Question

I try to use data after I downloaded it from an API. Example of my code:

private int id;
public MainPage()
{
    InitializeComponent();
    SomeFunction();
}
public void SomeFunction()
{
    DownloadFromAPI("url to api");
    MessageBox.Show(id.ToString());  //<< Returns 0
}
public void DownloadFromAPI(DownloadStringCompletedEventArgs url)
{
    //code to retrieve data (singel id)
    id = Int16.Parse(data);
    MessageBox.Show(id.ToString());  //<< Returns the correct number, like 14
    test();
}
private void test()
{
    MessageBox.Show(id.ToString());  //<< Even Returns the correct number 14 
}

How is it possible to load the id information after DownloadFromAPI("url to api"); is finished. so i get the right number (14) instead of 0?

Answer 1

I suspect your method actually looks like this:

public void DownloadFromAPI(...)
{
    int id = Int16.Parse(data);
    MessageBox.Show(id.ToString());  //<< Returns the correct number, like 14
}

That’s declaring a new local variable within the method, rather than assigning a value to the instance variable.

However, personally, I’d often prefer to write the method to return the value instead:

public int DownloadFromApi(...)
{
    return Int16.Parse(data);
}

Of course if this really is natural state within the object, it may make sense – but often it can be simpler to write code which just computes a value and returns it, than getting into mutation territory.