关于.net影子复制的问题

心已赠人 2021-11-01 11:50 245阅读 0赞

I have the following problem when creating an [AppDomain][] and loading an  
assembly:  
I followed the steps described as anywhere i looked for documentation  
regarding this issue and the result is not quite what I expected. I obtain a  
shadow copy of my dll, but both files, the original and the shadow copied  
dll are locked by the process.  
Here is a piece of the code, please tell me what is wrong with it and what  
should i do for the original dll not to be locked anymore  
  
System. [AppDomainSetup][] appDomainSetup = new [AppDomainSetup][]();  
  
appDomainSetup. Shadow CopyDirectories = "D:\\\\pathToMyApp\\\\bin\\\\Debug";  
appDomainSetup. Shadow CopyFiles = "true";  
appDomainSetup.CachePath = "D:\\\\pathToMyApp\\\\bin\\\\Debug";  
appDomainSetup.ApplicationName = "appName";  
  
System. [AppDomain][] appDomain = System. [AppDomain][].CreateDomain("Domain" +  
"someName",  
new System.Security.Policy. [Evidence][]( [AppDomain][].CurrentDomain.Evidence),  
appDomainSetup);  
  
System.Reflection. [AssemblyName][] assemblyName =  
System.Reflection. [AssemblyName][].GetAssemblyName("pathToTheDll");  
  
System.Reflection. [Assembly][] assembly = appDomain.Load(assemblyName);  
  
I also tried using the Load(byte\[\] buffer) version of [AppDomain][].Load, but in  
this case, the shadow copy is not created anymore but the original dlls is  
used by the application, which, by the way, seems very strange to me.  
\---------------------------------------------------------------------------------  
The problem lies in the way [AppDomain][].Load() works.  
  
When you make a call to [AppDomain][].Load, the assembly is loaded in the  
target domain (which is appDomain in your case) BUT the call returns a  
reference to the same assembly back to your parent domain (the one  
where the code is running). When this happens, the dll gets loaded in  
the parent domain where there is no setting to shadow copy the files.  
  
So you see, shadow copy is working for the target domain, but it  
doesn't happen in the parent domain. Hence, the file gets locked.  
  
If you want to load the assembly in the target domain without getting  
a reference back in the parent domain, you will have to write a class  
that will load the assembly for you in the target domain. i.e.,  
something like a proxy object where you would first create an instance  
of the Loader object in the target domain and then call  
Loader.LoadMyAssembly(filename) which would load the specified file in  
the target domain and NOT return any reference to it. The only caveat  
is that you should never get a direct reference to the loaded  
assembly, even if it just an interface. The moment you do that, it  
will get loaded in your parent domain and you're back at square one.  
  
There is an excellent article on this topic by Eric Gunnerson on MSDN  
called ' AppDomains and Dynamic Loading'. You should take a look at  
that.

转载于:https://www.cnblogs.com/jmax/archive/2009/09/28/1575765.html

[AppDomain]: http://www.dotnet247.com/247reference/System/AppDomain.aspx
[AppDomainSetup]: http://www.dotnet247.com/247reference/System/AppDomainSetup.aspx
[Evidence]: http://www.dotnet247.com/247reference/System/Security/Policy/Evidence.aspx
[AssemblyName]: http://www.dotnet247.com/247reference/System/Reflection/AssemblyName.aspx
[Assembly]: http://www.dotnet247.com/247reference/System/Reflection/Assembly.aspx