How can I add fields to a clientdataset at runtime?

Question

I have a TClientDataSet, which is provided by a TTable’s dataset. The dataset has two fields: postalcode (string, 5) and street (string, 20)

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Answer 1

if you want to combine already existing "dynamic" data fields (from provider side) with additional client side persistent fields (calculated, lookup, internalcalc, aggregate) you should subclass CDS. just introduce extra boolean property CombineFields and either override BindFields (in newer delphi versions) or the entire InternalOpen (as I did in d2006/2007) with the following line

if DefaultFields or CombineFields then CreateFields; { TODO -ovavan -cSIC : if CombineFields is true then persistent fields will coexist with Default ones }

that will allow you to avoid all that runtime mess with FieldDefs/CreateField