SystemLinqExpressions

SystemLinqExpressions is a library designed to support construction, interrogation, and execution of expression trees at runtime. It provides a framework for representing code as data, enabling dynamic query construction, transformation, and evaluation within managed applications. It is often used to implement custom query providers, dynamic scripting, or runtime DSLs.

The library exposes a hierarchy of expression types, such as constants, parameters, binary operations, method calls, member access, conditional logic, lambdas, and blocks. Expressions are immutable data structures that describe a function or computation. A LambdaExpression pairs a body expression with a set of parameters to form a delegate or expression tree that can be compiled.

Users construct expression trees programmatically, inspect tree structure via visitors, and transform or rewrite trees using expression visitors. Trees can be compiled into delegates using a Compile method, producing fast, executable code. They serve as the input to LINQ providers that translate expression trees into another query language or runtime representation.

Although modeled after the System.Linq.Expressions namespace of the .NET platform, SystemLinqExpressions is a standalone or alternate implementation used across languages and runtimes that support expression trees. It is primarily used in data access layers, dynamic query generation, and meta-programming tasks.

The concept originated with the LINQ framework, with expression trees formalized in the later .NET releases. SystemLinqExpressions adheres to similar design principles, emphasizing type safety, debuggability, and cache-friendly compilation.