c# - pre and post actions to an existing class method -

i’m novice in c# , need help. need implement series of wrappers functions perform pre , post action besides original method.

this way (one function example):

class {        public streamwriter writer;          public bool writeln(string texttowrite)//wrapper writer.write(string)        {               preaction();               this.writer.write(texttowrite);               postaction();        }  } 

related scenarios - tracing each function entry (so signature of post , pre void post() , iterating method parameters through reflection).

i need done on numerous classes , functions- wrapping each 1 tedious, if change need reopen code many times. solution can think of (instead of composition-see attached code above) inheriting streamwriter , overriding base method, again multiple classes , functions isn’t pretty, can think or know of different way doing that?

br, mosh.

you write wrapper class , either pass constructor of class want wrap methods of, or have class create wrapper class itself.

it still rather fiddly, let put wrapper logic 1 class.

an example clarify. class demo shows how use wrapper class. note wrapper class allows detect exceptions (while ensuring exceptions still thrown).

argument-checking logic omitted brevity:

using system; using system.io;  namespace consoleapp1 {     public sealed class wrapper     {         public wrapper(action pre, action<exception> post)         {             _pre  = pre;             _post = post;         }          public t wrap<t>(func<t> func)         {             try             {                 _pre();                 t result = func();                 _post(null);                 return result;             }              catch (exception exception)             {                 _post(exception);                 throw;             }         }          public void wrap(action action)         {             try             {                 _pre();                 action();                 _post(null);             }              catch (exception exception)             {                 _post(exception);                 throw;             }         }          private readonly action _pre;         private readonly action<exception> _post;     }      public sealed class demo     {         public demo(wrapper wrapper)         {             _wrapper = wrapper;         }          public string name()         {             return _wrapper.wrap(() => "this name");         }          public void write(string texttowrite)         {             _wrapper.wrap(() => _writer.write(texttowrite));         }          public void throwsexception()         {             _wrapper.wrap(() => {throw new invalidoperationexception("test");});         }          private readonly wrapper      _wrapper;         private readonly streamwriter _writer = new streamwriter(console.openstandardoutput());     }      sealed class program     {         private void run()         {             var wrapper = new wrapper             (                 () => console.writeline("calling pre()"),                 ex => console.writeline("calling post(), exception = " + ((ex != null) ? ex.message : "<none>"))             );              demo demo = new demo(wrapper);              console.writeline("name = " + demo.name());             demo.write("some text write");             demo.throwsexception();         }          private static void main()         {             new program().run();         }     } }