How to use reflection for accessing object from its name as a string

Question

Ive a folder monitoring application where around 25 filewatchers monitoring 25 folders. Each of the filewatchers named fsw1,fsw2 ....

bCreateFileCheck = True
fsw1 = New FileSystemWatcher(My.Settings.UserRootFolder1)
fsw1.IncludeSubdirectories = True
fsw1.EnableRaisingEvents = True
fsw1.NotifyFilter = (NotifyFilters.LastAccess Or NotifyFilters.LastWrite Or NotifyFilters.FileName)

So this is repeating for the 25 folders, but only difference is name changing of fsw1 to fsw2,fsw3 etc. and also My.Settings.UserRootFolder1 to My.Settings.UserRootFolder2,My.Settings.UserRootFolder3 etc.

So how can we achieve this using for loop without writing individual code blocks for every filewatchers. I guess using some reflection techniques it can be achieved.

Nico Schertler · Accepted Answer · 2017-02-16 07:57:28Z

2

Don't make your life harder than it needed to be. Use an array (or List(Of T) if you need something flexible):

Dim watchers(24) As FileSystemWatcher
For i As Integer = 0 To watchers.GetUpperBound(0)
    Dim path = CStr(My.Settings.Item("UserRootFolder" & (i + 1)))
    watchers(i) = New FileSystemWatcher(path)
    'Do further initialization...       
Next

If the structure is fixed and you cannot really change it, you can set the variables to the objects that you created in the For loop. So change the loop as follows:

'...
Dim watcher = New FileSystemWatcher(...)
Me.GetType().GetField("fsw" & (i + 1)).SetValue(Me, watcher)

This gets the field with the appropriate name and sets its value to the object that you just created (I assume that it is a field based on its naming).

edited Feb 16, 2017 at 7:57

answered Feb 16, 2017 at 7:24

Nico Schertler

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3 Comments

Sandeep Thomas Over a year ago

Sorry friend, actually its an existing code on the project been runnning for 3 4 years i guess. So there is lots of places where its using. So any possibility with that way other than array?

Nico Schertler Over a year ago

Then I would strongly recommend refactoring the code. If that is not an option, I have added some more information to my answer.

Sandeep Thomas Over a year ago

Thats really nice my friend.. Thanks for that.. Made my day

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