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Multiple Subsequent "Main" Forms in C# Apps

, 22 Nov 2011 CPOL
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A useful technique that could be used for winform apps which require a login dialog.
In this Quick Answer question[^], aspdotnetdev recommended to the original poster to run Application.Run twice. I had never thought of doing that before, but I actually found a reason to do so in my own development process (aspdotnet gave me divine dispensation to post a tip/trick about it, but I needed a real-world example before I could do it - here's that example).
We have an application that requires the user to login. My solution was based on this little info gem.
First, I created a login form. In the form I placed the requisite userID/password textboxes, and a Login and Cancel buttons. The handlers for these buttons set the DialogResult property of the form (Login sets it to DialogResult.OK and Cancel sets it to DialogResult.Cancel).
Then, in program.cs, I have the following code:
static class Program
    private static FormSplash m_formSplash = null; 
    static void Main()
        m_formSplash = new FormSplash();
        if (m_formSplash.DialogResult == DialogResult.OK)
            Application.Run(new FormMain());
What happens is that the splash form runs, and when it exits, the application class itself determines whether or not to exit the app or run the next form.
This sure beats running the main form and having special processing in that form to handle the login form. It's A LOT cleaner (code abstraction/separation is almost always a good thing), and easier to maintain, especially if there are copious comments in the Form classes to notify the maintenance programmer (or remind the original programmer) what's happening, and why.


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


About the Author

John Simmons / outlaw programmer
Software Developer (Senior)
United States United States
I've been paid as a programmer since 1982 with experience in Pascal, and C++ (both self-taught), and began writing Windows programs in 1991 using Visual C++ and MFC. In the 2nd half of 2007, I started writing C# Windows Forms and ASP.Net applications, and have since done WPF, Silverlight, WCF, web services, and Windows services.
My weakest point is that my moments of clarity are too brief to hold a meaningful conversation that requires more than 30 seconds to complete. Thankfully, grunts of agreement are all that is required to conduct most discussions without committing to any particular belief system.

Comments and Discussions

GeneralMy vote of 5 Pinmemberkaandemirtas6-May-13 11:18 
GeneralMy vote of 5 Pinmemberj-fux19-May-12 18:56 
QuestionIs this OK? PinmembersPhinX13-Apr-12 0:35 
GeneralReason for my vote of 5 Really very nice. PinmemberAhsanS2-Feb-12 19:37 
GeneralReason for my vote of 4 I use this method in my project too Pinmemberzf.liu1-Dec-11 5:03 
GeneralReason for my vote of 5 not special, but super usefull 5 Pinmemberb1054374829-Nov-11 4:28 
GeneralThe code is using Application.Run() two times. That means tw... PinmemberAhmed Naqibul Arefin22-Nov-11 20:19 
GeneralRe: No, only one instance of the application is running. PinmvpJohn Simmons / outlaw programmer30-Nov-11 12:19 
GeneralReason for my vote of 5 Good one! Pinmembervallarasus22-Nov-11 6:49 
GeneralVery nice trick/tip. Thanks Pinmemberzenwalker19856-Nov-11 3:42 
GeneralReason for my vote of 4 always good to understand the code t... Pinmemberlxnjob10-Oct-11 6:16 
GeneralReason for my vote of 5 5 always good to understand the co... PinmemberEddy Vluggen8-Oct-11 16:37 
GeneralReason for my vote of 4 Great Example but, I would set the C... Pinmembercharles henington5-Jul-11 16:24 
GeneralVery useful and simple, thanks... PinmemberH.Johnson24-May-11 4:35 
GeneralThere is nothing special about this design of Forms applicat... PinmvpSAKryukov15-May-11 13:12 
There is nothing special about this design of Forms application.
However, there are many (mostly stupid) questions on CodeProjects Questions-and-Answer which could be resolved by just referring to this little article. My 5.
GeneralReason for my vote of 5 I really found it very usefull Pinmembersbcomputers10-Mar-11 22:26 
GeneralSuperb. PinmemberToli Cuturicu20-Dec-10 13:26 
GeneralReason for my vote of 5 Thanks, John. It does indeed work ni... PinsubeditorWalt Fair, Jr.10-Dec-10 13:55 
GeneralReason for my vote of 5 It works great. PinmemberMangore23-Jul-10 10:03 
GeneralLooks Good Pinmemberaspdotnetdev23-Jan-10 22:13 
GeneralRe: Looks Good PinmemberJohn Simmons / outlaw programmer24-Jan-10 3:14 
GeneralNice tip PinmemberAbhinav S23-Jan-10 4:49 
GeneralCould this be used to handle exceptions Pinmembersupercat922-Jan-10 8:26 
GeneralCool, but could be titled better PinmemberJ. Dunlap21-Jan-10 9:33 
GeneralRe: Cool, but could be titled better PinmemberJohn Simmons / outlaw programmer22-Jan-10 0:46 

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