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delphiactivex

How expose the properties of a component created in an ActiveX form?

Can you publish the properties of a control that is inside an ActiveX form?

Example: I have a form with an TADOConnection component. I wish that the properties of this component can be modified by the user when he loads my ActiveX control.

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UPDATE

@TOndrej gives me a very nice sample, but this sample only works for components derived from an ActiveX control. How can I accomplish this same effect with a VCL component like a TImage or TMemo? Is it possible to publish all the properties without rewriting each property to expose them manually?

Solution

  • ADO components are already ActiveX objects, so the easiest way is to expose the connection as a simple property of your ActiveX form:

    In the type library editor, add "Microsoft ActiveX Data Objects 2.1 Library" to the list of used libraries. This will generate ADODB_TLB.pas unit in your project directory.

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    Then you can declare a new read-only property Connection of type Connection (this type is declared in ADODB_TLB unit) in your IActiveFormX interface.

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    In the implementation, you can simply return the interface from your TADOConnection component:

    type
  THackADOConnection = class(TADOConnection);

function TActiveFormX.Get_Connection: Connection;
begin
  Result := Connection(THackADOConnection(ADOConnection).ConnectionObject);
end;

    The THackADOConnection typecast is only necessary because ConnectionObject is protected. The outer Connection typecast is there to get rid of the compiler error "Incompatible types: ADODB_TLB._Connection and ADOInt._Connection."