Explain the concept of expression trees and their role in computer science.

An expression tree is a tree data structure where each node represents an operation or an operand (constant, variable). In computer science, it is used to represent and analyze expressions, such as arithmetic or logical expressions.

Role of an expression tree:

• Allows easy parsing and evaluation of complex expressions.
• Used in compilers for syntax analysis and code optimization.
• In C#, expression trees are used to build dynamic queries, for example in LINQ, where expressions can be analyzed and transformed at runtime.

Example of a simple expression tree for the expression (2 + 3) * 4:

      *
     / \
    +   4
   / \
  2   3

Each node is an operation (*, +), leaves are operands (2, 3, 4).