Searches and Pagination

An extremely common use case in applications is the need to search for entities and display them in a paginated list. Greyhound provides a SearchResult<T> class and a Pagination class to support this use case.

SearchResult

The SearchResult<T> class is a generic class that contains a collection of entities of type T, as well as pagination information. It is designed to be used as the return type for search requests.

The recommended way to construct a SearchResult<T> is to use the constructor with three arguments: the collection of entities, the requested pagination, and the total count of entities. The pagination information should be a Pagination object, typically passed in from the request.

Tip

Pagination includes a Pagination.Zero instance that can be used to indicate to the handler that no actual page of results is needed. This is useful when you only need the total count of entities. When writing a search handler, be sure to support this case.

public async Task<Response<SearchResult<Employee>>> Handle(SearchEmployeesRequest request, CancellationToken cancellationToken)
{
  // Count the total number of employees matching the criteria
  int totalCount = await CountEmployees(request, cancellationToken);

  // Handle Pagination.Zero
  if (request.Pagination.PageSize == 0)
  {
    return new SearchResult<Employee>([], request.Pagination, totalCount);
  }

  // Perform the search
  List<Employee> employees = await SearchForEmployees(request, cancellationToken);

  // Construct the search result
  return new SearchResult<Employee>(employees, request.Pagination, totalCount);
}

Pagination

The Pagination type represents the pagination information for a search request. At minimum, it includes the page number and size. The Pagination type is designed to be passed in from the request and used to limit the number of entities returned. A Pagination object can also be constructed with a total count of entities to support pagination controls in the UI.