DjOrm

A lightweight ORM for .NET that maps C# classes to PostgreSQL tables using custom attributes and a generic DbContext<T>.

Features

• Auto-generates CREATE TABLE SQL from annotated C# entities
• Junction table generation for entity relationships
• Full CRUD operations via a single generic context
• Translates simple LINQ expressions into SQL WHERE clauses
• Recursive fetching of related objects via junction tables
• Async throughout

Usage

1. Annotate your entities

[TableAttribute]
public class CarEntity
{
    [PrimaryKeyAttribute]
    public int Id { get; set; }
    public string Name { get; set; }
    public string Make { get; set; }

    [SecondaryKeyAttribute]
    public DriverEntity? Driver { get; set; }
}

2. Create tables and run queries

var db = new DatabaseConnector(connString);

// Auto-create tables from entity definitions
var entities = new TableEntitiesMaker(new TypeTranslator()).CreateObjectEntities();
await db.ExecuteCommands(new SqlCreateTablesTranslator(entities).TranslateEntitiesToCreateTables());

// CRUD
IDbContext<CarEntity> ctx = new DbContext<CarEntity>(db);

await ctx.InsertData(new CarEntity("Civic", "Honda", driver));
var all    = await ctx.GetData();
var hondas = await ctx.GetDataBy(x => x.Make == "Honda" && x.Name != "Accord");
await ctx.UpdateData(car);
await ctx.DeleteData(car);

LINQ expression support — GetDataBy walks the expression tree and translates binary expressions (==, !=, <, <=, >, >=, &&, ||) directly into parameterized SQL conditions.

3. Recursive fetching of related objects

Pass recursive: true (or isRecursive: true on DbContext) to automatically load related entities via their junction tables:

// Fetch all articles and populate their related TagEntity objects
var articles = await ctx.GetData(isRecursive: true);

// Same with a filter
var articles = await ctx.GetDataBy(x => x.Title == "Hello", isRecursive: true);

For each fetched object, DjOrm:

1. Queries the junction table ({ParentType}{RelatedType}) using the parent's primary key.
2. Looks up the related entity by its primary key.
3. Assigns the result to the [SecondaryKey]-annotated property.

This works recursively — related objects that themselves have [SecondaryKey] properties are also populated.

Configuration

Connection string is loaded from a .env file:

HOST=localhost
PORT=5432
USERNAME=postgres
PASSWORD=postgres
DATABASE=testdb