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PipelineDefinitionBuilder.Lookup<TInput, TIntermediate, TForeignDocument, TOutput> Method (PipelineDefinition<TInput, TIntermediate>, IMongoCollection<TForeignDocument>, Expression<Func<TIntermediate, Object>>, Expression<Func<TForeignDocument, Object>>, Expression<Func<TOutput, Object>>, AggregateLookupOptions<TForeignDocument, TOutput>)

Appends a lookup stage to the pipeline.

Namespace:  MongoDB.Driver
Assembly:  MongoDB.Driver (in MongoDB.Driver.dll) Version: 2.6.0+Branch.origin/v2.6.x.Sha.593796a7b35dc59243383bcc684de296a5468f2e
Syntax
public static PipelineDefinition<TInput, TOutput> Lookup<TInput, TIntermediate, TForeignDocument, TOutput>(
	this PipelineDefinition<TInput, TIntermediate> pipeline,
	IMongoCollection<TForeignDocument> foreignCollection,
	Expression<Func<TIntermediate, Object>> localField,
	Expression<Func<TForeignDocument, Object>> foreignField,
	Expression<Func<TOutput, Object>> as,
	AggregateLookupOptions<TForeignDocument, TOutput> options = null
)

Parameters

pipeline
Type: MongoDB.Driver.PipelineDefinition<TInput, TIntermediate>
The pipeline.
foreignCollection
Type: MongoDB.Driver.IMongoCollection<TForeignDocument>
The foreign collection.
localField
Type: System.Linq.Expressions.Expression<Func<TIntermediate, Object>>
The local field.
foreignField
Type: System.Linq.Expressions.Expression<Func<TForeignDocument, Object>>
The foreign field.
as
Type: System.Linq.Expressions.Expression<Func<TOutput, Object>>
The "as" field.
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.
TOutput
The type of the output documents.

Return Value

Type: PipelineDefinition<TInput, TOutput>
The fluent aggregate interface.

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