RealWorldExample.cs

// Parameter objects
public record ProductFilters(
    [FromQuery] string? Query,
    [FromQuery] string? Category,
    [FromQuery] decimal? MinPrice,
    [FromQuery] decimal? MaxPrice
);

public record PaginationParams(
    [FromQuery] int Page = 1,
    [FromQuery] int PageSize = 20
);

// You can even nest them if you want further separation
public record ProductSearchRequest(
    [AsParameters] ProductFilters Filters, // ⚠️ nesting [AsParameters] is not supported
    [AsParameters] PaginationParams Pagination
);

// Better: keep them flat at the handler level
app.MapGet("/products", async (
    [AsParameters] ProductFilters filters,
    [AsParameters] PaginationParams pagination,
    ProductsDb db,
    CancellationToken ct) =>
{
    var query = db.Products.AsQueryable();

    if (!string.IsNullOrEmpty(filters.Query))
        query = query.Where(p => p.Name.Contains(filters.Query));

    if (filters.Category is not null)
        query = query.Where(p => p.Category == filters.Category);

    if (filters.MinPrice is not null)
        query = query.Where(p => p.Price >= filters.MinPrice);

    if (filters.MaxPrice is not null)
        query = query.Where(p => p.Price <= filters.MaxPrice);

    var total = await query.CountAsync(ct);
    var items = await query
        .Skip((pagination.Page - 1) * pagination.PageSize)
        .Take(pagination.PageSize)
        .ToListAsync(ct);

    return Results.Ok(new { total, items });
});