Custom Providers

ExpressiveSharp is not tied to EF Core or MongoDB — it works with any IQueryable<T>. This page covers how to use it with your own provider, a third-party LINQ provider, or even LINQ to Objects.

The Core Contract

The ExpressiveSharp package provides two provider-neutral entry points:

• .AsExpressive() — wraps any IQueryable<T> in an IExpressiveQueryable<T>. Modern C# syntax works in the query; [Expressive] members are expanded; the normalized expression tree is handed to the underlying provider.
• ExpressionPolyfill.Create(...) — builds an Expression<TDelegate> from a delegate lambda that uses modern syntax, for cases where you need a bare expression tree rather than a queryable.

Neither of these requires EF Core, MongoDB, or any specific provider assembly.

Wrapping an IQueryable

Any IQueryable<T> works:

using ExpressiveSharp;

IQueryable<Customer> raw = GetCustomers();       // your own provider
var customers = raw.AsExpressive();

var results = customers
    .Where(c => c.Email != null && c.IsVip)      // [Expressive] + modern syntax
    .Select(c => new { c.Name, c.Email })
    .ToList();

The query runs through your provider's own translation pipeline after ExpressiveSharp has:

1. Expanded [Expressive] member accesses into their generated expression trees
2. Normalized the tree via the built-in transformers (null-conditional flattening, block lifting, tuple comparison flattening)

LINQ to Objects

The same extension works on IEnumerable<T>.AsQueryable():

var people = peopleList.AsQueryable().AsExpressive();

var filtered = people
    .Where(p => p.Employer?.Name == "Acme" && p.IsActive)  // [Expressive] IsActive
    .ToList();

Useful for unit tests or in-memory scenarios where you want the same [Expressive] logic you use in your database code path.

ExpressionPolyfill.Create

Sometimes you don't have a queryable — you need an Expression<Func<T, bool>> to pass to a method that takes one. ExpressionPolyfill.Create builds that expression from a delegate lambda, so you can use modern syntax inline:

using ExpressiveSharp;

Expression<Func<Customer, bool>> predicate =
    ExpressionPolyfill.Create((Customer c) => c.Email?.Length > 5);

// Use it with your own API that takes Expression<T>
provider.Query(predicate);

See ExpressionPolyfill.Create for the full API.

Implementing a Custom Plugin

If you're building a provider and want to ship ExpressiveSharp-specific transformers (e.g., to handle a dialect quirk), implement IExpressionTreeTransformer and register it via the plugin architecture. See Custom Transformers for the full walkthrough.

Next Steps

• IExpressiveQueryable<T> — full API surface
• ExpressionPolyfill.Create — build Expression<T> inline
• Custom Transformers — hook into the pipeline