How to update your exe from remote host - c# 4.0 - wpf application

Question

I want to update my exe from remote server. So when the button clicked on my wpf application it will download the remote and also a remote txt file and replace the current ones in the same folder that exe running. So it will overwrite the current txt and and exe file while my exe is running. How can i achive this ?

Remote host is url like www.mydomain.com/MyAPP.exe

wpf application , c# 4.0

Answer 1

The way that we resolved this issue was to create a shell exe that as the one that was installed and deployed initially to the client machines.

The "real" executable program is stored in a subdirectory of this initial app. When the shell app is launched, after it has downloaded and installed any updates for the real app, it launches the real app's executable in a separate AppDomain.

Here is the core of the "real" app launching from within the shell app:

        System.AppDomainSetup oSetup = new System.AppDomainSetup();
        string sApplicationFile = null;

        // Use this to ensure that if the application is running when the user performs the update, that we don't run into file locking issues.
        oSetup.ShadowCopyFiles = "true";
        oSetup.ApplicationName = sAppName;

        // Generate the name of the DLL we are going to launch
        sApplicationFile = System.IO.Path.Combine(sApplicationDirectory, sAppName + ".exe");

        oSetup.ApplicationBase = sApplicationDirectory;
        oSetup.ConfigurationFile = sApplicationFile + ".config";
        oSetup.LoaderOptimization = LoaderOptimization.MultiDomain;

        // Launch the application
        System.AppDomain oAppDomain = AppDomain.CreateDomain(sAppName, AppDomain.CurrentDomain.Evidence, oSetup);
        oAppDomain.SetData("App", sAppName);
        oAppDomain.SetData("User", sUserName);
        oAppDomain.SetData("Pwd", sUserPassword);

        oAppDomain.ExecuteAssembly(sApplicationFile);

        // When the launched application closes, close this application as well
        Application.Exit();

Note that in our version, the shell app collects the user name and password from the user in order to access the update web site correctly. This data is then passed to the "real" app through the SetData method on the AppDomain.

Answer 2

The solution depends on your particular case. But there's no straight solution, because you can't update assemblies while they are loaded into memory and being used. I can propose 2 solutions: using shadow copying and using some sort of helper executable. I've used both of them.

Shadow copying.

The obvious way is to make your main executable to be shadow copied, replace it while your app is running and then restart the app. But you can't make your default app domain to be shadow copied, only secondary app domains can be. But you still can move all your code into another assembly (say, MainAppLib.dll) and rewrite your main app executable (MainApp.exe) so that it contains only "loader code". This loader code has to create another app domain, set it to be shadow copied and then run your program logic in the secondary app domain. Beware not to have any direct references from your main app domain into MainAppLib.dll because then this assembly will be loaded into your main app domain which is not shadow copied and the assembly file will get locked. In most cases you can go with AppDomain.ExecuteAssembly() methods.

Helper executable

The idea is to use some sort of update finisher. Your main app remains unchanged, you only add a little amount of code into it, so that your app will download update, put it into temporary folder, and then your main app starts update finisher (in separate process) and exits. Update finisher waits till your app closes and then copies new files from temporary folder into your app folder replacing all files. Update finisher can't replace it's own executable but it can be done by main application before it starts the update finisher. After copying files update finisher runs your application.

p.s. Personally I prefer the former solution because it involves some sort of voodoo magic using app domains, reflection, assemblies e.t.c. And it can be evolved into using plugins if you need (e.g. via MEF framework). But the latter is easier to understand especially if you have never worked with app domains and manual assemblies loading, it's quite straightforward.

Answer 3

You could probably use ClickOnce (based on your comment above that you would be prepared to have another assembly get the exe....as the other poster mentioned you can't replace a running assembly). You can configure it to check at various times (e.g. on startup) for new versions and it automatically downloads them. Its a very robust solution and you can do a lot with the deployment assemblies.