GetStats - a function that retrieves data from the SendGrid Web API stats endpoint from within a Windows Phone 8.1 app

GetStats-WindowsPhone-SendGrid.cs

public async Task<ObservableCollection<EmailStats>> GetStats(uint days = 1, uint aggregate = 0)
{
	if (days < 1)
		throw new ArgumentException("The days argument must be larger than 0.", "days");
	if (days > 1095)
		throw new ArgumentException("The days argument must be less than 1096.", "days");

	var httpClient = new HttpClient();
	var response = await httpClient.GetAsync(
		new Uri(String.Format("{0}stats.get.json?api_user={1}&api_key={2}&date=1&days={3}&aggregate={4}", 
			SendGridApiBase, SendGridUsername, SendGridPassword, days, aggregate)));
    		
    	string responseBody = await response.Content.ReadAsStringAsync();
    		
    	if (aggregate == 1)
        	responseBody = "[" + responseBody + "]";
    		
    	return  JsonConvert.DeserializeObject<ObservableCollection<EmailStats>>(responseBody);
}