# ExpressionHelpers

LINQ expression tree serialization and deserialization to JSON, enabling expression transport over SignalR or HTTP. Converts `Expression` trees to a recursive `AcExpressionNode` DTO and back, supporting binary, unary, lambda, member access, method calls, conditionals, new/member-init, and array expressions.

## Key Files

- **`AcExpressionNode.cs`** -- Universal DTO representing any expression node. Includes `ParameterNode` and `MemberBindingNode` supporting types. Recursively models the full expression tree and is JSON-serializable.
- **`AcExpressionHelper.cs`** -- Static facade for serializing/deserializing expressions and `IQueryable` query trees. Provides `ExpressionToJson`, `ExpressionFromJson`, `QueryToJson`, and `ApplyQueryFromJson` methods.
- **`AcExpressionSerializerVisitor.cs`** -- `ExpressionVisitor` subclass that walks an expression tree and builds the `AcExpressionNode` graph using a stack-based approach. Handles closure variable evaluation and constant serialization.
- **`AcExpressionDeserializer.cs`** -- Reconstructs `Expression` trees from `AcExpressionNode` DTOs. Resolves types, parameters, methods, and member bindings. Handles nullable type mismatches in binary expressions.