Separate execution without application domain

Question

Hi friends As we know that if we want separate execution of different different application on .NET framework we use application domain but if we want same thing without application domain  is it possible or not ? if yes then plz. explain Thanks

Sam Hobbs · Answer

Yes there has always been a one-for-one correspondence of process handles and process ids. Somehow Domains violate that rule. I have not explored what the OpenProcess Windows API function does when it is given a process id of a process with multiple domains in it. OpenProcess assumes there is only one process for a process handle. I am tempted to say it is Microsoft shenanigans but when I look up shenanigans it seems to harsh. I do think however that it is Microsoft using confusing terminology. I just don't know if it is marketing people or technical people in Microsoft that decided use the exe extension for executable code that is so different from any other type of executable code except for possibly Java executable files.

Vulpes · Answer

It's interesting that the process handles are different for the two assemblies. The only way I know of to create a new process handle is by calling the CreateProcess function but presumably this is not being called twice because both assemblies are within the same process. I find that rather strange :-/

Sam Hobbs · Answer

It was late in the day when I posted my last reply. Attached is a project with a modified version of what Vulpes posted. My directory structure is different from what Vulpes used so the path to the second application is different plus I used different names. This version shows a little more. First note that the process handle (Process.Handle) is different for the two applications. If however we use GetProcessId to get the process id for the handle then we get the same process id.

Vulpes · Answer

Yes I'd agree with that Sam.

Sam Hobbs · Answer

To continue what you were saying Vulpes I suggest it is more significant to say (if it is true) that you can't have more than one unmanaged exes in a process. Then we can proceed by making it clear that the relevant Microsoft documentation says nothing about exe files (correct?); it uses the term assembly. Until Microsoft releases a new version of Windows that supports managed code as the native format normal exe files are exe files that are either unmanaged entirely or that begin execution as an unmanaged exe.

Deepak Dwij · Answer

Gud explanation Vulpes Thanks

Vulpes · Answer

Well it depends what you mean by an .exe :) An application domain executes an assembly and it's possible for an assembly to have the .exe file extension. However it's not a 'normal' .exe because it contains IL and metadata rather than native code. Here's a quick example of two .NET exes running in different application domains within a single process: // domaintester.cs using System; using System.Diagnostics; class Program { static void Main() { AppDomain currentDomain = AppDomain.CurrentDomain; string procName = Process.GetCurrentProcess().ProcessName; if (currentDomain.IsDefaultAppDomain()) { Console.WriteLine(Hello from the default domain in {0} procName); } AppDomain testDomain = AppDomain.CreateDomain(TestDomain); testDomain.ExecuteAssembly(testdomain.exe); Console.ReadKey(); } } // testdomain.cs using System; using System.Diagnostics; class Program { static void Main() { AppDomain currentDomain = AppDomain.CurrentDomain; string procName = Process.GetCurrentProcess().ProcessName; if (!currentDomain.IsDefaultAppDomain()) { Console.WriteLine(Hello from {0} in {1} currentDomain.FriendlyName procName); } } } When you build these two files to domaintester.exe and testdomain.exe respectively and then run the former you should see the following output: Hello from the default domain in domaintester Hello from TestDomain in domaintester Although you can have two (or more) .NET .exes running in the same process Sam's probably right that you can't have more than one 'normal' .exe running within a single process.

Sam Hobbs · Answer

Microsoft has a way of confusing us by explaining a lot of stuff but hiding some critical details where it is difficult to find. The thing I suspect they are hiding from us is what does an application domain execute. I can't find the answer to that and it is not important to me to find the answer but I will be very surprised if it is possible to execute more than one exe file in a process . Am I wrong? Is there any possible way to violate the rule that there is always one exe file corresponding with each and every process ?

Vulpes · Answer

To be absolutely accurate a .NET application always runs in an application domain even though there's usually only one (the 'default domain') within a process. The default domain is created automatically by the CLR and doesn't require any programmer intervention. So the strict answer to the question is that it isn't possible for a .NET application to run in anything other than an application domain :)

Deepak Dwij · Answer

Thanks vulpes.... r u sure ?

Sam Hobbs · Answer

Domains are relatively new for Windows. It is extremely normal for execution of Windows applications to be in separate processes. Except for ASP applications nearly all Windows applications execute in separate processes.

Vulpes · Answer

Hi Deepak Yes you can still run multiple .NET applications concurrently by executing each one in a separate process rather than a separate application domain within the same process. Doing so uses more operating system resources and makes communication between applications more difficult. However .NET still has mechanisms which allow for inter-process communication including pipes and memory-mapped files.