expression tree

An expression tree is an efficient data representation of a query  lambda expression. In terms of LINQ to SQL, the expression tree gets converted to SQL to ensure the filtering and ordering are performed on the server. For lambda expressions, IL code or an expression tree can be generated. If an operator accepts an expression for a method delegate, IL code is emitted.If an operator accepts an expression of a method delegate, the expression tree is returned. LINQ to SQL objects generate IL code because it takes in a generic delegate, whereas LINQ to SQL implementation takes an expression tree that gets converted to SQL to be executed by SQL Server.