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.NET Forum / .NET Framework / CLR / July 2007Interacting with managed objects in a hosted CLR
I read the book "Customizing the MS .NET Framework CLR" By Steven Pratschner. It describes how to host the CLR in an application for example the way SQL Server hosts the CLR. It also describes in great details how to control the CLR, the way it behaves. What I am missing is, how does the host interact with the managed code in the hosted CLR? How does the host create instances and invoke methods on those instances? How does the host gets reply from the CLR? And how does the CLR communicates to the host, if a callback is needed? Thanks! PS: I am not sure if this is the right group. Hi Todor, As for custom CLR hosting scenario, if you want to communicate between your unmanaged hosting application and the managed CLR runtime, you should make use of the "AppDomainManager" (application domain manager). In .NET 2.0, each appdomain can have an AppDomainManager and we can get the reference to the AppDomainManager after it is created(or at initialize time). And for custom CLR hosting scenario, you can use some certain interface method to query the AppDomainManager interface pointer of the default AppDomain of your managed CLR runtime. #AppDomainManager Class http://msdn2.microsoft.com/en-us/library/system.appdomainmanager(VS.80).aspx #Mtps_DropDownFilterText for detailed description on this, you can refer to the "Application Domain Managers" section in the <Customizing the Microsoft .NET Framework Common language Runtime> book (by Steven Pratschner). It is in the Chapter 5(using application domain effectively). Hope this helps. Sincerely, Steven Cheng Microsoft MSDN Online Support Lead This posting is provided "AS IS" with no warranties, and confers no rights. Hello Todor! > I read the book "Customizing the MS .NET Framework CLR" By Steven > Pratschner. You too? ;-) > What I am missing is, how does the host interact with the managed > code in the hosted CLR? How does the host create instances Starting from the ICorRuntimeHost interface, you have to get the _AppDomain instance. The Domain may be the DefaultDomain (ICodeRuntimeHost.GetDefaultDomain), or you may start a new AppDomain (CreateDomain(Ex), ...) [_AppDomain] http://msdn2.microsoft.com/en-us/library/system._appdomain.aspx When you have the _AppDomain instance, you can use all Methods like "CreateInstance", or "CreateInstanceFrom" to create Objects. [_AppDomain.CreateInstance] http://msdn2.microsoft.com/en-us/library/system._appdomain.createinstance.aspx [_AppDomain.CreateInstanceFrom] http://msdn2.microsoft.com/en-us/library/system._appdomain.createinstancefrom.aspx > and invoke > methods on those instances? Maybe there are other methods, but I am only aware of one way to do this: You should make the Objects that you have to call from the unmanaged world COM-Visible. Then you can call methods using COM (as done within the CLR itself). I do not know how the SQL-Server integration has been managed. > How does the host gets reply from the > CLR? If I understand you correclty, you meen how the unmanaged Code gets Methodcalls, Data, ... from the managed Code? Well, it's just a matter of the Object-Model. If you have the ability to create objects, and call methods (with parameters) from this object, you have everything you need. If the managed Code should invoke unmanaged methods, you sould implement an COM-based "Context" Object which is passed to the managed Object as an Parameter. When the managed Code calls Methods from the Context-Object, it calls the unmanaged Code via COM Interop. With a proper Object-Model on the managed side, you can hide awai all this unamanged / COM Stuff from the implementor of the managed Components (if this is part of a bigger project). > And how does the CLR communicates to the host, if a callback is > needed? What kind of callback to you meen? :: GP Se inline. >> methods on those instances? > > Maybe there are other methods, but I am only aware of one way to do this: > You should make the Objects that you have to call from the unmanaged world > COM-Visible. Then you can call methods using COM (as done within the CLR > itself). I do not know how the SQL-Server integration has been managed. It would be nice to head how MSSQL have implemented this. COM is apparently the way to communicate to the CLR and to the host when it comes to objects. I have to questions here: 1. If a have a class X with method Y, do I have to register the class as COM server (gacutil.exe on the assembly, regasm.exe to make a typelib and register it in the registry) or can I access the class in-place, meaning that the COM interfaces are private to the class and the host only and the rest of the world has no knowledge of those. The idea is to keep the host machine clean and simplify deployment. 2. If I want to use an existing .Net class (from the host), let's say System.Text.StringBuilder, how would that class have to be registered with COM? >> How does the host gets reply from the >> CLR? [quoted text clipped - 3 lines] > the Object-Model. If you have the ability to create objects, and call > methods (with parameters) from this object, you have everything you need. I ment the return value. > If the managed Code should invoke unmanaged methods, you sould implement > an COM-based "Context" Object which is passed to the managed Object as an [quoted text clipped - 4 lines] > unamanged / COM Stuff from the implementor of the managed Components (if > this is part of a bigger project). Yes, so the way to go is let the host implement a COM server and have the CLR call the COM menthods in the host. Correct? Hi Todor, For custom CLR host scenario, the main approach to communicate between unmanaged world to the hosting CLR is using the AppDomainManager, you get the default domain's AppDomainmanager reference through certain interface, and then query some custom interfaces(you've defined in your custom AppDomainManager class). So what you need to do here is: ** define your own AppDomainManager class(managed class) ** in the AppDomainManager class, define some methods that can be correctly called from unmanaged code through COM interop interfaces At runtime, CLR will load your AppDomainManager class(you do not need to explicitly host it as a COM server). And at unmanaged part, you need to get reference to the AppDomainManager and query the certain interface(you've defined in your AppDomainManger class). As I mentioned in the previous message, you can refer to the "Application Domain Managers" section in the <Customizing the Microsoft .NET Framework Common language Runtime> book (by Steven Pratschner). It is in the Chapter 5(using application domain effectively). Sincerely, Steven Cheng Microsoft MSDN Online Support Lead This posting is provided "AS IS" with no warranties, and confers no rights. Hi Todor, Have you got any further progress or does the infornmation mentioned in previous message also helps a little? If there is anything else we can help, please feel free to post here. Sincerely, Steven Cheng Microsoft MSDN Online Support Lead This posting is provided "AS IS" with no warranties, and confers no rights. Hi Steven, no further questions for the moment. I'll have to spend some time playing with the technology. Take care! -- Todor > Hi Todor, > [quoted text clipped - 10 lines] > This posting is provided "AS IS" with no warranties, and confers no > rights. Thanks for your followup Todor, Welcome to post any of your progress or result here. Good luck! Sincerely, Steven Cheng Microsoft MSDN Online Support Lead This posting is provided "AS IS" with no warranties, and confers no rights.
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