Convert json string to .net object array

Your Attachment object doesn't quite reflect the data structure of the response. Create an AttachmentCollection to contain the array of attachments:

public class AttachmentCollection
{
    public List<Attachment> Attachment { get; set; }
}

Then deserialize as an AttachmentCollection:

var attachments = JsonConvert.DeserializeObject<AttachmentCollection>(content);

You can also use list(Collection) for that.

public class RootObject
{
    public List<Attachment> Attachment { get; set; }
}

You could use JSON.Net

What you need to do is first get the JSONArray and do a for statement for each JSONObject in the JSON Array. In the for statement you could use Linq to create a list of your custom Attachement class. See below:

List<Attachment> AttachmentList = new List<Attachment>();
JArray a = JArray.Parse(jsonString);

foreach (JObject o in a.Children<JObject>())
{
    Attachment newAttachment = new Attachment
    {
       WriteUpID = (int)o["WriteUpID"],
       InitialScanID = (int)o["InitialScanID"],
       //etc, do this for all Class items. 
    }
    AttachmentList.Add(newAttachment);
}
//Then change the AttachmentList to an array when you're done adding Attachments
Attachment[] attachmentArray = AttachmentList.ToArray();  

Voila