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DllImportAttribute.PreserveSig vs PreserveSigAttribute

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DllImportAttribute.PreserveSig -

  • Mainly used in PInvoke Signatures
  • By default, while using DllImportAttribute to p-invoke, the DllImportAttribute.PreserveSig is set to true.
  • If false: Converts returned HRESULTS from unmanaged signature to managed exceptions if they are not S_OK.
  • If true: Does not convert returned HRESULT to exceptions.

   

PreserveSigAttribute (pseudo custom attribute)–

  • This is mainly used in COM interface definitions in managed code.
  • By default, for COM interface methods, the CLR does HRESULT to exception transformations (opposite behavior to that of pinvoke).
  • If attribute applied: Does not convert returned HRESULT to exceptions.
  • If attribute not applied: Default behavior of HRESULT to exception transformations.

My short-term memory is bad and I tend to forget things as soon as I learn them. So I jotted this down while I was reading Adam Nathan's excellent manuscript on COM interop. Hope you find this tidbit useful as well.