How to access document attachments from hierarchical transformation

Question

My site has this structure:

Products
    category 1
        item 1
            item 1 attachments
    category 2
        item 2
            item 2 attachments

I have successfully written a hierarchical transformation that shows the data on the page at the top level. I cannot for the life of me figure out how to access the attachments for each document though.

Anyone have any idea?

Answer 1

I suppose you mean unsorted attachments you add in Properties -> Attachments section. In this case yuo can register following control in your transformation:

<%@ Register Src="~/CMSInlineControls/DocumentAttachments.ascx" TagName="DocumentAttachments" TagPrefix="cms" %>

And use it like this:

<cms:DocumentAttachments ID="ucDocAttachments" runat="server" TransformationName="cms.root.attachment" Path='<%# Eval("NodeAliasPath") %>' />

Answer 2

If you are talking about Group attachments (this is when you have a field in your page type using the Attachments data type) then in order to access the attachments inside your transformation you need to write either a custom macro (when using Text/XML transformation) or custom transformation method. Both can be done very easily. The code itself that gets you the attachments can be like this:

public ObjectQuery<AttachmentInfo> GetAttachmentsFromField(string className, int documentID, string attachmentColumnName)
{
    // get class info       
    var classInfo = new FormInfo(DataClassInfoProvider.GetDataClassInfo(className).ClassFormDefinition);
    if (classInfo != null)
    {
        // get attachment field definition            
        var attachmentsField = classInfo.GetFormField(attachmentColumnName);
        if (attachmentsField != null)
        {
            // get attachments strored in the field by GUID
            var attachments = AttachmentInfoProvider.GetAttachments()
                .WhereEquals("3CCC6E6C-56F3-42EB-8385-979973D99C55", attachmentsField.Guid)
                .And()
                .WhereEquals("AttachmentDocumentID", documentID);

            return attachments;
        }
    }
    return null;
}

With this it is very important to take into account that this code introduces several other SQL queries against database and therefore it should be optimized by using caching appropriately.

Answer 3

I wrote a pretty detailed blog post on this a while back. It describes very similar attributes to Enn's answer but gives great detail on why you do specific things.