/// <summary>
/// Convert input args into a contiguous array of real COM VARIANTs for the DISPPARAMS struct used by IDispatch::Invoke
/// see https://msdn.microsoft.com/en-us/library/windows/desktop/ms221416(v=vs.85).aspx
/// </summary>
/// <param name="args">An array of arguments to wrap</param>
/// <returns><see cref="ComTypes.DISPPARAMS"/> structure ready to pass to IDispatch::Invoke</returns>
private static ComTypes.DISPPARAMS PrepareDispatchArgs(object[] args)
{
var pDispParams = new ComTypes.DISPPARAMS();
if ((args != null) && (args.Length != 0))
{
var variantStructSize = RdMarshal.SizeOf(typeof(VARIANT));
pDispParams.cArgs = args.Length;
var argsVariantLength = variantStructSize * pDispParams.cArgs;
var variantArgsArray = RdMarshal.AllocHGlobal(argsVariantLength);
// In IDispatch::Invoke, arguments are passed in reverse order
var variantArgsArrayOffset = variantArgsArray + argsVariantLength;
foreach (var arg in args)
{
variantArgsArrayOffset -= variantStructSize;
RdMarshal.GetNativeVariantForObject(arg, variantArgsArrayOffset);
}
pDispParams.rgvarg = variantArgsArray;
}
return(pDispParams);
}