C# 3.0 Cookbook

Recipe 5.9 Handling User -Defined HRESULTs

Problem

A COM object can return a user-defined HRESULT or an HRESULT that has no mapping to a managed exception type. You wish to handle these returned HRESULT s in a more specific manner.

Solution

The following code fragment illustrates the handling of user-defined COM/COM+ exceptions:

try { CallCOMMethod( ); } catch (System.Runtime.InteropServices.COMException ce) { switch ((uint)ce.ErrorCode) { case 0x80132000: // Handle this specific user-defined COM/COM+ exceptions here break; case 0x80132001: // Handle this specific user-defined COM/COM+ exceptions here break; default: // Handle any other specific user-defined COM/COM+ // exceptions here break; } } catch (Exception e) { // Handle all other exceptions here }

Discussion

Handle any user-defined exceptions that are unique to a specific COM/COM+ component by trapping the COMException exception. This class reflects COM/COM+ HRESULT s that have no mapping to managed exceptions.

The COMException has a property, ErrorCode , in addition to those properties in the base Exception class. This property contains the HRESULT value that the COM/COM+ object returned. Another difference between COMException and Exception is that the InnerException property of a COMException object will always be null .

See Also

See the "Error Raising and Handling Guidelines" and "Handling COM Interop Exceptions" topics in the MSDN documentation.