C# Async Task won't continue

Question

I have a problem. In my Xamarin Forms app I have the following code to toggle a device in my network:

public ICommand cmdTogglePower
{
    get
    {
        return new Command<int>((x) => TogglePower_Handler(x));
    }
}

public Task TogglePower_Handler(int Id)
{
    return TogglePower(Id);
}

private async Task TogglePower(int Id)
{
    foreach (var item in knownDeviceList)
    {
        if (item.Id == Id)
        {
            if (item.State == 1) { item.State = 0; }
            else if (item.State == 0) { item.State = 1; }

            switch (item.State)
            {
                case 1:
                    item.StateShown = "Turned on";
                    item.PowerStateColor = "#FFFFFF";
                    item.DeviceImageColor = item.Color;
                    break;
                case 0:
                    item.StateShown = "Turned off";
                    item.PowerStateColor = "#707070";
                    item.DeviceImageColor = "#707070";
                    break;
            }

            foreach (var device in App.KnownDeviceList)
            {
                if (device.Id == Id)
                {
                    device.State = item.State;

                    int rgb = Convert.ToInt32(item.Color, 16);
                    int r = (rgb & 0xff0000) >> 16;
                    int g = (rgb & 0xff00) >> 8;
                    int b = (rgb & 0xff);

                    string status = await App.RestService.SendCommand(r, g, b);

                    break;
                }
            }

            break;
        }
    }
}

And I want the app to call a Task SendCommand, which sends a https command over the network to that device in another class. Here is the code of that Task:

public async Task<string> SendCommand(int Red, int Green, int Blue)
{
    var postData = new List<KeyValuePair<string, string>>();
    postData.Add(new KeyValuePair<string, string>("red", Red.ToString()));
    postData.Add(new KeyValuePair<string, string>("green", Green.ToString()));
    postData.Add(new KeyValuePair<string, string>("blue", Blue.ToString()));

    var content = new FormUrlEncodedContent(postData);
    var weburl = "mysite.org";
    string response = await PostResponseSendCommand(weburl, content);

    return response;
}

public async Task<string> PostResponseSendCommand(string weburl, FormUrlEncodedContent content)
{
    var response = await client.PostAsync(weburl, content);
    var responseString = await response.Content.ReadAsStringAsync();

    return responseString;
}

But the code stops after int rgb = Convert.ToInt32(item.Color, 16); Now the Task never gets executed, so somehting is going wrong!

Why is this not working !?

Answer 1

The problem:
Your color values start with a "#", which Convert.ToInt32() can't process, it causes a System.FormatException: Could not find any recognizable digits. And that exception "disappears" because it happens inside the asynchronous state machine.

The fix:
Chop off the leading "#", e.g. like this:

int rgb = Convert.ToInt32(item.Color.Substring(1), 16);