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PipelineDefinitionBuilder.Lookup<TInput, TIntermediate, TForeignDocument, TAsElement, TAs, TOutput> Method (PipelineDefinition<TInput, TIntermediate>, IMongoCollection<TForeignDocument>, BsonDocument, PipelineDefinition<TForeignDocument, TAsElement>, FieldDefinition<TOutput, TAs>, AggregateLookupOptions<TForeignDocument, TOutput>)

Appends a $lookup stage to the pipeline.

Namespace:  MongoDB.Driver
Assembly:  MongoDB.Driver (in MongoDB.Driver.dll) Version: 2.9.0+32b058abcdf2c7e8d9dd3a676d207b31897eee2e
Syntax
public static PipelineDefinition<TInput, TOutput> Lookup<TInput, TIntermediate, TForeignDocument, TAsElement, TAs, TOutput>(
	this PipelineDefinition<TInput, TIntermediate> pipeline,
	IMongoCollection<TForeignDocument> foreignCollection,
	BsonDocument let,
	PipelineDefinition<TForeignDocument, TAsElement> lookupPipeline,
	FieldDefinition<TOutput, TAs> as,
	AggregateLookupOptions<TForeignDocument, TOutput> options = null
)
where TAs : Object, IEnumerable<TAsElement>

Parameters

pipeline
Type: MongoDB.Driver.PipelineDefinition<TInput, TIntermediate>
The pipeline.
foreignCollection
Type: MongoDB.Driver.IMongoCollection<TForeignDocument>
The foreign collection.
let
Type: MongoDB.Bson.BsonDocument
The "let" definition.
lookupPipeline
Type: MongoDB.Driver.PipelineDefinition<TForeignDocument, TAsElement>
The lookup pipeline.
as
Type: MongoDB.Driver.FieldDefinition<TOutput, TAs>
The as field in TOutput in which to place the results of the lookup pipeline.
options (Optional)
Type: MongoDB.Driver.AggregateLookupOptions<TForeignDocument, TOutput>
The options.

Type Parameters

TInput
The type of the input documents.
TIntermediate
The type of the intermediate documents.
TForeignDocument
The type of the foreign collection documents.
TAsElement
The type of the as field elements.
TAs
The type of the as field.
TOutput
The type of the output documents.

Return Value

Type: PipelineDefinition<TInput, TOutput>
The stage.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type PipelineDefinition<TInput, TIntermediate>. When you use instance method syntax to call this method, omit the first parameter. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).
See Also