Question

I am trying to make a tabbed browser code sample, but I am having trouble implmeneting the solution correctly. I have created a custom class BrowserItem which has two values, my custom web browser and a url string. I then created an ObservableCollection of type BrowserItem, in which I add new items to the ObservableCollection on a click event. For some reason though, when I call my ShowTab method in my MainPage to show the web browser instance that the user selects (from a ListBox populated by the ObservableCollection), I am getting an ArgumentOutOfRange exception. To illustrate, what I have so far is as follows:

BrowserItem.cs

public FullWebBrowser browser
    {
        get;
        set;
    }

    public string url
    {
        get;
        set;
    }  

Settings.cs

public static Setting<ObservableCollection<BrowserItem>> Browsers = new Setting<ObservableCollection<BrowserItem>>("Browsers", new ObservableCollection<BrowserItem>());

Where the Setting class above saves and gets the ObservableCollection from isolated storage.

MainPage.xaml.cs

private void ShowTab(int index) 
    {
        this.currentIndex = index;
        //Settings.Browsers.Value.ElementAt(currentIndex);  //ArgumentOutOfRange exception
        int count = Settings.Browsers.Value.Count;

        if (count <= 0)
        {                
            FullWebBrowser browser = new FullWebBrowser();
            browser.InitialUri = "http://www.bing.com";

            BrowserItem Browser = new BrowserItem();
            Browser.browser = browser;
            Browser.url = browser.InitialUri;
            Settings.Browsers.Value.Add(Browser);
            BrowserHost.Children.Add(Browser.browser);
        }

        //SearchBar.Text = Settings.Browsers.Value.ElementAt(currentIndex).url ?? "";

        if (Settings.Browsers.Value.ElementAt(currentIndex) == null)  //ArgumentOutOfRangeException
        {
            FullWebBrowser browser = new FullWebBrowser();
            browser.InitialUri = "http://www.bing.com";

            BrowserItem Browser = new BrowserItem();
            Browser.browser = browser;
            Browser.url = browser.InitialUri;
            Settings.Browsers.Value.Add(Browser);
            BrowserHost.Children.Add(Browser.browser);
        }

        for (int i = 0; i < Settings.Browsers.Value.Count; i++)
        {
            if (Settings.Browsers.Value.ElementAt(i) != null)
            {
                Settings.Browsers.Value.ElementAt(i).browser.Visibility = i == this.currentIndex ? Visibility.Visible : Visibility.Collapsed;
            }
        }
    }

The ArgumentOutOfRangeException first occurs on Settings.Browsers.Value.ElementAt(currentIndex); in the ShowTab method, and everywhere else containing the same statement. I would just like to show the webbrowser of the corresponding index value in the ObservableCollection in MainPage.

Answer 1

You need to add items to the collection somehow from somewhere. There should be some code like

 Settings.Browsers.Value.Add(browserItemInstanceHere);

OR

 Settings.Browsers.Value = getSomeBrowserCollections();

You cannot get item from an empty collection and you index must not be greater than Count-1