Question

I’ve two nested Forms (form1 and form2) showed modally, i.e. from my MainForm I show the form1 modally by calling (on a button click event) form1.ShowDialog() and from the code of form1 I then call (on another button click event) form2.ShowDialog().

By setting the DialogResult property of the form2 (e.g. by clicking the X close button on the form title bar), the form2 is hidden (as expected) but also the form1 is hidden (unexpectedly). The main thread executes the code after the form2.ShowDialog() line and, immediately after, keeps on executing the code after the form1.ShowDialog() line.

I tried out the same nested pattern with a new project and it came out that the hiding is not propagated to the first calling form. Hence there must be something wrong with my code, but I cannot find it. Anyone knows what could cause this?

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If this can help, I’ve also stopped both projects in debug mode immediately after clicking the close button of the form2. The Call Stacks of both projects are exactly the same from the call to the Program.Main() on. The Call Stacks only differ before this call. I try to highlight the differences:

Not working project

[Native to Managed Transition]  
[Managed to Native Transition]  
mscorlib.dll!System.AppDomain.nExecuteAssembly(System.Reflection.RuntimeAssembly assembly, string[] args) + 0x9 bytes   
mscorlib.dll!System.Runtime.Hosting.ManifestRunner.Run(bool checkAptModel) + 0x6e bytes 
mscorlib.dll!System.Runtime.Hosting.ManifestRunner.ExecuteAsAssembly() + 0x90 bytes 
mscorlib.dll!System.Runtime.Hosting.ApplicationActivator.CreateInstance(System.ActivationContext activationContext, string[] activationCustomData) + 0x65 bytes 
mscorlib.dll!System.Runtime.Hosting.ApplicationActivator.CreateInstance(System.ActivationContext activationContext) + 0xd bytes 
mscorlib.dll!System.Activator.CreateInstance(System.ActivationContext activationContext) + 0x44 bytes   
Microsoft.VisualStudio.HostingProcess.Utilities.dll!Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssemblyDebugInZone() + 0x23 bytes
mscorlib.dll!System.Threading.ThreadHelper.ThreadStart_Context(object state) + 0x63 bytes   
mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool ignoreSyncCtx) + 0xb0 bytes    
mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state) + 0x2c bytes    
mscorlib.dll!System.Threading.ThreadHelper.ThreadStart() + 0x44 bytes   
[Native to Managed Transition]

Working project

[Native to Managed Transition]  
[Managed to Native Transition]  
mscorlib.dll!System.AppDomain.ExecuteAssembly(string assemblyFile, System.Security.Policy.Evidence assemblySecurity, string[] args) + 0x6d bytes    
Microsoft.VisualStudio.HostingProcess.Utilities.dll!Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly() + 0x2a bytes  
mscorlib.dll!System.Threading.ThreadHelper.ThreadStart_Context(object state) + 0x63 bytes   
mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool ignoreSyncCtx) + 0xb0 bytes    
mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state) + 0x2c bytes    
mscorlib.dll!System.Threading.ThreadHelper.ThreadStart() + 0x44 bytes   
    [Native to Managed Transition]

EDIT
Here instead is how I open the forms:

private void button1_Click(object sender, EventArgs e)
{
    using (Form2 form2 = new Form2())
    {
        form2.ShowDialog();
    }
}

Answer 1

I would imagine that the button1 control on Form1 has the DialogResult property set to something other than DialogResult.None.