What is Expression Trees?

Expression Trees was first introduced in C# 3.0 (Visual Studio 2008), where they were mainly used by LINQ providers. Expression trees represent code in a tree-like format, where each node is an expression (for example, a method call or a binary operation such as x < y).
You can also convert expression trees into compiled code and run it. This transformation enables dynamic modification of executable code as well as the execution of LINQ queries in various databases and the creation of dynamic queries.