Question

Consider this code fragment;

int sum = 0;
sum = Expression.Evaluate("1+1");

where the value of sum = 2

I do have an expression that will compute values but i want that expression to be build programatically then evaluate the result. I don’t have any idea what class or namespace that I will dealing with. Anyone can help me.

Answer 1

You could use Expression Trees:

Expression trees represent code in a tree-like data structure, where
each node is an expression, for example, a method call or a binary
operation such as x < y.

You can compile and run code represented by expression trees.

• Expression Trees (C# and Visual Basic)

• Expression Tree Basics

Note: This problem can be solved using System.Reflection.Emit and work directly with MSIL, but the resulting code is hard to write and read.

After a little browsing, I suggest you checkout Flee on Codeplex: Fast Lightweight Expression Evaluator :

Flee is an expression parser and evaluator for the .NET framework. It
allows you to compute the value of string expressions such as sqrt(a^2
+ b^2) at runtime. It uses a custom compiler, strongly-typed expression language, and lightweight codegen to compile expressions
directly to IL. This means that expression evaluation is extremely
fast and efficient.