I wonder if I delete App.config file, then copy my application to other pc, is it have any strange behavior?

Nope, it should be fine. There are various (somewhat tortuous) rules about exactly what version of the CLR etc gets used in what situations, but for the most part you're fine to just rely on the default behaviour.

You really don't need an app.config file unless you need to give specific settings.

Hello ,

Good to see you in Microsoft Community.

Can you provide more detailed information about the app, such as software name, version, etc.? Since some software due to its security policy limitations, really cannot clean up the associated files, resulting in a reinstallation that cannot be done as well as the first installation.

Alternatively, you can search and delete software-related entries in the registry: Open the Registry Editor by pressing Win + R and typing "regedit", use the F3 key, enter the name of your software, then search and delete the entries found. You may need to repeat this process until no relevant entries are found.

Disclaimer*: Generally, modifying registry subkeys or workgroups is intended for advanced users, administrators, and IT Professionals. It can help fix some problems,* h owever, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For further protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click How to back up and restore the registry in Windows (microsoft.com) to view the article.

Alternatively, you can check the Appdata directory (Win + R and type "%appdata%" then press Enter) to see if there is a folder related to the application. If so, please back up the directory to another location and then delete it.

Show hidden folders:

Win + R to open "Run", type "Control folders" to open the File Explorer Options*, switch to the "View" tab, then check "Show hidden files, folders or drivers", then* OK*.*

If anything is unclear, please do not hesitate to let me know.

Best Regards,

Mosken_L - MSFT | Microsoft Community Support Specialist

You can use something like this:

 m_Configuration = System.Configuration.ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
 m_Configuration.AppSettings.Settings.Remove(key);
 m_Configuration.AppSettings.Settings.Add(key, value);
 m_Configuration.Save(ConfigurationSaveMode.Modified);