<PackageReference Include="System.Reactive" Version="4.2.0-preview.625" />

LocalQueryMethodImplementationTypeAttribute

Attribute applied to static classes providing expression tree forms of query methods, mapping those to the corresponding methods for local query execution on the specified target class type.
public Type TargetType { get; }

Gets the type with the implementation of local query methods.

Creates a new mapping to the specified local execution query method implementation type.