The query object pattern could be incorporated by introducing a query type and processing the query through the type, instead of processing it directly. Please perform the following approach we need to follow in order to incorporate the pattern in any application:
- Create a query type with the fields required for the query, as follows:
- Have a parameterized constructor that enforces the type instance to be created only if mandatory field values were provided
- The mandatory fields required for the query must be included in the constructor
Let's create a query type that filters posts by Id
; we need a query type that has an Id
field and a constructor that populates the Id
field:
public class PostDetailQuery { public PostDetailQuery(int? id) { this.Id = id; } public int? Id { get; set; } }
The query type is ready for implementation; let's proceed to the next step, creating handlers.
- Create a query handler interface...