Count items with query using readItems(queryString) - azure-cosmosdb

Question

I want to count the number of items in a container.
Using SELECT value count(1) FROM tasks WHERE tasks.TaskState = 0 OR (tasks.TaskState = 4 AND tasks.RetryCount <= 3) works on the Azure Portal and now I want to do the same on the server side.
I tried to do this, but this don't work...
await this.Container.RetrieveItemsAsync<int>(new Query(CreateNumberOfTasksQuery()), cancellationToken: cancellationToken).ConfigureAwait(false);
And my query is:
"SELECT value count(1) FROM tasks WHERE tasks.TaskState = 0 OR (tasks.TaskState = 4 AND tasks.RetryCount <= 3)";
And I can't retrieve the item since int is not a reference type...
The implementation class:
public async Task<IList<T>> RetrieveItemsAsync<T>(Query query, QueryOptions queryOptions = null, CancellationToken cancellationToken = default)
where T : class
{
// Validation
SmartGuard.Check(() => query, typeof(T) != typeof(string), Properties.Resources.RES_Exception_MultiModel_Argument_UnsupportedType.Format(typeof(string)));
SmartGuard.NotNull(() => query, query);
// Logging
this.Service.Logger.LogDebug($"Retrieving items...");
// Delegate on instance
// Make sure the exceptions handler is called
IList<T> result = await CosmosDbMultiModelDatabaseExceptionHandler.HandleAsync(
OperationTarget.Item,
async () =>
{
IList<T> result = new List<T>();
Cosmos.FeedIterator<T> feedIterator = this.Instance.GetItemQueryIterator<T>(
queryDefinition: query.ToQueryDefinition(),
requestOptions: queryOptions.ToQueryRequestOptions());
while (feedIterator.HasMoreResults)
{
foreach (T item in await feedIterator.ReadNextAsync(cancellationToken).ConfigureAwait(false))
{
result.Add(item);
}
}
return result;
})
.ConfigureAwait(false);
// Logging
this.Service.Logger.LogDebug($"{result.Count} items were retrieved.");
// Result
return result;
}

Answer 1

This is because where T : class constraints your type must be a reference type.
You can overload your RetrieveItemsAsync method,
public async Task<IList<T>> RetrieveItemsAsync<T>(T value,Query query, QueryOptions queryOptions = null, CancellationToken cancellationToken = default)
where T : struct
{
.....
}
then you can try this:
await this.Container.RetrieveItemsAsync<int>(Int32.MaxValue,new Query(CreateNumberOfTasksQuery()), cancellationToken: cancellationToken).ConfigureAwait(false);