Bits of .NET

🔍 API Query = Filtering & Sorting

APIs need flexible queries. Filtering, sorting, and pagination make APIs powerful.

📝 Query Parameters

# Filtering
GET /api/users?status=active
GET /api/users?age=30
GET /api/users?age=gte:30
GET /api/users?name=John

# Sorting
GET /api/users?sort=name
GET /api/users?sort=-createdAt
GET /api/users?sort=name,-createdAt

# Pagination
GET /api/users?page=2&limit=20
GET /api/users?offset=20&limit=20
GET /api/users?cursor=123&limit=20

# Combining Queries
GET /api/users?status=active&sort=-createdAt&page=2

# Field Selection
GET /api/users?fields=id,name,email
GET /api/products?fields=id,name,price

# Text Search
GET /api/products?search=laptop
GET /api/products?q=wireless+headphones

🎯 Implementation

// Query Builder
public class QueryBuilder where T : class
{
    private IQueryable _query;

    public QueryBuilder(IQueryable query)
    {
        _query = query;
    }

    public QueryBuilder Filter(QueryFilter filter)
    {
        foreach (var condition in filter.Conditions)
        {
            _query = _query.Where(CreateExpression(condition));
        }
        return this;
    }

    public QueryBuilder Sort(QuerySort sort)
    {
        if (sort.IsDescending)
        {
            _query = _query.OrderByDescending(CreateOrderExpression(sort.Field));
        }
        else
        {
            _query = _query.OrderBy(CreateOrderExpression(sort.Field));
        }
        return this;
    }

    public QueryBuilder Page(int page, int limit)
    {
        _query = _query.Skip((page - 1) * limit).Take(limit);
        return this;
    }

    public QueryResult Build()
    {
        return new QueryResult
        {
            Data = _query.ToList(),
            Total = _query.Count()
        };
    }
}

// Usage
var result = new QueryBuilder(db.Users)
    .Filter(new { status = "active" })
    .Sort(new { field = "name", descending = false })
    .Page(2, 20)
    .Build();

💡 API Query Tips

• Use consistent naming
• Support common operators
• Validate query parameters
• Set sensible defaults
• Document query options