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MS Access and tryingto detect Null blobs using TBlobField.IsNull method

I have an MS Access table with blob fields in it. When I use the TBlobField.IsNull method it always returns True whether the blob field has data or is Null. This same test works fine with Paradox and if do a query against the MS access table to look for null blobs (for example select * from blobtest where blob IS NULL) it detects and shows the records with empty blobs correctly. What is wrong and how can I work around it?

The DAO engine does not know without opening the Blob if it is null or not. The BDE would have to open the all the Blob fields at every getrecord call for the TBlobField.IsNull

function to work correctly. This would be a huge performance hit even though IsNull may

never be used. A workaround is to use .AsString and check the length:

before: (assume that Table blob is a TBlobField) if Table blob .isNull then

after:

if Length(Table blob .AsString) = 0) then

3/26/99 :00:59 AM

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