Single-instance app: how to force running instance window to foreground?

[Jen]

I've implemented single-instance functionality in my .exe by using the mutex
method. Works great. But when the .exe detects that it is not the first
instance I want to bring the main window of the first instance to the
foreground and set focus to it before the .exe exits. Is this possible
using pure .NET calls or do I need Windows API calls and what are they?

[=?Utf-8?B?UGV0ZXIgUml0Y2hpZSBbQyMgTVZQXQ==?=]

There's nothing in the Framework to do what you want, you'll have to PInvoke
SetForegroundWi ndow. You can use the Process.MainWin dowHandle property with
SetForegroundWi ndow...

--
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Microsoft MVP, Visual Developer - Visual C#
"Jen" wrote:

I've implemented single-instance functionality in my .exe by using the mutex
method. Works great. But when the .exe detects that it is not the first
instance I want to bring the main window of the first instance to the
foreground and set focus to it before the .exe exits. Is this possible
using pure .NET calls or do I need Windows API calls and what are they?

[Nicholas Paldino [.NET/C# MVP]]

On top of that, the original application will have to make a call
through P/Invoke to the AllowSetForegro undWindow function to allow itself to
be brought to the front.
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard. caspershouse.co m

"Peter Ritchie [C# MVP]" <PR****@newsgro ups.nospamwrote in message
news:04******** *************** ***********@mic rosoft.com...

There's nothing in the Framework to do what you want, you'll have to
PInvoke
SetForegroundWi ndow. You can use the Process.MainWin dowHandle property
with
SetForegroundWi ndow...

--
Browse http://connect.microsoft.com/VisualStudio/feedback/ and vote.
http://www.peterRitchie.com/blog/
Microsoft MVP, Visual Developer - Visual C#
"Jen" wrote:

>I've implemented single-instance functionality in my .exe by using the
mutex
method. Works great. But when the .exe detects that it is not the first
instance I want to bring the main window of the first instance to the
foreground and set focus to it before the .exe exits. Is this possible
using pure .NET calls or do I need Windows API calls and what are they?

[=?Utf-8?B?UGV0ZXIgUml0Y2hpZSBbQyMgTVZQXQ==?=]

If the application calling SetForegroundWi ndow is the current foreground
process it should be able to call SetForegroundWi ndow without
AllowSetForegro undProcess being called. If the application calling
SetForegroundWi ndow isn't the foreground process (e.g. it doesn't have a
window) then yes, the other application must give permission to the specific
process via AllowSetForegro undProcess.

--
Browse http://connect.microsoft.com/VisualStudio/feedback/ and vote.
http://www.peterRitchie.com/blog/
Microsoft MVP, Visual Developer - Visual C#
"Nicholas Paldino [.NET/C# MVP]" wrote:

On top of that, the original application will have to make a call
through P/Invoke to the AllowSetForegro undWindow function to allow itself to
be brought to the front.
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard. caspershouse.co m

"Peter Ritchie [C# MVP]" <PR****@newsgro ups.nospamwrote in message
news:04******** *************** ***********@mic rosoft.com...

There's nothing in the Framework to do what you want, you'll have to
PInvoke
SetForegroundWi ndow. You can use the Process.MainWin dowHandle property
with
SetForegroundWi ndow...

--
Browse http://connect.microsoft.com/VisualStudio/feedback/ and vote.
http://www.peterRitchie.com/blog/
Microsoft MVP, Visual Developer - Visual C#
"Jen" wrote:

I've implemented single-instance functionality in my .exe by using the
mutex
method. Works great. But when the .exe detects that it is not the first
instance I want to bring the main window of the first instance to the
foreground and set focus to it before the .exe exits. Is this possible
using pure .NET calls or do I need Windows API calls and what are they?

[Nicholas Paldino [.NET/C# MVP]]

Well, if the OP is trying to prevent a second instance of his app from
starting, then in the second process, he would call SetForegroundWi ndow
before the application loop starts (which means he has no window).
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard. caspershouse.co m

"Peter Ritchie [C# MVP]" <PR****@newsgro ups.nospamwrote in message
news:76******** *************** ***********@mic rosoft.com...

If the application calling SetForegroundWi ndow is the current foreground
process it should be able to call SetForegroundWi ndow without
AllowSetForegro undProcess being called. If the application calling
SetForegroundWi ndow isn't the foreground process (e.g. it doesn't have a
window) then yes, the other application must give permission to the
specific
process via AllowSetForegro undProcess.

--
Browse http://connect.microsoft.com/VisualStudio/feedback/ and vote.
http://www.peterRitchie.com/blog/
Microsoft MVP, Visual Developer - Visual C#
"Nicholas Paldino [.NET/C# MVP]" wrote:

> On top of that, the original application will have to make a call
through P/Invoke to the AllowSetForegro undWindow function to allow itself
to
be brought to the front.
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard. caspershouse.co m

"Peter Ritchie [C# MVP]" <PR****@newsgro ups.nospamwrote in message
news:04******* *************** ************@mi crosoft.com...

There's nothing in the Framework to do what you want, you'll have to
PInvoke
SetForegroundWi ndow. You can use the Process.MainWin dowHandle property
with
SetForegroundWi ndow...

--
Browse http://connect.microsoft.com/VisualStudio/feedback/ and vote.
http://www.peterRitchie.com/blog/
Microsoft MVP, Visual Developer - Visual C#
"Jen" wrote:

I've implemented single-instance functionality in my .exe by using the
mutex
method. Works great. But when the .exe detects that it is not the
first
instance I want to bring the main window of the first instance to the
foreground and set focus to it before the .exe exits. Is this
possible
using pure .NET calls or do I need Windows API calls and what are
they?

[=?Utf-8?B?UGV0ZXIgUml0Y2hpZSBbQyMgTVZQXQ==?=]

There's actually a couple of examples of using SetForegroundWi ndow in .NET
that make no use of AllowSetForegro undWindow:
http://www.codeproject.com/vb/net/Ac...select=1101700
http://www.codeproject.com/csharp/oneProcessOnly.asp

I came up with a short example that attempts to call SetForegroundWi ndow
before the message pump starts:
[STAThread]
static void Main ( )
{
Process[] myProcesses =
Process.GetProc essesByName(Pro cess.GetCurrent Process().Proce ssName);
if(myProcesses != null && myProcesses.Len gth 1)
{
foreach (Process process in myProcesses)
{
if (process != Process.GetCurr entProcess())
{
UnsafeNativeMet hods.SetForegro undWindow(proce ss.MainWindowHa ndle);
return;
}
}
}
Application.Ena bleVisualStyles ();
Application.Set CompatibleTextR enderingDefault (false);
Application.Run (new Form1());
}

It seems to always bring up the other application (I only tried 10 times; so
"always" is subjective).

Could be my concept of "foreground process" (in that it has the foreground
window) is flawed. Or, it could be that SetForegroundWi ndow always works if
a process is attempting a call on SetForegroundWi ndow on another instance of
the same application and simply isn't documented. Definately a difference in
documentation though (at least my interpretation of it)...

--
Browse http://connect.microsoft.com/VisualStudio/feedback/ and vote.
http://www.peterRitchie.com/blog/
Microsoft MVP, Visual Developer - Visual C#
"Nicholas Paldino [.NET/C# MVP]" wrote:

Well, if the OP is trying to prevent a second instance of his app from
starting, then in the second process, he would call SetForegroundWi ndow
before the application loop starts (which means he has no window).
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard. caspershouse.co m

"Peter Ritchie [C# MVP]" <PR****@newsgro ups.nospamwrote in message
news:76******** *************** ***********@mic rosoft.com...

If the application calling SetForegroundWi ndow is the current foreground
process it should be able to call SetForegroundWi ndow without
AllowSetForegro undProcess being called. If the application calling
SetForegroundWi ndow isn't the foreground process (e.g. it doesn't have a
window) then yes, the other application must give permission to the
specific
process via AllowSetForegro undProcess.

--
Browse http://connect.microsoft.com/VisualStudio/feedback/ and vote.
http://www.peterRitchie.com/blog/
Microsoft MVP, Visual Developer - Visual C#
"Nicholas Paldino [.NET/C# MVP]" wrote:

On top of that, the original application will have to make a call
through P/Invoke to the AllowSetForegro undWindow function to allow itself
to
be brought to the front.
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard. caspershouse.co m

"Peter Ritchie [C# MVP]" <PR****@newsgro ups.nospamwrote in message
news:04******** *************** ***********@mic rosoft.com...
There's nothing in the Framework to do what you want, you'll have to
PInvoke
SetForegroundWi ndow. You can use the Process.MainWin dowHandle property
with
SetForegroundWi ndow...

--
Browse http://connect.microsoft.com/VisualStudio/feedback/ and vote.
http://www.peterRitchie.com/blog/
Microsoft MVP, Visual Developer - Visual C#
"Jen" wrote:

I've implemented single-instance functionality in my .exe by using the
mutex
method. Works great. But when the .exe detects that it is not the
first
instance I want to bring the main window of the first instance to the
foreground and set focus to it before the .exe exits. Is this
possible
using pure .NET calls or do I need Windows API calls and what are
they?

[Peter Duniho]

On Tue, 03 Apr 2007 11:28:08 -0700, Peter Ritchie [C# MVP]
<PR****@newsgro ups.nospamwrote :

[...]
Could be my concept of "foreground process" (in that it has the
foreground window) is flawed.

That's probably the case. I'm not actually aware of any official
definition of "foreground process", though obviously there must be one for
the documentation to make any sense. However, it seems to me that
"foreground process" could easily include simply the process that was just
started when no other changes to focus has been made. After all, if the
process starting up isn't already the foreground process when it creates
its first window, it's hard to see how the rules would allow its window to
wind up the foreground window. :)

Or, it could be that SetForegroundWi ndow always works if
a process is attempting a call on SetForegroundWi ndow on another
instance of the same application and simply isn't documented.

It would be easy enough to test for that condition. Just write a second
application that uses SetForegroundWi ndow on the first. If indeed there's
a special case for the process being the same application, then using a
second application will result in a failure to set the first application
as the foreground application.

If it works, then that would indicate that indeed a process can be the
foreground process without actually having a window.

Of course, all of this said, IMHO it's a bad idea _generally_ to use
SetForegroundWi ndow. There's a reason that the rules are complex and
there are many ways for it to not work. That is, it's rude to the user to
bring a new process to the foreground without the user's explicit
instructions or consent.

IMHO, it's almost always better to use SetActiveWindow instead. I think
that in the situation described by the OP the SetForegroundWi ndow is more
appropriate, but I hope anyone reading through this thread will note that
it's a very specific situation and the solution does not apply to all
other situations.

Pete