System.Linq.Expressions

Introduction

The System.Linq.Expressions namespace provides classes that allow you to create and manipulate expression trees. Expression trees represent queries in a structured format, allowing you to work with them programmatically. This is useful for building custom LINQ query providers and for optimizing LINQ queries.

Creating Expressions

You can create expression trees using the Expression class and its derived classes. The Expression class represents a node in the expression tree. Different node types are available for representing different types of operations, such as arithmetic operations, logical operations, and property access.

Expression Tree Nodes

Expression tree nodes represent different types of operations. Some common nodes include:

• Constant: Represents a literal value (e.g., a number or string).
• Parameter: Represents a parameter in a LINQ query.
• BinaryOperatorExpression: Represents a binary operator (e.g., +, -, *, /).
• LambdaExpression: Represents a lambda expression.

Using Expressions with LINQ

You can use expression trees with LINQ queries using the QueryPart class. This allows you to create custom query providers that can optimize LINQ queries.

Example Code

                        
            Expression> add = x => x + 1;
            int result = add.Compile().Invoke(5);
            Console.WriteLine(result); // Output: 6