Question

Edit for better understanding…

I have a Form1.cs file and a separate Class.cs file.

In Form1 I have a bgWorker that calls Class.myFunc(), this does three foreach loops, each loop return some values such as string ClientName, or string ClientOrder.

I want to return these values from Class.myFunc to bgWorker (which is inside Form1, remember) and insert them into a ListView, Textbox, or whatever.

So the problem is: How I return string values from Class.myFunc to BgWorker?

I hope someone can help me with this…

Form1.cs

void bgWorker_DoWork(object sender, DoWorkEventArgs e)
{
    ControlsHelper.ControlInvike(listProcess, () => listProcess.Items.Add("Current").Name = "item1");
            myOtherClass cp = new myOtherClass();
            cp.myFunc();
}

Class.cs

public void myFunc()
{
    foreach (string Client in Clients)
    {
           // Do something
           // Return Client and insert into listview, richtextbox, W/E
    }
} 

Answer 1

To expand on Daniel Hilgarth’s answer: if the BGW doesn’t exist in the context of Class.cs can you not pass it in as a parameter so that you can update your progress. In your DoWork signature the object sender is the BGW you want to cast as BackgroundWorker to send into myFunc.

So you’d have

public void myFunc(BackgroundWorker bgw)
{
    foreach (string Client in Clients)
    {
       // Do something
       // Return Client and insert into listview, richtextbox, W/E

       var returningObjects = List<string>();  //I assume this will be a list of strings based on your question.
       returningObjects.Add(ClientName);
       returningObjects.Add(ClientOrder);
       returningObjects.Add(Client3rdThing);

       bgw.ReportProgress(0,returningObjects)
    }
} 

An even better than using a generic List<string> you could make your own class which has all the items you need then you can call them explicitly instead of referring to a list index.

void bgWorker_DoWork(object sender, DoWorkEventArgs e)
{
    BackgroundWorker bgw = sender as BackgroundWorker;
    ControlsHelper.ControlInvike(listProcess, () => listProcess.Items.Add("Current").Name = "item1");
            myOtherClass cp = new myOtherClass();
            cp.myFunc(bgw);
}

Then in your ProgressChanged event handler

private void bgWorker_ProgressChanged(object sender,
    ProgressChangedEventArgs e)
{
   //Set the  e.UserState to whatever you need. It is of type Object.
    var returnedObjects = e.Userstate as List<string>;
    if(returnedObjects != null)
    {
        //do stuff with each of your returnedObjects[i];
    }

}

To ensure thread safety I use this extension method for controls. It’s really great having this logic wrapped up in an extension method. You don’t need to think about the Invoke structure whenever you need to call it, you just call it.

And be sure to tie it all together when you instantiate your BackgroundWorker using

bgWorker.ProgressChanged += new ProgressChangedEventHandler(bgWorker_ProgressChanged);