LiteDB - A .NET NoSQL Document Store in a single data file

// Create your POCO class
public class Customer
{
    public int Id { get; set; }
    public string Name { get; set; }
    public int Age { get; set; }
    public string[] Phones { get; set; }
    public bool IsActive { get; set; }
}

// Open database (or create if doesn't exist)
using(var db = new LiteDatabase(@"MyData.db"))
{
    // Get customer collection
    var col = db.GetCollection<Customer>("customers");

    // Create your new customer instance
    var customer = new Customer
    { 
        Name = "John Doe", 
        Phones = new string[] { "8000-0000", "9000-0000" }, 
        Age = 39,
        IsActive = true
    };

    // Create unique index in Name field
    col.EnsureIndex(x => x.Name, true);

    // Insert new customer document (Id will be auto-incremented)
    col.Insert(customer);

    // Update a document inside a collection
    customer.Name = "Joana Doe";

    col.Update(customer);

    // Use LINQ to query documents (with no index)
    var results = col.Find(x => x.Age > 20);
}

// DbRef to cross references
public class Order
{
    public ObjectId Id { get; set; }
    public DateTime OrderDate { get; set; }
    public Address ShippingAddress { get; set; }
    public Customer Customer { get; set; }
    public List<Product> Products { get; set; }
}        

// Re-use mapper from global instance
var mapper = BsonMapper.Global;

// "Products" and "Customer" are from other collections (not embedded document)
mapper.Entity<Order>()
    .DbRef(x => x.Customer, "customers")   // 1 to 1/0 reference
    .DbRef(x => x.Products, "products")    // 1 to Many reference
    .Field(x => x.ShippingAddress, "addr"); // Embedded sub document
            
using(var db = new LiteDatabase("MyOrderDatafile.db"))
{
    var orders = db.GetCollection<Order>("orders");
        
    // When query Order, includes references
    var query = orders
        .Include(x => x.Customer)
        .Include(x => x.Products) // 1 to many reference
        .Find(x => x.OrderDate <= DateTime.Now);

    // Each instance of Order will load Customer/Products references
    foreach(var order in query)
    {
        var name = order.Customer.Name;
        ...
    }
}