Pass values from BackgroundWorker DoWork to BackgroundWorker Completed

backgroundworker, byval, pass-by-value, variables, vb.net

Solution

When you declare your `DoWork` function, note that it has some handy arguments built in :

Private Sub backgroundWorker1_DoWork(sender As Object, e As DoWorkEventArgs) _
                                                  Handles backgroundWorker1.DoWork

and also note similar arguments for the `RunWorkerCompleted` handler :

Private Sub backgroundWorker1_RunWorkerCompleted(ByVal sender As Object, _
                                          ByVal e As RunWorkerCompletedEventArgs) _
                                       Handles backgroundWorker1.RunWorkerCompleted

Critically, you have access to `e.Result`, which can be any object, in the `RunWorkerCompletedEventArgs`, and also `e.Result` in your `DoWorkEventArgs` - the latter is passed to the former when the method completes so at the end of your worker method just set :

e.Result = myResult

and then in your `RunWorkerCompleted` handler you can access it also via :

if e.Result = (whatever) then 
    .... etc

Reference :

RunWorkerCompletedEventArgs.Result Property : MSDN

DoWorkEventArgs.Result Property : MSDN

Problem

How do I pass a value from `BackgroundWorker` `DoWork` to `BackgroundWorker` `Completed`? Since `BackgroundWorker` `Completed` is not called by `BackgroundWorker` `DoWork` I am not sure how to do this except declare a `public variable`. Essentially, I want `BackgroundWorker` `Completed` to accept through `ByVal` a variable from `BackgroundWorker` `DoWork`.

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