CODEWITHSUNDEEP
c#servicefilesystemwatcher
On The Net Again
On The Net Again

Reputation: 305

Which is the right way to add the Change Event for a FileSystemWatcher?

Which is the proper way to add the Changed Event?

    public static void WatchFileForChange()
        {
            FileSystemWatcher fsw = new FileSystemWatcher();

            fsw.Path = Path.Join(System.Configuration.ConfigurationManager.AppSettings["AccessDBFolder"]);
            fsw.Changed += new FileSystemEventHandler(UpdateMDBChange);
            fsw.Filter = "*.mdb";
            fsw.NotifyFilter = NotifyFilters.FileName | NotifyFilters.LastWrite;
            fsw.EnableRaisingEvents = true;
            fsw.IncludeSubdirectories = true;
        }

        private static void UpdateMDBChange(object sender, FileSystemEventArgs e)
        {
            //https://stackoverflow.com/a/3042963/6067603
            DateTime lastWriteTime = File.GetLastWriteTime(e.FullPath);
            if (lastWriteTime.Ticks - lastRead.Ticks > 100000)
            {
                TestClient().Wait();
                lastRead = lastWriteTime;
            }
        }

Is it fsw.Changed += new FileSystemEventHandler(UpdateMDBChange); or fsw.Changed += UpdateMDBChange;

Both ways seem to fine. But I don't know if there's a technical issue that could occur. Or if a certain way is frowned upon.

Upvotes: 0

Views: 115

Answers (2)

Adam Benson
Adam Benson

Reputation: 8522

They're identical under the hood.

Here's the disassembly:

            ed.MyEvent += Ed_MyEvent;
00007FFDF3D05F22  mov         rcx,7FFDF3DD4F00h  
00007FFDF3D05F2C  call        CORINFO_HELP_NEWSFAST (07FFE5384AF00h)  
00007FFDF3D05F31  mov         qword ptr [rbp+28h],rax  
00007FFDF3D05F35  mov         r8,offset CLRStub[MethodDescPrestub]@7ffdf3cfc768 (07FFDF3CFC768h)  
00007FFDF3D05F3F  mov         rcx,qword ptr [rbp+28h]  
00007FFDF3D05F43  xor         edx,edx  
00007FFDF3D05F45  mov         r9,offset CLRStub[StubLinkStub]@7ffdf3bcd070 (07FFDF3BCD070h)  
00007FFDF3D05F4F  call        Method stub for: System.MulticastDelegate.CtorOpened(System.Object, IntPtr, IntPtr) (07FFDF3CF4568h)  
00007FFDF3D05F54  mov         rcx,qword ptr [rbp+38h]  
00007FFDF3D05F58  mov         rdx,qword ptr [rbp+28h]  
00007FFDF3D05F5C  cmp         dword ptr [rcx],ecx  
00007FFDF3D05F5E  call        CLRStub[MethodDescPrestub]@7ffdf3d059b8 (07FFDF3D059B8h)  
00007FFDF3D05F63  nop  

            ed.MyEvent += new dlgEvent(Ed_MyEvent);
00007FFDF3D05F64  mov         rcx,7FFDF3DD4F00h  
00007FFDF3D05F6E  call        CORINFO_HELP_NEWSFAST (07FFE5384AF00h)  
00007FFDF3D05F73  mov         qword ptr [rbp+20h],rax  
00007FFDF3D05F77  mov         r8,offset CLRStub[MethodDescPrestub]@7ffdf3cfc768 (07FFDF3CFC768h)  
00007FFDF3D05F81  mov         rcx,qword ptr [rbp+20h]  
00007FFDF3D05F85  xor         edx,edx  
00007FFDF3D05F87  mov         r9,offset CLRStub[StubLinkStub]@7ffdf3bcd070 (07FFDF3BCD070h)  
00007FFDF3D05F91  call        Method stub for: System.MulticastDelegate.CtorOpened(System.Object, IntPtr, IntPtr) (07FFDF3CF4568h)  
00007FFDF3D05F96  mov         rcx,qword ptr [rbp+38h]  
00007FFDF3D05F9A  mov         rdx,qword ptr [rbp+20h]  
00007FFDF3D05F9E  cmp         dword ptr [rcx],ecx  
00007FFDF3D05FA0  call        CLRStub[MethodDescPrestub]@7ffdf3d059b8 (07FFDF3D059B8h)  
00007FFDF3D05FA5  nop  
}

I don't pretend to know what all those instructions are but you can see they're the same.

So the answer to your question is, "it doesn't matter".

Upvotes: 5

Funk
Funk

Reputation: 11201

This is called method group conversion. It allows you to replace the more verbose

fsw.Changed += new FileSystemEventHandler(UpdateMDBChange);

by directly supplying the method name

fsw.Changed += UpdateMDBChange;

Basically, it's syntactic sugar, a feature added later on so you could type less. The type of the event handler can be inferred and doesn't need to be declared explicitly.

Upvotes: 4

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