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IAggregateFluentExtensions.Lookup<TResult, TForeignDocument, TNewResult> Method (IAggregateFluent<TResult>, IMongoCollection<TForeignDocument>, Expression<Func<TResult, Object>>, Expression<Func<TForeignDocument, Object>>, Expression<Func<TNewResult, Object>>, AggregateLookupOptions<TForeignDocument, TNewResult>)

Appends a lookup stage to the pipeline.

Namespace:  MongoDB.Driver
Assembly:  MongoDB.Driver (in MongoDB.Driver.dll) Version: 2.21.0+5a9c3311e158910b88195f290e6d4b1b2715d2b2
Syntax
public static IAggregateFluent<TNewResult> Lookup<TResult, TForeignDocument, TNewResult>(
	this IAggregateFluent<TResult> aggregate,
	IMongoCollection<TForeignDocument> foreignCollection,
	Expression<Func<TResult, Object>> localField,
	Expression<Func<TForeignDocument, Object>> foreignField,
	Expression<Func<TNewResult, Object>> as,
	AggregateLookupOptions<TForeignDocument, TNewResult> options = null
)

Parameters

aggregate
Type: MongoDB.Driver.IAggregateFluent<TResult>
The aggregate.
foreignCollection
Type: MongoDB.Driver.IMongoCollection<TForeignDocument>
The foreign collection.
localField
Type: System.Linq.Expressions.Expression<Func<TResult, Object>>
The local field.
foreignField
Type: System.Linq.Expressions.Expression<Func<TForeignDocument, Object>>
The foreign field.
as
Type: System.Linq.Expressions.Expression<Func<TNewResult, Object>>
The field in the result to place the foreign matches.
options (Optional)
Type: MongoDB.Driver.AggregateLookupOptions<TForeignDocument, TNewResult>
The options.

Type Parameters

TResult
The type of the result.
TForeignDocument
The type of the foreign collection.
TNewResult
The type of the new result.

Return Value

Type: IAggregateFluent<TNewResult>
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 IAggregateFluent<TResult>. 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