private void Detail1_BeforePrint(object sender, System.Drawing.Printing.PrintEventArgs e) {
    pictureBox1.ImageUrl = "http://YourNoImageAvailableURLGoesHere.jpg";
    var serviceUrl = "https://YourMapServiceURLGoesHere/MapServer/0/";
    var fid = GetCurrentColumnValue("OBJECTID");
    
    var attachmentsUrl = serviceUrl + fid + "/attachments?f=json";
    using (var wc = new System.Net.WebClient())
    {
        using (var stream = wc.OpenRead(attachmentsUrl))
        {
            var serializer = new Newtonsoft.Json.JsonSerializer();
            using (var sr = new System.IO.StreamReader(stream))
            using (var jsonTextReader = new Newtonsoft.Json.JsonTextReader(sr))
            {
                var response = serializer.Deserialize<Newtonsoft.Json.Linq.JObject>(jsonTextReader);
                var infos = response["attachmentInfos"] as Newtonsoft.Json.Linq.JArray;
                if (infos != null)
                {
                    var info = System.Linq.Enumerable.FirstOrDefault(infos, (x) =>
                    {
                        var contentType = (string)x["contentType"];
                        if (!string.IsNullOrEmpty(contentType) && contentType.StartsWith("image/"))
                        {
                            return true;
                        }
                        return false;
                    });
                    if (info != null)
                    {
                        var imageUrl = serviceUrl + fid + "/attachments/" + info["id"].ToString();
                        pictureBox1.ImageUrl = imageUrl;
                        pictureBox1.Visible = true;
                    }
                }
            }
        }
    }
}