C# 0 The Complete Reference

System.Linq.Expressions.Expression

 class. Expression trees are useful in situations in 

which a query will be executed by something outside the program, such as a database that 

uses SQL. By representing the query as data, the query can be converted into a format 

understood by the database. This process is used by the LINQ to SQL feature provided by 

Visual C#, for example. Thus, expression trees help C# support a variety of data sources.

You can obtain an executable form of an expression tree by calling the