not open showdialog Form1 from StartForm.cs

Please note that StartForm always stays in systray

Thanks in advance

Posted 18-Dec-14 9:36am

tvks

Updated 18-Dec-14 9:40am

v2

Add a Solution

Comments

Sergey Alexandrovich Kryukov 18-Dec-14 16:17pm

Not a question. There is no such concept as "sub form". What are you trying to achieve? Why using that mutex? Do you want to use it as the indication of first application instance running? What's the problem?
—SA

BillWoodruff 19-Dec-14 4:10am

Please clarify: do you want the Application to terminate when all Forms are closed ?

It is possible to have a WinForms app where all Forms can be closed, and the Application is still running: of course, you must have way to interact with the Application when all the Forms are closed: that is usually done by having a SystemTray Notification Icon.

2 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Sergey Alexandrovich Kryukov · Answer 1 · 2014-12-18T10:20:00

Solution 1

If you are trying to implement single-instance application behavior, my past answers can help you:
Enter multiple commands to only one process instance[^],
Custom Windows right-click command launching multiple instances[^].

Your follow-up questions will be welcome.

—SA

Posted 18-Dec-14 10:20am

Sergey Alexandrovich Kryukov

Comments

Maciej Los 18-Dec-14 17:22pm

Sounds... great!
+5!

Sergey Alexandrovich Kryukov 18-Dec-14 17:51pm

Thank you, Maciej.
—SA

[no name] 18-Dec-14 17:41pm

Yep also my 5. But also the boring "Bruno" question again "how to solve this" over session boundaries.

Sergey Alexandrovich Kryukov 18-Dec-14 17:52pm

Thank you, Bruno.
So, what's up with session boundaries? Could you explain the problem?
—SA

BillWoodruff · Answer 2 · 2014-12-18T20:14:00

First, the implication (that I read) in your post that there could be your App running without a Form instance created (so the "Message Pump" of the Application does not depend upon a Form) suggests a Windows Service might be the right choice of App structure for you. Just ignore this comment if I incorrectly interpret your post.

Second, the question of how to make a single-instance WinForms App is one many people have addressed:

1. Scott Hanselman presented a solution in 2008 using the Visual Basic Library in C#: [^].

2. To use the Mutex ... which is, evidently, on your mind ... see the CodeProject article: "Single Instance Form Application in C#" December 2013: [^].

By far the best example, and discussion, of the use of Mutex for a single-instance app I have seen is in Mark Michaelis' "Essential C# 4.0," Chapter 19.8. The sample code for that book can be downloaded (.pdf) here: [^], and you will find his sample code in the Chapter 19 folder.

3. Chris Sells in his 2006 book on C# WinForms (Chapter 14) covers several interesting alternative ways to run a WinForms Application: [^].

Chapter 14 is available as a free download (.pdf) here: [^].

Note that this chapter does not cover creating a single-instance application; for that, Sells, like Hanselman, uses the Visual Basic Library, and that is covered in another chapter.