Keep variable in memory until system reboot

Question

There is a way to keep a variable in the memory of the machine until it restarts?

My application made a change in the system and sent the message to the user to restart the machine, to prevent any problem I have to detect if the machine has already been restarted even if close the program and start again.

I figured maybe I could use to create an address in memory marking that the machine needs to restart and store in the application settings the address of that variable, even if they restarted the program it would test if the position in memory indicates that it needs to restart...

As I have little knowledge in the "lower level" area of C# I don’t know if it would actually store the variable or if there is a correct form for it.

Answer 1

Marcus, as Maniero pointed out, you can’t keep a variable in memory, but you can save a flag stating that the system needs to be restarted, perhaps the easiest solution is to change the app.config.

var config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
config.AppSettings.Settings["Restart"].Value = "true";
config.AppSettings.Settings["Data"].Value = DateTime.Now.ToString("o");
config.Save(ConfigurationSaveMode.Modified);

if you need more data, you can choose to store a JSON file in some system folder (the example below uses the Newtonsoft.Json):

var dados = new { MustRestart = true, Data = DateTime.Now, Foo = "Hello", Bar = "World" };
var json = JsonConvert.SerializeObject(dados);
System.IO.File.WriteAllText(AppDomain.CurrentDomain.BaseDirectory + "\dados.json", json);

If you have some kind of paranoia and want to prevent the user from modifying these values, you have two options, to store this data using Sqlite with SEE(Sqlite Encryption Extension). you can see more about.:

• Sqlite Encryption Extension
• Dapper + Sqlite

finally you can send a request to a WebAPI and this will update a flag informing that the machine needs to be restarted, this approach has two negative points, the client needs an internet connection and you need to implement and host the WebAPI.

As to whether the machine has been restarted, you can read the Windows records as follows, then just scan the entries.:

var eventLog = new System.Diagnostics.EventLog(); 
//eventLog.Source = ""; O ideal que informe o nome do Log que possui os eventos de inicialização do sistema.
foreach (var entry in eventLog.Entries) 
{
   Console.WriteLine(entry.Message);
}

Answer 2

I find this a little strange, it seems to me that the solution to the problem should even be other. But answering the question, it is neither possible in C#, nor in any language to keep application data in memory when it is not running.

But you can get the same result by keeping data in a file. What has nothing low level.