Question

I’m coding an app for Windows 8 which needs to get the HTML of a particular site. It was working well when i coded it into the button event which is in the MainPage. However, when I tried to do it in my class ‘Band’:

        public Band(String Name)
    {
        this.Name = Name;
        GetHtmlDocument();
        GenerateId();
        GetAlbumDocument();
        GenerateLogo();
        GeneratePhoto();
        CreateAlbumList();
    }

    private async void GetHtmlDocument()
    {
        HttpClientHandler handler = new HttpClientHandler();
        HttpClient client = new HttpClient(handler as HttpMessageHandler) { BaseAddress = new Uri(@"http://www.metal-archives.com/bands/" + Name) };
        var r = await client.GetAsync(client.BaseAddress);
        string html = null;
        if (r.IsSuccessStatusCode) html = await r.Content.ReadAsStringAsync();
        HtmlAgilityPack.HtmlDocument document = new HtmlAgilityPack.HtmlDocument();
        document.LoadHtml(html);
        DocumentBand = document;
    }

It came to

var r = await client.GetAsync(client.BaseAddress);

line and then proceed from the GenerateId() method as it is in the constructor. But in order to process GenerateId() method, GetHtmlDocument() method must be finished. What should i do in this situation?

My main language is Java and I’m very new to the C#, so there may huge coding or naming mistakes.

Answer 1

I would do something like this:

    public Band(String Name)
    {
        this.Name = Name;
    }

    public async Task Init()
    {
        await GetHtmlDocument();
        GenerateId();
        GetAlbumDocument();
        GenerateLogo();
        GeneratePhoto();
        CreateAlbumList();
    }

    // Note Task Return type
    private async Task GetHtmlDocument()
    {
        HttpClientHandler handler = new HttpClientHandler();
        HttpClient client = new HttpClient(handler as HttpMessageHandler) { BaseAddress = new Uri(@"http://www.metal-archives.com/bands/" + Name) };
        var r = await client.GetAsync(client.BaseAddress);
        string html = null;
        if (r.IsSuccessStatusCode) html = await r.Content.ReadAsStringAsync();
        HtmlAgilityPack.HtmlDocument document = new HtmlAgilityPack.HtmlDocument();
        document.LoadHtml(html);
        DocumentBand = document;
    }

From your code, you would have to call init separately:

 Band band = new Band("name");
 await band.Init();

The reason for having a separate Init() function is because async and await cannot be used inside of the constructor.