public SerializationExpression BindProjector(ref Expression selector)
{
var projector = selector as SerializationExpression;
if (selector.NodeType == ExpressionType.MemberInit || selector.NodeType == ExpressionType.New)
{
var serializer = SerializerBuilder.Build(selector, _serializerRegistry);
projector = new DocumentExpression(serializer);
}
else if (projector == null || projector is PipelineExpression || projector is IFieldExpression || projector is ArrayIndexExpression)
{
var newFieldName = "__fld0";
if (projector is IFieldExpression)
{
// We don't have to do this, but it makes the output a little nicer.
newFieldName = ((IFieldExpression)projector).FieldName;
}
// the output of a $project stage must be a document, so
// if this isn't already a serialization expression and it's not
// a new expression or member init, then we need to create an
// artificial field to project the computation into.
var serializer = GetSerializer(selector.Type, selector);
selector = new FieldAsDocumentExpression(selector, newFieldName, serializer);
projector = new FieldExpression(newFieldName, serializer);
}
return(projector);
}
protected internal override Expression VisitDocumentWrappedField(FieldAsDocumentExpression node)
{
var field = Visit(node.Document) as IFieldExpression;
if (field != null)
{
return(new FieldExpression(
node.PrependFieldName(field.FieldName),
node.Serializer));
}
return(node);
}
private BsonValue TranslateDocumentWrappedField(FieldAsDocumentExpression expression)
{
return(new BsonDocument(expression.FieldName, TranslateValue(expression.Expression)));
}
