| PipelineDefinitionBuilderLookupTInput, TIntermediate, TForeignDocument, TOutput Method (PipelineDefinitionTInput, TIntermediate, IMongoCollectionTForeignDocument, ExpressionFuncTIntermediate, Object, ExpressionFuncTForeignDocument, Object, ExpressionFuncTOutput, Object, AggregateLookupOptionsTForeignDocument, TOutput) | 
 
            Appends a lookup stage to the pipeline.
            
 
    Namespace: 
   MongoDB.Driver
    Assembly:
   MongoDB.Driver (in MongoDB.Driver.dll) Version: 2.12.2+a4a3888f4fb51bb518b1eb5002effc2d47f2ea6a
 Syntax
Syntaxpublic 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
)
<ExtensionAttribute>
Public Shared Function Lookup(Of TInput, TIntermediate, TForeignDocument, TOutput) ( 
	pipeline As PipelineDefinition(Of TInput, TIntermediate),
	foreignCollection As IMongoCollection(Of TForeignDocument),
	localField As Expression(Of Func(Of TIntermediate, Object)),
	foreignField As Expression(Of Func(Of TForeignDocument, Object)),
	as As Expression(Of Func(Of TOutput, Object)),
	Optional options As AggregateLookupOptions(Of TForeignDocument, TOutput) = Nothing
) As PipelineDefinition(Of TInput, TOutput)
[<ExtensionAttribute>]
static member Lookup : 
        pipeline : PipelineDefinition<'TInput, 'TIntermediate> * 
        foreignCollection : IMongoCollection<'TForeignDocument> * 
        localField : Expression<Func<'TIntermediate, Object>> * 
        foreignField : Expression<Func<'TForeignDocument, Object>> * 
        as : Expression<Func<'TOutput, Object>> * 
        ?options : AggregateLookupOptions<'TForeignDocument, 'TOutput> 
(* Defaults:
        let _options = defaultArg options null
*)
-> PipelineDefinition<'TInput, 'TOutput> 
Parameters
- pipeline
- Type: MongoDB.DriverPipelineDefinitionTInput, TIntermediate
 The pipeline.
- foreignCollection
- Type: MongoDB.DriverIMongoCollectionTForeignDocument
 The foreign collection.
- localField
- Type: System.Linq.ExpressionsExpressionFuncTIntermediate, Object
 The local field.
- foreignField
- Type: System.Linq.ExpressionsExpressionFuncTForeignDocument, Object
 The foreign field.
- as
- Type: System.Linq.ExpressionsExpressionFuncTOutput, Object
 The "as" field.
- 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.
- TOutput
- The type of the output documents.
Return Value
Type: 
PipelineDefinitionTInput, 
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 
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
See Also