Supplement with specific repositories for complex queries.md

https://www.perplexity.ai/search/level-layers-functionality-tec-XUGF.P3OQ222h9LUWsYxIw#3

"Supplement with specific repositories for complex queries" means that besides having a general, often generic repository for simple CRUD operations, you create specialized repository classes to handle more elaborate and performance-sensitive data retrieval needs that don't fit well into simple CRUD patterns. These specialized repositories encapsulate complex querying logic, using techniques like joins, projections, or raw SQL for efficiency.

Examples and Patterns:

1. Specific Repository for Complex Queries

   • For example, you might have a generic IRepository<T> for basic CRUD, but also an IInvoiceRepository with methods like:

     public interface IInvoiceRepository : IRepository<Invoice>
     {
         Task<IEnumerable<Invoice>> GetOverdueInvoicesAsync();
         Task<IEnumerable<Invoice>> GetCreditInvoicesAsync();
     }

   • Implementation may include optimized queries with multiple joins or filters, tailored specifically for the business use case.

2. Query Classes or Query Objects

   • Instead of bloating a repository with many query methods, group queries into separate classes responsible for particular query operations.
   • For example:

     public class InvoiceQueries
     {
         public static IQueryable<Invoice> OverdueInvoices(AppDbContext context)
         {
             return context.Invoices.Where(i => i.DueDate < DateTime.Today && !i.IsPaid);
         }
     }

   • Your repository or service calls these query objects to execute complex LINQ queries.

3. Extension Methods

   • Define reusable query extensions for IQueryable<T> representing complex filter logic:

     public static class InvoiceExtensions
     {
         public static IQueryable<Invoice> Overdue(this IQueryable<Invoice> query)
         {
             return query.Where(i => i.DueDate < DateTime.Today && !i.IsPaid);
         }
     }

   • Usage keeps repositories lean while enabling complex filters.

4. Raw SQL or Compiled Queries

   • For very complex or performance-critical queries, repositories may use raw SQL or EF Core compiled queries cached for repeated use.
   • Example:

     var overdueInvoices = await _context.Invoices
         .FromSqlRaw("SELECT * FROM Invoices WHERE DueDate < {0} AND IsPaid = 0", DateTime.Today)
         .ToListAsync();

Summary Table

Approach	Description	When to Use
Specific Repository	Custom methods with optimized query logic	Business-critical complex queries
Query Classes	Separate classes encapsulating queries	To organize queries and avoid bloating
Extension Methods	Reusable LINQ query filters	For common filtering or sorting
Raw SQL/Compiled	Use raw SQL or compile queries for performance	Very complex or performance-sensitive

This approach keeps your generic repository simple and delegates complex retrieval logic to specialized places, improving maintainability and testability.[5][7]

If desired, detailed code examples for any specific pattern can be provided.

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