Today I faced a specific need withing a WPF application: I have a well-tested and already in production code which works well for a given user and I need to create an application to execute the same “one-thread\/context” code for a lot of users at the same time. <\/strong>The code uses a lot of static fields, properties and can’t be run as it is in different threads.
\n<\/p>\n

The solution I ended up with is to create an AppDomain by “worker” and to execute the already existing code in each one. The context will be unique in each AppDomain and I will be able to reuse my existing code.<\/strong><\/p>\n

To have this working I have to perform these steps:<\/p>\n

\n
• Create a new class project “MaDllAPart” on which I add a reference to my existing code assembly.<\/li>\n
• Create a new class “StartPoint” in it which inherits from MarshalByRefObject. This will let it be called from another AppDomain (my new WPF application in this case).<\/li>\n
• Add an “Execute” Method to my StartPoint class which calls my legacy code.<\/li>\n
• Create an AppDomain by thread, instanciate a StartPoint in this AppDomain.<\/li>\n
• Instanciate a StartPoint in this AppDomain and call it’s Execute method.<\/li>\n<\/ul>\n

  <\/p>\n

  The code for the StartPoint class is very easy :<\/p>\n

  \r\npublic class MonPointDentree : MarshalByRefObject\r\n{\r\n    public static string Context;\r\n\r\n    public void Execute(string input)\r\n    {\r\n        \/\/ Task can't be marshalled : let's wait\r\n        ExecuteAsync(input).Wait();\r\n    }\r\n\r\n    private async Task ExecuteAsync(string input)\r\n    {\r\n        Debug.WriteLine(\"[BEFORE] \" + Context);\r\n        Context = input;\r\n        Debug.WriteLine(\"[AFTER] \" + Context);\r\n\r\n        \/\/ call my legacy code here\r\n    }\r\n}\r\n<\/pre>\n
  The “MaDllAPart” is added as a reference to the WPF project : this let’s me create an instance of StartPoint without special configuration from my side. Be sure to use the full name (with the namespace) of the instanciated type.<\/p>\n
  \r\nprivate static void LaunchProcess()\r\n{\r\n    for (int i = 0; i < 10; i++)\r\n    {\r\n        var domain = AppDomain.CreateDomain(\"MonAppDomain_\" + i);\r\n\r\n        var startPoint = (MonPointDentree)domain\r\n            .CreateInstanceAndUnwrap(\"MaDllAPart\", \"MaDllAPart.StartPoint\");\r\n\r\n        startPoint.Execute(\"module \" + i);\r\n    }\r\n}\r\n<\/pre>\n
  Happy coding !<\/p>\n","protected":false},"excerpt":{"rendered":"
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