How to get the value of a returned value from an async from an external function in PowerBuilder?

Question

How to get the value of a returned value from an async from an external function in PowerBuilder? I made a simple example in VB2013 .NET 4.5 and compiled it as a DLL. And inside the DLL is an async method like so:

test.DLL

    public async Task<string> GetTestAsync()
    {
        Task<string> task = GetTest();

        string test = await task;

        return test;
    }

    public async Task<string> GetTest()
    {
        string test;
        test = "TEST";

        return test;
    }

and I have called the DLL in PowerBuilder like so:

String test
test = String(myoleobject.GetPortsTestAsync())

if isnull(test) then
   messagebox('', 'null value')
end if

The result always returns a null value.

I've also tried this one, but it still returns a null value.

    public Task<string> GetTestAsync()
    {
        return Task.Factory.StartNew(() =>
        {
            return "hello";
        });
    }

score 0 · Answer 1 · answered Dec 05 '19 at 12:57

You'll need to perform a callback from your DLL to PowerBuilder.

I assume that because you call a method of "myoleobject" that you are using oleobject.

If that is the case, here is something to try.

In VB

Create an OLE event
Set the value
Trigger the event

In PowerBuilder

Inherit an OLEOBJECT
Create an event that corresponds to the VB OLE event
Get the value.

score -1 · Answer 2 · answered Mar 18 '16 at 09:17

You might need to get creative here, the only thing that jumps out at me is to set a property in your VB control that informs your PB application that a value is ready. The problem is that you are forced to poll the VB application constantly.

Another option is to hold-up PB when the function is called in VB, but it totally defeats the purpose of an async function. Wish I could help more been a while since I've done anything like this.

How to get the value of a returned value from an async from an external function in PowerBuilder?

2 Answers2