/// <summary>
/// Modifies the current sort stage by appending a descending field specification to it.
/// </summary>
/// <typeparam name="TResult">The type of the result.</typeparam>
/// <param name="aggregate">The aggregate.</param>
/// <param name="field">The field to sort by.</param>
/// <returns>
/// The fluent aggregate interface.
/// </returns>
public static IOrderedAggregateFluent <TResult> ThenByDescending <TResult>(this IOrderedAggregateFluent <TResult> aggregate, Expression <Func <TResult, object> > field)
{
Ensure.IsNotNull(aggregate, "aggregate");
Ensure.IsNotNull(field, "field");
// this looks sketchy, but if we get here and this isn't true, then
// someone is being a bad citizen.
var lastStage = aggregate.Stages.Last();
aggregate.Stages.RemoveAt(aggregate.Stages.Count - 1); // remove it so we can add it back
var stage = new DelegatedPipelineStageDefinition <TResult, TResult>(
"$sort",
(s, sr) =>
{
var lastSort = lastStage.Render(s, sr).Document["$sort"].AsBsonDocument;
var newSort = new DirectionalSortDefinition <TResult>(new ExpressionFieldDefinition <TResult>(field), SortDirection.Descending).Render(s, sr);
return(new RenderedPipelineStageDefinition <TResult>("$sort", new BsonDocument("$sort", lastSort.Merge(newSort)), s));
});
return((IOrderedAggregateFluent <TResult>)aggregate.AppendStage(stage));
}
Order <T>(IOrderedAggregateFluent <T> source)
{
return(source.ThenByDescending(Property.QueryFrom <T>()));
}
/// <summary>
/// Modifies the current sort stage by appending a descending field specification to it.
/// </summary>
/// <typeparam name="TResult">The type of the result.</typeparam>
/// <param name="aggregate">The aggregate.</param>
/// <param name="field">The field to sort by.</param>
/// <returns>
/// The fluent aggregate interface.
/// </returns>
public static IOrderedAggregateFluent <TResult> ThenByDescending <TResult>(this IOrderedAggregateFluent <TResult> aggregate, Expression <Func <TResult, object> > field)
{
Ensure.IsNotNull(aggregate, nameof(aggregate));
return(aggregate.ThenBy(Builders <TResult> .Sort.Descending(field)));
}
/// <summary>
/// Modifies the current sort stage by appending a descending field specification to it.
/// </summary>
/// <typeparam name="TDocument">The type of the document.</typeparam>
/// <typeparam name="TResult">The type of the result.</typeparam>
/// <param name="source">The source.</param>
/// <param name="field">The field to sort by.</param>
/// <returns>The fluent aggregate interface.</returns>
public static IOrderedAggregateFluent <TDocument, TResult> ThenByDescending <TDocument, TResult>(this IOrderedAggregateFluent <TDocument, TResult> source, Expression <Func <TResult, object> > field)
{
Ensure.IsNotNull(source, "source");
Ensure.IsNotNull(field, "field");
var helper = new BsonSerializationInfoHelper();
helper.RegisterExpressionSerializer(field.Parameters[0], source.Collection.Settings.SerializerRegistry.GetSerializer <TResult>());
var sortDocument = new SortByBuilder <TResult>(helper).Descending(field).ToBsonDocument();
// this looks sketchy, but if we get here and this isn't true, then
// someone is being a bad citizen.
var currentSortStage = (BsonDocument)source.Pipeline.Last();
currentSortStage["$sort"].AsBsonDocument.AddRange(sortDocument);
return(source);
}
