Bot Framework code to get bytes from Attachment on Skype

gistfile1.txt

byte[] imageBytes = null;

// For Skype we need to get an OAuth token to access the content url
if (activity.ChannelId.ToLower() == "skype")
{
    using (var httpClient = new HttpClient())
    {
        // Request OAuth token
        var formValues = new KeyValuePair<string, string>[]
        {
            new KeyValuePair<string, string>("client_id", ConfigurationManager.AppSettings["MicrosoftAppId"]),
            new KeyValuePair<string, string>("client_secret", ConfigurationManager.AppSettings["MicrosoftAppPassword"]),
            new KeyValuePair<string, string>("grant_type", "client_credentials"),
            new KeyValuePair<string, string>("scope", "https://graph.microsoft.com/.default")
        };

        // Anonymous definition for return object
        var definition = new { access_token = "" };

        var tokenJson = await httpClient.PostAsync("https://login.microsoftonline.com/common/oauth2/v2.0/token",
            new FormUrlEncodedContent(formValues));

        var token = JsonConvert.DeserializeAnonymousType(await tokenJson.Content.ReadAsStringAsync(), definition);

        // Set Bearer: <token> header for the request
        httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token.access_token);
        imageBytes = await httpClient.GetByteArrayAsync(attachment.ContentUrl);
    }
}
else
    imageBytes = BotHelper.ConvertContentToByteArray(attachment.ContentUrl);