c# - How do I handle var (or ref) parameters in COM Interop? -


i have stand-alone application exposes com interfaces/coclasses/enums, etc. 1 of interfaces exports following function:

procedure findtask(const taskid: widestring; var task: olevariant); safecall;

note: task exposed coclass.
note: task [in, out]

so far, legacy application, written in delphi, had been able communicate stand-alone application. consider stand-alone app out-of-proc com server , consider legacy app client app.

as rewriting old delphi app (client) in c#, have use com interop in c# communicate application. therefore, made use of tlbimp.exe translate com interfaces c# interfaces.

that method translated following:

void findtask(string, taskid, ref object task);

how can call findtask , receive result of existent task signature?

i've tried this: (task coclass type)

sctask target = new cstask(); scheduler.findtask("a guid value", ref target);

but compiler yelled type, since there no overload class type (the translated method receives object)

could this, instead?

object target = new object(); scheduler.findtask("a guid value", ref target); sctask translated = (sctask) target;

how can call method expects var (in, out) variant *, therefore translated object, have more precise type?

it rather looks me though parameter out parameter. don't appear attempting pass in. method appears returning different object. in c# ought be:

void findtask(string taskid, out object task);

you'd call this:

you'd need change type library specify out semantics.

if in/out you'd keep use of ref , call method this:

object target = null; scheduler.findtask("a guid value", ref target); sctask translated = (sctask) target;

or possibly pass in actual object meaningful state if that's how designed work.


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