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Hi All,
I have a situation where I need to do some custom message filtering.
Unfortunately I need more functionality than provided by the
IMessageFilter system or by overriding a Form's wndproc() method.
What I need is to be able to run code before and after a message is
processed and optionally drop selected messages.
As I understand it:
The IMessageFilter system only allows filtering out selected messages
(can't run code after they have been processed)
A Form's wndproc method only sees messages destined for that form. (I
need to handle all messages for the entire application)
In an unmanaged application say in visual c++ it would be a simple
matter of implementing ones own getmessage/dispatchmessage loop. In
the dotnet framework the actual message loop is implemented in native
code and is inaccessible to the programmer.
Does anyone know a solution for this?
Regards,
Felix
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Unfortunately, the only thing you can do outside the form is use Application.AddMessageFilter to add your own filter, and (as you've surmised), this only works on capturing a message before it is dispatched to the window. What you could possibly do (and this would be one heck of a hack), is use a combination of AddMessageFilter and a Mediator to control what happens. What you'd do is hook into the WndProc of each form, and pass the details to the mediator to work out whether or not the message could be processed.
"WPF has many lovers. It's a veritable porn star!" - Josh Smith As Braveheart once said, "You can take our freedom but you'll never take our Hobnobs!" - Martin Hughes.
My blog | My articles | MoXAML PowerToys | Onyx
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Thanks for your answer. I think I may have to add a custom BaseForm class that overrides the wndproc and which all of my Forms inherit from. That way I could insert global message processing which would be similar to writing a custom message loop.
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Keep in mind existing dialogs (OpenFileDialog, MessageBox, ...) will not inherit from your BaseForm, so while one of those is open, your special message handling will not occur automatically.
Luc Pattyn [Forum Guidelines] [My Articles]
The quality and detail of your question reflects on the effectiveness of the help you are likely to get.
Show formatted code inside PRE tags, and give clear symptoms when describing a problem.
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Yeah, it is not ideal.
As there seem to be so many helpful knowledgeable people on here, I'll describe the actual problem I'm trying to solve and see if there are any other ideas.
The problem I'm having is that inside one of my event handlers I'm calling some DirectShow code. Inside the DirectShow code a message loop is run to handle the COM calls. Unfortunately this inner message loop pumps my input events so if I click quickly with the mouse I can get a second event handler running nested inside the first at the point of the DirectShow call. I'm not sure what the correct term is for this behaviour so I am calling it reentrant event processing (although it is not strictly rentrancy as the event handlers are likely to be different ones). The problem arises because all the event handler code assumes that it is single threaded (which it is) and that events will be processed in order from the queue. I get unpredictable crashes of my application due to this problem.
One solution I am looking at is to simply discard user input messages and timer messages while a message is being processed, hence the original topic of this thread.
Another more complicated but better solution is to run a second thread with it's own message loop and invoke the COM calls on that thread. I haven't looked into the details of this too much as yet.
I've got a simple project that demonstrates the problem which I can post if anyone would like to see it.
Thanks for your help!
regards,
Felix
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I've had a similar issue when I try to link controls together, like a textBox and a trackBar, where updating one control should update the other. Here's how I solved it. Keep in mind this only works if it's managed code that you're trying to keep "non-reentrant".
If your code is assuming a single-threaded environment, you could try setting a lock before the DirectShow code gets called, and check that lock at the beginning of the nested events, like so:
bool lock = false;
void SomeEvent(object sender, EventArgs e)
{
if(!lock){
lock = true;
DirectShowCall();
lock = false;
}
}
void NestedEvent(object sender, EventArgs e)
{
if(!lock)
{
}
}
The lock check in SomeEvent will prevent your DirectShow code from getting called in a nested fashion.
This method isn't thread-safe. If you need thread-safety, you may want to look at Monitor.TryEnter.[^]
Dybs
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Hi Dybs,
naturally that is a great solution if you can easily identify SomeEvent and NestedEvent, however in my case this is not so easy, there are many events that can lead to a DirectShow call and many events that could be unsafe to process nested within another call. I could search through my code and put locks in all event handlers that look likely to cause trouble but this discipline would need to be maintained in maintenance and future development, so is not ideal. The solution you propose is really a special case of my proposal to override the wndproc of all forms (by using a custom BaseForm class). The whole point of an event queue and a single gui thread is so that in programming these events one can consider them as occurring serially. Overriding message processing for the whole app will place some overhead on all activity so I'd rather avoid the wndproc solution. Another disadvantage is that by effectively discarding some messages I might see strange behaviour, for example if a user started typing while in the lock the letters entered up to the point of releasing the lock would be lost.
The alternative solution I'm going to investigate is to start a second thread with its own message loop and make all DirectShow calls synchronously on that thread. Due to good architectural choices early on in the project the references to DirectShow in my application are limited to one module so it should be easy to ensure that all calls are routed through the second thread. If it works I'll post an article here to explain the solution.
Regards,
Felix
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Hi, guys
I use NATUPNPLib in order to allow my application to be reachable from Internet, although it is running on machine behind router (IGD). So I use this library to add port mapping/forwarding. But now I am kind of confused and I need help.
My first question is which IP to add in the mapping table for "local"? I've got several IPs returned by Dns.GetHostEntry(Dns.GetHostName()) for my machine, because I've got several network adapters. And I don't know which one to use for port mapping. If there is any records in the mapping table, I could examine an existing local IP from the table and I could compare it to my IPs to choose one of them. But what should I do when there aren't records?
My second question is, hypothetically, what will happen if there are more than one routers which the machine is connected to (through different adapters)? Which router will NATUPNPLib represent? Maybe all together? And in this scenario (several routers, each one connected to Internet) which adapter/router will Windows use to connect to Internet?
Best regards
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Well, you're either going to have to write code to determine the best path to the router you want (not exactly easy), or better yet, make your app flexible and let the user decide which adapter and/or IP to use. You'd probably want to create some kind of configuration form to do this.
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Just a matter of curiosity and general knowledge..easy question it seems but I didn't find an answer 
My project (I'm using VS2008) targets .net framework 3.5, but after compiling the IDLASM shows:
// Metadata version: v2.0.50727
and examining the loaded application, the used DLLs really points to the 2.05 framework...should'nt it target the 3.5 ?
Thanks for any help
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It is targetting 3.5. .NET 2.0, 3.0 and 3.5 all use the .NET 2.0 CLR.
.NET 3.0 and 3.5 are just set of extensions to the .NET Framework Class Libraries. Neither of them introduced any additional functionality to the .NET CLR.
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This is the answer I thought I'd get, but I found many articles refering to this as the required framework version. So, how can I get the required framework from the assembly file ?
Thanks a lot.
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The line you're look at is telling you the .NET CLR version that is required to execute the code, not the .NET Framework version. The CLR is the virtual machine runtime that executes the code. The Framework is the class library that supplies the functionality for the thousands of classes you can use in your code.
There is nothing in the metadata that specifies the .NET Framework version that is required to run the app. What you see in the manifest is the required .NET CLR version. Under that, you'll see a bunch of .assembly extern references. Each of these imports a namespace, specifying the public key and VERSION NUMBER the loader must bind to. Each reference can have it's own version number seperate from the rest. For example, if you create a blank WPF app targeting .NET Framework 3.5, you see the MSCORLIB is version 2.0, from .NET 2.0, SYSTEM from .NET 2.0, PresentationFramework from .NET 3.0, and WindowBase from .NET 3.0.
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I want to logout from my account totally and return control to the Login page
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manjusha s wrote: I want to logout from my account totally and return control to the Login page
Well then I suggest that you do so.
In the mean time, stop posting the same question over and over. If anybody either can, or is willing to help you they will, but they will not feel inclined to do so if you start spamming the forums.
Henry Minute
Do not read medical books! You could die of a misprint. - Mark Twain
Girl: (staring) "Why do you need an icy cucumber?"
“I want to report a fraud. The government is lying to us all.”
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Will you stop bumping this post.
A. This isn't the ASP.NET forum.
B. It's rude to bump posts.
C. You'll be ignored by people now.
"WPF has many lovers. It's a veritable porn star!" - Josh Smith As Braveheart once said, "You can take our freedom but you'll never take our Hobnobs!" - Martin Hughes.
My blog | My articles | MoXAML PowerToys | Onyx
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i am BSC(CS) graduate from mumbai, working as soft.developer in small accounting software company,basically i m working on .net-2008 and 2005 using vb as P-language,but now i want to switch to robotics technologies,
so can any one suggest me wht should be my first step to learn robotics PL and how can i switch my career to robotics field as coder.
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the page should be totally logged out from the account and control should pass directly to the Login page
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yes, I agree, the page should be totally logged out.
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Actually i have written
Response.Redirect("Login.aspx");
on logout button,but i want totally to be logged out from the account and the
control should pass to login page again..
Thanks in advance
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Stop making a new thread, when you are replying to a previous post.
Use the Reply rollover on the response you wish to reply to.
Henry Minute
Do not read medical books! You could die of a misprint. - Mark Twain
Girl: (staring) "Why do you need an icy cucumber?"
“I want to report a fraud. The government is lying to us all.”
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Hi Guys,
I'm trying to get my forms to clean up after themselves when i dispose them. The designer builds all the lovely disposal pattern stuff, with the body:
<br />
if (disposing && (components != null))<br />
{<br />
components.Dispose();<br />
}<br />
base.Dispose(disposing);<br />
Which is all well and good, but as i add components to the designer, i would assume they would be placed in a container and cleaned up when the form disposes, however, the container is always null, and hence the dispose is never called.
Because of this my background worker keeps running and my underlying win32 api calls are never closed down.
While i can (and will) do this the manual way, is there any way to have the designer wire up that logic for me?
Regards
Tris
-------------------------------
Carrier Bags - 21st Century Tumbleweed.
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