In Windows Application programming, many developers create the log file in the app directory which is not always available to a regular user and its not a good idea.

The log file should probably go in the AppData folder i.e. %appdata% as long as it can be opened from the application.

Here is the source code to get path of appdata folder then you can create another directory under the appfolder:

C# code:

// The folder for the roaming current user 
string appDataFolder = System.Environment.GetFolderPath(System.Environment.SpecialFolder.ApplicationData);

// Combine the base folder with your specific i.e. application folder....
string specificFolder = System.IO.Path.Combine(appDataFolder ,[ApplicationFolderName]);

VB.Net code:

' The folder for the roaming current user 
Dim appDataFolder As String =  System.Environment.GetFolderPath(System.Environment.SpecialFolder.ApplicationData) 
 
' Combine the base folder with your specific i.e. application folder....
Dim specificFolder As String =  System.IO.Path.Combine(appDataFolder,(ApplicationFolderName))

Happy Coding!!