Accessing feature attachments using ArcObjects?

Question

I am attempting to access a feature's attachments in ArcObjects and I'm following the docs for Working with feature attachments. Everything is fine until attempt to access IAttachment.Data because I am expecting there to be data, but that property is null:

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which means I can't proceed past: IMemoryBlobStream memoryBlobStream = attachment.Data;

I am thinking there is a missing step (or steps) in the docs that would fill the attachment object's Data property with actual data? How is this done?

I am able to access the attachment via the Identify window within ArcMap, so I know the data is there:

enter image description here

JC5577 · Accepted Answer · 2014-09-12 16:54:31Z

The issue was a combination of me copying the wrong snippet of code and not fully reading the docs that I had referenced in my question!

The Boolean parameter ("Info Only") of these methods determines which properties of the returned attachments will be populated.

I had copied:

IEnumAttachment enumAttachment = attachmentManager.GetAttachmentsByParentIDs (parentIdArray, true);

Changing it to false brings brings back the .Data value:

IEnumAttachment enumAttachment = attachmentManager.GetAttachmentsByParentIDs (parentIdArray, false);

Both lines of code are present in the docs.

Hornbydd · Accepted Answer · 2014-09-12 17:48:19Z

I have never done this using the .NET SDK, but I have used this python script in the past:

import arcpy, os, sys
arcpy.env.overwriteOutput = True

def extract_attachments(out_ws, table, blob_field, filename_fld):
    '''
    Code adopted from "Another GIS Blog"
        http://anothergisblog.blogspot.nl/2012/06/working-with-blob-data-at-101-arcpyda.html

    """ Exports all attachments from a geodatabase to a new location """

    Required:
    out_ws -- location for attachments
    table -- table or feature class containing attachment info
    blob_field -- field containing attachment files
    filename_fld -- field name containing file name
    '''

    # make sure out_ws exists, if not create
    if not os.path.exists(out_ws):
        os.makedirs(out_ws)

    # search cursor
    c = 0
    with arcpy.da.SearchCursor(table, ['REL_OBJECTID', blob_field, filename_fld]) as rows:
        for row in rows:
            roid, binRep, fileName = row
            if binRep:
                out_file = os.path.join(out_ws, 'OID_' + '_'.join(map(str, [roid, fileName])))
                open(out_file, 'wb').write(binRep.tobytes())
                c += 1

    arcpy.AddMessage('Exported {0} attachments to: "{1}"'.format(c, out_ws))
    return

if __name__ == '__main__':

    # run as script tool
    extract_attachments(*sys.argv[1:])

Does this have to be done in ArcObjects?

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