How to get (download) an attachment

If you want to get an attachment from a note, then you have to get it using HTTP call. The following function returns an array of bytes that can be saved into a stream or you can convert it to Base64String (System.Convert.ToBase64String(myBytes)) if you want to save it again in CRM.

private byte[] GetAnnotationAttachment(Guid annotationId)
{
Guid attachid = annotationId;
int objecttypecode = 5; //Annotation attachment OTC
string url = _serverUrl + "Activities/Attachment/download.aspx?AttachmentType=" + objecttypecode.ToString() + "&AttachmentId=" + attachid.ToString();
System.Net.WebClient myWebClient = new System.Net.WebClient();
myWebClient.Credentials = System.Net.CredentialCache.DefaultNetworkCredentials;
return myWebClient.DownloadData(url);
}