/// <summary>
/// This method should be called when typeinfo is not available for an object. The function
/// will check if the typeinfo is expected to be missing. This can include error cases where
/// the same error is guaranteed to happen all the time, on all machines, under all circumstances.
/// In such cases, we just have to operate without the typeinfo.
///
/// However, if accessing the typeinfo is failing in a transient way, we might want to throw
/// an exception so that we will eagerly predictably indicate the problem.
/// </summary>
private static void CheckIfMissingTypeInfoIsExpected(int hresult, bool throwIfMissingExpectedTypeInfo)
{
Debug.Assert(!ComHresults.IsSuccess(hresult));
// Word.Basic always returns this because of an incorrect implementation of IDispatch.GetTypeInfo
// Any implementation that returns E_NOINTERFACE is likely to do so in all environments
if (hresult == ComHresults.E_NOINTERFACE)
{
return;
}
// This assert is potentially over-restrictive since COM components can behave in quite unexpected ways.
// However, asserting the common expected cases ensures that we find out about the unexpected scenarios, and
// can investigate the scenarios to ensure that there is no bug in our own code.
Debug.Assert(hresult == ComHresults.TYPE_E_LIBNOTREGISTERED);
if (throwIfMissingExpectedTypeInfo)
{
Marshal.ThrowExceptionForHR(hresult);
}
}
/// <summary>
/// Look for typeinfo using IDispatch.GetTypeInfo
/// </summary>
/// <param name="dispatch"></param>
/// <param name="throwIfMissingExpectedTypeInfo">
/// Some COM objects just dont expose typeinfo. In these cases, this method will return null.
/// Some COM objects do intend to expose typeinfo, but may not be able to do so if the type-library is not properly
/// registered. This will be considered as acceptable or as an error condition depending on throwIfMissingExpectedTypeInfo</param>
/// <returns></returns>
internal static ComTypes.ITypeInfo GetITypeInfoFromIDispatch(IDispatch dispatch, bool throwIfMissingExpectedTypeInfo)
{
uint typeCount;
int hresult = dispatch.TryGetTypeInfoCount(out typeCount);
Marshal.ThrowExceptionForHR(hresult);
Debug.Assert(typeCount <= 1);
if (typeCount == 0)
{
return(null);
}
IntPtr typeInfoPtr = IntPtr.Zero;
hresult = dispatch.TryGetTypeInfo(0, 0, out typeInfoPtr);
if (!ComHresults.IsSuccess(hresult))
{
CheckIfMissingTypeInfoIsExpected(hresult, throwIfMissingExpectedTypeInfo);
return(null);
}
if (typeInfoPtr == IntPtr.Zero) // be defensive against components that return IntPtr.Zero
{
if (throwIfMissingExpectedTypeInfo)
{
Marshal.ThrowExceptionForHR(ComHresults.E_FAIL);
}
return(null);
}
ComTypes.ITypeInfo typeInfo = null;
try {
typeInfo = Marshal.GetObjectForIUnknown(typeInfoPtr) as ComTypes.ITypeInfo;
} finally {
Marshal.Release(typeInfoPtr);
}
return(typeInfo);
}
public static void CheckThrowException(int hresult, ref ExcepInfo excepInfo, uint argErr, string message)
{
if (ComHresults.IsSuccess(hresult))
{
return;
}
switch (hresult)
{
case ComHresults.DISP_E_BADPARAMCOUNT:
// The number of elements provided to DISPPARAMS is different from the number of arguments
// accepted by the method or property.
throw Error.DispBadParamCount(message);
case ComHresults.DISP_E_BADVARTYPE:
//One of the arguments in rgvarg is not a valid variant type.
break;
case ComHresults.DISP_E_EXCEPTION:
// The application needs to raise an exception. In this case, the structure passed in pExcepInfo
// should be filled in.
throw excepInfo.GetException();
case ComHresults.DISP_E_MEMBERNOTFOUND:
// The requested member does not exist, or the call to Invoke tried to set the value of a
// read-only property.
throw Error.DispMemberNotFound(message);
case ComHresults.DISP_E_NONAMEDARGS:
// This implementation of IDispatch does not support named arguments.
throw Error.DispNoNamedArgs(message);
case ComHresults.DISP_E_OVERFLOW:
// One of the arguments in rgvarg could not be coerced to the specified type.
throw Error.DispOverflow(message);
case ComHresults.DISP_E_PARAMNOTFOUND:
// One of the parameter DISPIDs does not correspond to a parameter on the method. In this case,
// puArgErr should be set to the first argument that contains the error.
break;
case ComHresults.DISP_E_TYPEMISMATCH:
// One or more of the arguments could not be coerced. The index within rgvarg of the first
// parameter with the incorrect type is returned in the puArgErr parameter.
throw Error.DispTypeMismatch(argErr, message);
case ComHresults.DISP_E_UNKNOWNINTERFACE:
// The interface identifier passed in riid is not IID_NULL.
break;
case ComHresults.DISP_E_UNKNOWNLCID:
// The member being invoked interprets string arguments according to the LCID, and the
// LCID is not recognized.
break;
case ComHresults.DISP_E_PARAMNOTOPTIONAL:
// A required parameter was omitted.
throw Error.DispParamNotOptional(message);
}
Marshal.ThrowExceptionForHR(hresult);
}
