/// <summary>
/// Tries to the move to the next page in the document producer.
/// </summary>
/// <param name="token">The cancellation token.</param>
/// <returns>Whether the operation was successful.</returns>
private async Task <bool> MoveNextPageAsync(CancellationToken token)
{
token.ThrowIfCancellationRequested();
if (this.itemsLeftInCurrentPage != 0)
{
throw new InvalidOperationException("Tried to move onto the next page before finishing the first page.");
}
// We need to buffer pages if empty, since that how we know there are no more pages left.
await this.BufferMoreIfEmptyAsync(token);
if (this.bufferedPages.Count == 0)
{
return(false);
}
// Pull a FeedResponse using TryMonad (we could have buffered an exception).
TryMonad <DocumentFeedResponse <CosmosElement> > tryMonad = await this.bufferedPages.TakeAsync(token);
DocumentFeedResponse <CosmosElement> feedResponse = tryMonad.Match <DocumentFeedResponse <CosmosElement> >(
onSuccess: ((page) =>
{
return(page);
}),
onError: (exceptionDispatchInfo) =>
{
exceptionDispatchInfo.Throw();
return(null);
});
// Update the state.
this.PreviousContinuationToken = this.currentContinuationToken;
this.currentContinuationToken = feedResponse.ResponseContinuation;
this.currentPage = feedResponse.GetEnumerator();
this.IsAtBeginningOfPage = true;
this.itemsLeftInCurrentPage = feedResponse.Count;
// Prime the enumerator,
// so that current is pointing to the first document instead of one before.
if (this.MoveToFirstDocumentInPage())
{
this.IsAtBeginningOfPage = true;
return(true);
}
else
{
// We got an empty page
if (this.currentContinuationToken != null)
{
return(await this.MoveNextPageAsync(token));
}
return(false);
}
}
/// <summary>
/// Tries to the move to the next page in the document producer.
/// </summary>
/// <param name="token">The cancellation token.</param>
/// <returns>Whether the operation was successful.</returns>
private async Task <bool> MoveNextPageAsync(CancellationToken token)
{
token.ThrowIfCancellationRequested();
if (this.bufferedPages.Count == 0)
{
return(false);
}
if (this.itemsLeftInCurrentPage != 0)
{
throw new InvalidOperationException("Tried to move onto the next page before finishing the first page.");
}
TryMonad <DocumentFeedResponse <CosmosElement> > tryMonad = await this.bufferedPages.TakeAsync(token);
DocumentFeedResponse <CosmosElement> feedResponse = tryMonad.Match <DocumentFeedResponse <CosmosElement> >(
onSuccess: ((page) =>
{
return(page);
}),
onError: (exceptionDispatchInfo) =>
{
exceptionDispatchInfo.Throw();
return(null);
});
this.previousContinuationToken = this.currentContinuationToken;
this.currentContinuationToken = feedResponse.ResponseContinuation;
this.currentPage = feedResponse.GetEnumerator();
this.itemsLeftInCurrentPage = feedResponse.Count;
if (this.MoveNextDocumentWithinCurrentPage())
{
this.isAtBeginningOfPage = true;
return(true);
}
else
{
return(false);
}
}