How to Get all Replies in Discussion board using CAML

A discussion list in unlike a normal list in that it consists of two content types  - a Discussion content type that maps to the discussion topic and a Message that maps to all replies to the topic. If you examine the Discussion content type you’ll see that its inherited from the Folder content type.

The reply contains a field called ‘ParentFolderId’ and as the name suggests it holds the ID of the discussion topic. So naturally if you were to do a query on the list for all items with the same ParentFolderId you would expect the query to work. However, since the topic is of a folder content type and the replies are contained within the ‘folder’ you would need to set the  queries ViewAttributes property to "Scope='Recursive'" for it to return results.

Below is an example using the object model:

      SPQuery query = new SPQuery();

query.ViewAttributes = "Scope='Recursive'";

StringBuilder queryString = new StringBuilder();

queryString.Append("         ");

queryString.Append("              ");

queryString.Append("                        ");

queryString.Append("                             ");

queryString.Append("                             Message");

queryString.Append("                        

queryString.Append("                        ");

queryString.Append("                             ");

queryString.Append("                             99"); //NOTE: change this to the value you need

queryString.Append("                        

queryString.Append("              

queryString.Append("         

query.Query = queryString.ToString();

DataTable replyTable = discussionList.GetItems(query).GetDataTable();