Is it possible to have multiple assemblies in a Application Domain
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From: Tony Johansson on 2 May 2010 08:17 Hi! I know that Application is about isolation code in an assembly. It is useful because it can improve reliability and Efficiency. But there is one thing that I still have some doubt about and that is if you can have multiple assemblies in an Application Domain. For example in the code example below I load three assemblies(AssemblyA,AssemblyB and AssemblyC) into the Application Domain named New Domain. I got the following answer to this question when I asked this question on a thread. "My reading of the docs, along with a simple experiment, show that the code ExecuteAssemblyByName does not return until the executable (such as AssemblyA.exe) is finished. There is no threading nor switching as they are executed in order. They are not executed in parallel." This mean that you can only have one and only assembly running in the Application Domain at any given time. The strange thing is that in the Microsoft Press(exam 70-536) book that I read is two things that talk in favour that you can have multiple assemblies in an Application Domain and that is the following two points. 1. There is a figure drawn in the book that shows two assemblies in an Application Domain 2.There is a method in Appdomain that is named GetAssemblies that says "Gets the assemblies that have been loaded into the execution context of this application domain." static void Main(string[] args) { AppDomain myAppDomain = AppDomain.CreateDomain("New Domain"); myAppDomain.ExecuteAssemblyByName("AssemblyA"); myAppDomain.ExecuteAssemblyByName("AssemblyB"); myAppDomain.ExecuteAssemblyByName("AssemblyC"); } I have also tested this small main and it's true that AssemblyB will not start executing until AssembyA has finished executing. Normally books are correct so I want to be sure what is right in this matter if an Application Domain can have multiple assemblies or not ? //Tony
From: Alberto Poblacion on 2 May 2010 10:13 "Tony Johansson" <johansson.andersson(a)telia.com> wrote in message news:ugZOrFf6KHA.3892(a)TK2MSFTNGP02.phx.gbl... > But there is one thing that I still have some doubt about and that is if > you can have multiple assemblies in an Application Domain. > I have also tested this small main and it's true that AssemblyB will not > start executing until AssembyA has finished executing. > > Normally books are correct so I want to be sure what is right in this > matter if an Application Domain can have multiple assemblies or not ? To better understand Application Domains, please remember that all .Net code ALWAYS executes in an AppDomain, even if you didn't create any explicitly. For instance, if you create a plain and ordinary .exe application and you run it from Windows, a default appdomain will be created and your application will load into it. Can the AppDomain have multiple assemblies? Of course. That happens every time your .exe calls a .dll. You then have the exe and the dll (which are two assemblies) loaded into memory. It also happens if you call Assembly.Load() or Assembly.LoadFrom(). These methods load a new assembly into the same AppDomain that calls them. You don't even need to load the assemlies from a different domain. Can the AppDomain execute several assemblies in parallel? Sure. Just call Thread.Start() to launch another thread, and invoke code from a different assembly from within that thread. Can several AppDomains execute in parallel? Yes. Use the same thread that you started in the paragraph above to create a new appdomain and load and execute an assembly in that appdomain. Voila! You have two threads executing in two AppDomains.
From: Patrice on 2 May 2010 10:37 Hello, It seems you are confusing assemblies and threads. An assembly is just a deployment unit, most of the time a single file. So yes an application domain can use multiple assemblies just as an old win32 app can load several DLLs... Now an assembly is just a file, it has nothing to do with how the code run. So if you application have a single thread, only this thread will run. If your application have multiple threads, you'll be able to run some code in parallel (and the code running in parallel could be in a single assembly or in multiple assemblies, assemblies and threads being unrelated)... -- Patrice
From: Tony Johansson on 2 May 2010 10:54 Really good answer Alberto Poblacion !!! //Tony "Alberto Poblacion" <earthling-quitaestoparacontestar(a)poblacion.org> skrev i meddelandet news:e7hQ8Gg6KHA.5548(a)TK2MSFTNGP04.phx.gbl... > "Tony Johansson" <johansson.andersson(a)telia.com> wrote in message > news:ugZOrFf6KHA.3892(a)TK2MSFTNGP02.phx.gbl... >> But there is one thing that I still have some doubt about and that is if >> you can have multiple assemblies in an Application Domain. >> I have also tested this small main and it's true that AssemblyB will not >> start executing until AssembyA has finished executing. >> >> Normally books are correct so I want to be sure what is right in this >> matter if an Application Domain can have multiple assemblies or not ? > > To better understand Application Domains, please remember that all .Net > code ALWAYS executes in an AppDomain, even if you didn't create any > explicitly. For instance, if you create a plain and ordinary .exe > application and you run it from Windows, a default appdomain will be > created and your application will load into it. > Can the AppDomain have multiple assemblies? Of course. That happens > every time your .exe calls a .dll. You then have the exe and the dll > (which are two assemblies) loaded into memory. It also happens if you call > Assembly.Load() or Assembly.LoadFrom(). These methods load a new assembly > into the same AppDomain that calls them. You don't even need to load the > assemlies from a different domain. > Can the AppDomain execute several assemblies in parallel? Sure. Just > call Thread.Start() to launch another thread, and invoke code from a > different assembly from within that thread. > Can several AppDomains execute in parallel? Yes. Use the same thread > that you started in the paragraph above to create a new appdomain and load > and execute an assembly in that appdomain. Voila! You have two threads > executing in two AppDomains. > >
From: Family Tree Mike on 2 May 2010 11:22
On 5/2/2010 8:17 AM, Tony Johansson wrote: > Hi! > > I know that Application is about isolation code in an assembly. > It is useful because it can improve reliability and Efficiency. > > But there is one thing that I still have some doubt about and that is if you > can have multiple assemblies in an Application Domain. For example in the > code example below I load three assemblies(AssemblyA,AssemblyB and > AssemblyC) into the Application Domain named New Domain. > I got the following answer to this question when I asked this question on a > thread. > "My reading of the docs, along with a simple experiment, show that the > code ExecuteAssemblyByName does not return until the executable (such as > AssemblyA.exe) is finished. There is no threading nor switching as they > are executed in order. They are not executed in parallel." > This mean that you can only have one and only assembly running in the > Application Domain at any given time. > The strange thing is that in the Microsoft Press(exam 70-536) book that I > read is two things that talk in favour that you can have multiple assemblies > in an Application Domain and that is the following two points. > 1. There is a figure drawn in the book that shows two assemblies in an > Application Domain > 2.There is a method in Appdomain that is named GetAssemblies that says "Gets > the assemblies that have been loaded into the execution context of this > application domain." > > static void Main(string[] args) > { > AppDomain myAppDomain = AppDomain.CreateDomain("New Domain"); > myAppDomain.ExecuteAssemblyByName("AssemblyA"); > myAppDomain.ExecuteAssemblyByName("AssemblyB"); > myAppDomain.ExecuteAssemblyByName("AssemblyC"); > } > > I have also tested this small main and it's true that AssemblyB will not > start executing until AssembyA has finished executing. > > Normally books are correct so I want to be sure what is right in this matter > if an Application Domain can have multiple assemblies or not ? > > //Tony > > I probably should have written: "They assemblies are not executed in parallel in your example." Certainly as the other have pointed out, you could have executed them in parallel by putting each call into a separate thread. As has been pointed out, several dlls can be in a single app domain. You would not use (necessarily) ExecuteAssembly* to do this. You might use AppDomain.Load("path to dll"), for example, to load a bunch of assemblies that you later wish to remove. -- Mike |