Method Interception using Reflection in C# -


i wrote abstract class uses reflection find fields marked attribute in constructor, this:

[attributeusage(attributetargets.field)] public class trackedfield : attribute {}  public class atrackedobject {     public atrackedobject() {         type objtype = this.gettype();         foreach(fieldinfo f in objtype.getfields()) {             if(f.isdefined(typeof(trackedfield)), false)) {                 //add field list keep tabs on periodically             }         }     } }

what do, is:

  1. create attribute, trackedmethod
  2. in constructor, in same fashion trackedfields, find methods tagged trackedmethod
  3. change method when gets called, method inside atrackedobject gets called first or instead, either replacing method entirely or injecting code it, without breaking ability @ least see original method call was, including parameters
  4. no third-party libaries, , should .net 3.5 compatible

i have seen number of se threads discussing how this, , of answers relied on being able use third party library - however, none of questions seemed match use case - can ensure 100% every object needs have methods tracked inherit class tracking.

i don't know sure possible, wondering since ioc/aop libraries postsharp , others exist, surely must operate kind of mechanism - assume reflection.emit plays part - what, , how?

here similar questions, did not have seemed me answers specific scenario, or relied on third party libraries:

custom-attribute-to-process-info-before-a-method-is-called

how-do-i-intercept-a-method-call-in-c (this helpful, missing crucial component of how inject code

intercept-method-calls

is there way make technique (attribute -> base class constructor -> reflection -> method interception) viable?

could work need?

[attributeusage(attributetargets.field)] public class trackedfield : attribute { }  public class atrackedobject {     public atrackedobject()     {         type objtype = this.gettype();         foreach (fieldinfo f in objtype.getfields())         {             if (f.isdefined(typeof(trackedfield), false)) {                 if (f.fieldtype == typeof(action))                 {                     var currentvalue = f.getvalue(this) action;                     action newvalue = () =>                     {                         console.writeline($"tracking {f.name}");                         currentvalue.invoke();                     };                      f.setvalue(this, newvalue);                 }             }         }     }      [trackedfield]     public action somemethod = () => console.writeline("some method called"); }

this done simple action property extended use func<>

edit: forgot include usage , output.

usage:

static void main(string[] args) {     var obj = new atrackedobject();     obj.somemethod();      console.read(); }

output:

tracking somemethod method called

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