CloudflareD1.NET.Linq 1.2.1

CloudflareD1.NET.Linq

LINQ query builder and object mapping extensions for CloudflareD1.NET. Provides type-safe query construction, automatic entity mapping, and fluent API for building SQL queries.

Installation

dotnet add package CloudflareD1.NET.Linq

Note: This package automatically includes CloudflareD1.NET as a dependency.

Features

• ✅ Fluent query builder - Chain methods like .Where(), .OrderBy(), .Take(), .Skip()
• ✅ Generic query methods - QueryAsync<T>(), QueryFirstOrDefaultAsync<T>(), etc.
• ✅ Automatic entity mapping - Maps query results to strongly-typed objects
• ✅ Snake_case to PascalCase conversion - Automatically maps database columns to C# properties
• ✅ Parameterized queries - Safe from SQL injection with ? placeholders
• ✅ Pagination support - Easy Take() and Skip() for paging
• ✅ Aggregate functions - CountAsync(), AnyAsync()
• ✅ Nullable type support - Handles nullable properties correctly
• ✅ Custom mappers - Implement IEntityMapper for custom mapping logic
• ✅ Performance optimized - Uses reflection caching for fast mapping

Quick Start

1. Define Your Entities

public class User
{
    public int Id { get; set; }
    public string Name { get; set; } = string.Empty;
    public string? Email { get; set; }
    public DateTime CreatedAt { get; set; }
    public bool IsActive { get; set; }
}

2. Use the Fluent Query Builder

using CloudflareD1.NET.Linq;

// Simple query with filtering
var activeUsers = await client.Query<User>("users")
    .Where("is_active = ?", true)
    .OrderBy("name")
    .ToListAsync();

// Pagination
var page2Users = await client.Query<User>("users")
    .OrderBy("created_at")
    .Skip(20)
    .Take(10)
    .ToListAsync();

// Complex filtering
var recentUsers = await client.Query<User>("users")
    .Where("created_at > ?", DateTime.UtcNow.AddDays(-7))
    .Where("is_active = ?", true)
    .OrderByDescending("created_at")
    .Take(50)
    .ToListAsync();

// Aggregates
var userCount = await client.Query<User>("users")
    .Where("email LIKE ?", "%@example.com")
    .CountAsync();

var hasUsers = await client.Query<User>("users")
    .Where("is_active = ?", true)
    .AnyAsync();

// Single result
var user = await client.Query<User>("users")
    .Where("id = ?", 123)
    .SingleOrDefaultAsync();

3. Direct SQL Queries with Type Mapping

// Query all users
var users = await client.QueryAsync<User>("SELECT * FROM users");

// Query with named parameters
var activeUsers = await client.QueryAsync<User>(
    "SELECT * FROM users WHERE is_active = @active",
    new { active = true }
);

// Get single user
var user = await client.QueryFirstOrDefaultAsync<User>(
    "SELECT * FROM users WHERE id = @id",
    new { id = 123 }
);

Query Builder API

Filtering

// Single WHERE clause with positional parameters
.Where("age > ?", 18)

// Multiple WHERE clauses (combined with AND)
.Where("age > ?", 18)
.Where("country = ?", "US")

// LIKE queries
.Where("email LIKE ?", "%@example.com")

// Complex conditions
.Where("(age > ? OR premium = ?) AND country = ?", 18, true, "US")

Sorting

// Single column ascending
.OrderBy("name")

// Single column descending
.OrderByDescending("created_at")

// Multiple columns
.OrderBy("country")
.ThenBy("city")
.ThenByDescending("created_at")

Pagination

// Skip first 20, take next 10
.Skip(20)
.Take(10)

// First page (10 per page)
.Take(10)

// Second page
.Skip(10)
.Take(10)

// Typical pagination pattern
int page = 2;
int pageSize = 10;
var results = await client.Query<User>("users")
    .OrderBy("id")
    .Skip((page - 1) * pageSize)
    .Take(pageSize)
    .ToListAsync();

Execution Methods

// Get all matching results
var list = await query.ToListAsync();

// Get first result or null
var first = await query.FirstOrDefaultAsync();

// Get exactly one result (throws if 0 or >1)
var single = await query.SingleAsync();

// Get exactly one result or null (throws if >1)
var singleOrNull = await query.SingleOrDefaultAsync();

// Get count of matching records
var count = await query.CountAsync();

// Check if any records match
var exists = await query.AnyAsync();

Select() Projection with Computed Properties (v1.2.1+)

Select specific columns and compute new values on-the-fly:

// DTO class for projection
public class UserSummary
{
    public int Id { get; set; }
    public string Name { get; set; }
    public bool IsAdult { get; set; }
    public int YearsUntil65 { get; set; }
}

// Boolean computed properties
var adults = await client.Query<User>("users")
    .Select(u => new UserSummary { 
        Id = u.Id, 
        Name = u.Name,
        IsAdult = u.Age >= 18,
        YearsUntil65 = 65 - u.Age
    })
    .ToListAsync();

// Math operations
var orderSummary = await client.Query<Order>("orders")
    .Select(o => new {
        o.Id,
        Total = o.Price * o.Quantity,
        Discount = o.Price * 0.1m,
        FinalPrice = (o.Price * o.Quantity) - (o.Price * 0.1m)
    })
    .ToListAsync();

// Comparisons and boolean logic
var userFlags = await client.Query<User>("users")
    .Select(u => new {
        u.Id,
        u.Name,
        u.Age,
        IsAdult = u.Age >= 18,
        IsMinor = u.Age < 18,
        IsSenior = u.Age >= 65,
        IsExpensive = u.MonthlyFee > 100
    })
    .ToListAsync();

// String methods
var formattedUsers = await client.Query<User>("users")
    .Select(u => new {
        u.Id,
        UpperName = u.Name.ToUpper(),
        LowerEmail = u.Email.ToLower()
    })
    .ToListAsync();

Supported Operations:

• Comparisons: >, <, >=, <=, ==, !=
• Math: +, -, *, /
• Boolean logic: && (AND), || (OR), ! (NOT)
• String methods: ToUpper(), ToLower(), Contains(), StartsWith(), EndsWith()

Advanced Usage

Custom Entity Mapper

Create a custom mapper for special mapping logic:

public class CustomUserMapper : IEntityMapper
{
    public T Map<T>(Dictionary<string, object?> row)
    {
        if (typeof(T) == typeof(User))
        {
            var user = new User
            {
                Id = Convert.ToInt32(row["user_id"]),
                Name = row["full_name"]?.ToString() ?? "",
                Email = row["email_address"]?.ToString()
            };
            return (T)(object)user;
        }
        throw new NotSupportedException($"Type {typeof(T)} not supported");
    }

    public IEnumerable<T> MapMany<T>(IEnumerable<Dictionary<string, object?>> rows)
    {
        return rows.Select(Map<T>);
    }
}

// Use custom mapper
var users = await client.QueryAsync<User>(
    "SELECT * FROM users",
    parameters: null,
    mapper: new CustomUserMapper()
);

// Or with query builder
var users = await client.Query<User>("users", new CustomUserMapper())
    .Where("is_active = ?", true)
    .ToListAsync();

Type Conversions

The default mapper automatically handles:

• Primitives: int, long, decimal, float, double, bool, byte, short
• Strings: Direct assignment
• DateTime: Parsed from strings or numeric timestamps
• Guid: Parsed from strings
• Enums: Parsed from strings or integers
• Nullable types: All of the above with ? suffix
• SQLite booleans: Converts 0/1 to false/true

public class Product
{
    public int Id { get; set; }
    public string Name { get; set; } = "";
    public decimal Price { get; set; }
    public DateTime? LastUpdated { get; set; }  // Nullable
    public ProductStatus Status { get; set; }   // Enum
    public bool IsActive { get; set; }          // SQLite stores as 0/1
}

public enum ProductStatus
{
    Draft,
    Published,
    Archived
}

Column Name Mapping

The default mapper automatically converts snake_case column names to PascalCase properties:

• user_id → UserId
• email_address → EmailAddress
• created_at → CreatedAt
• is_active → IsActive

// Database columns: user_id, full_name, email_address, created_at
public class User
{
    public int UserId { get; set; }        // Maps from user_id
    public string FullName { get; set; }   // Maps from full_name
    public string EmailAddress { get; set; } // Maps from email_address
    public DateTime CreatedAt { get; set; }  // Maps from created_at
}

Performance

• Reflection caching: Property info is cached using ConcurrentDictionary
• Mapping cache: Column-to-property mappings are cached per type
• Minimal overhead: <1ms for 1000 rows on typical hardware
• Lazy execution: Queries are only executed when you call an execution method

Performance Tips

1. Reuse mappers: Create one mapper instance and reuse it
2. Use Take() for limits: Reduces data transfer and processing
3. Project only needed columns: SELECT id, name instead of SELECT *
4. Use CountAsync() for counts: More efficient than .ToListAsync().Count()
5. Use AnyAsync() for existence checks: More efficient than checking count

Examples

Pagination with Total Count

var query = client.Query<Product>("products")
    .Where("category = ?", "Electronics");

var total = await query.CountAsync();
var page1 = await query.Skip(0).Take(20).ToListAsync();

Console.WriteLine($"Showing {page1.Count()} of {total} products");

Search with Multiple Filters

var searchTerm = "%laptop%";
var minPrice = 500m;
var maxPrice = 2000m;

var results = await client.Query<Product>("products")
    .Where("name LIKE ?", searchTerm)
    .Where("price >= ?", minPrice)
    .Where("price <= ?", maxPrice)
    .Where("is_active = ?", true)
    .OrderBy("price")
    .ToListAsync();

Complex Joins (using direct SQL)

var ordersWithCustomers = await client.QueryAsync<OrderWithCustomer>(@"
    SELECT 
        o.id as order_id,
        o.total as order_total,
        c.id as customer_id,
        c.name as customer_name
    FROM orders o
    INNER JOIN customers c ON o.customer_id = c.id
    WHERE o.created_at > @since
    ORDER BY o.created_at DESC
    ",
    new { since = DateTime.UtcNow.AddDays(-30) }
);

What's New

v1.2.1 - Computed Properties in Select()

• ✅ Computed properties - Use expressions in projections: .Select(u => new { u.Name, IsAdult = u.Age >= 18 })
• ✅ Math operations - Calculate values: Total = u.Price * u.Quantity, Discount = u.Price * 0.1m
• ✅ Boolean expressions - Create flags: IsExpensive = u.Price > 100, IsMinor = u.Age < 18
• ✅ String methods - Transform text: UpperName = u.Name.ToUpper()

v1.2.0 - Select() Projection

• ✅ Select() projection - Select specific columns: .Select(u => new { u.Id, u.Name })
• ✅ DTO mapping - Project to strongly-typed DTOs
• ✅ Performance optimization - Reduce data transfer by selecting only needed columns

v1.1.0 - Expression Tree LINQ

• ✅ Expression tree support - Type-safe queries: .Where(u => u.Age >= 18)
• ✅ Lambda expressions - Full IntelliSense and compile-time checking
• ✅ OrderBy expressions - .OrderBy(u => u.Name), .ThenBy(u => u.CreatedAt)

Coming Soon

• 🚧 Include() for joins - Automatic join and nested object mapping
• 🚧 GroupBy() support - Aggregate queries with grouping
• 🚧 IQueryable<T> - Full deferred execution support

Related Packages

• CloudflareD1.NET - Core D1 client (NuGet)
• CloudflareD1.NET.Migrations - Schema migrations (coming soon)
• CloudflareD1.NET.Testing - Testing helpers (coming soon)

License

MIT License - see LICENSE file for details

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Support

• 📦 NuGet Package
• 🐛 Issue Tracker
• 📖 Documentation