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PipelineDefinitionBuilderLookupTInput, TIntermediate, TForeignDocument, TAsElement, TAs, TOutput Method (PipelineDefinitionTInput, TIntermediate, IMongoCollectionTForeignDocument, BsonDocument, PipelineDefinitionTForeignDocument, TAsElement, ExpressionFuncTOutput, TAs, AggregateLookupOptionsTForeignDocument, TOutput)

Appends a $lookup stage to the pipeline.

Namespace:  MongoDB.Driver
Assembly:  MongoDB.Driver (in MongoDB.Driver.dll) Version: 2.18.0+554c799eb1ec8dd732f16c739387f6664df1ba7a
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,
	Expression<Func<TOutput, TAs>> as,
	AggregateLookupOptions<TForeignDocument, TOutput> options = null
)
where TAs : Object, IEnumerable<TAsElement>

Parameters

pipeline
Type: MongoDB.DriverPipelineDefinitionTInput, TIntermediate
The pipeline.
foreignCollection
Type: MongoDB.DriverIMongoCollectionTForeignDocument
The foreign collection.
let
Type: MongoDB.BsonBsonDocument
The "let" definition.
lookupPipeline
Type: MongoDB.DriverPipelineDefinitionTForeignDocument, TAsElement
The lookup pipeline.
as
Type: System.Linq.ExpressionsExpressionFuncTOutput, TAs
The as field in TOutput in which to place the results of the lookup pipeline.
options (Optional)
Type: MongoDB.DriverAggregateLookupOptionsTForeignDocument, 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: PipelineDefinitionTInput, TOutput
The stage.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type PipelineDefinitionTInput, 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