c# - Is it possible to compile and execute new code at runtime in .NET?

Question

Note: Mathematical expression evaluation is not the focus of this question. I want to compile and execute new code at runtime in .NET. That being said...

I would like to allow the user to enter any equation, like the following, into a text box:

x = x / 2 * 0.07914
x = x^2 / 5

And have that equation applied to incoming data points. The incoming data points are represented by x and each data point is processed by the user-specified equation. I did this years ago, but I didn't like the solution because it required parsing the text of the equation for every calculation:

float ApplyEquation (string equation, float dataPoint)
{
    // parse the equation string and figure out how to do the math
    // lots of messy code here...
}

When you're processing boatloads of data points, this introduces quite a bit of overhead. I would like to be able to translate the equation into a function, on the fly, so that it only has to be parsed once. It would look something like this:

FunctionPointer foo = ConvertEquationToCode(equation);
....
x = foo(x);  // I could then apply the equation to my incoming data like this

Function ConvertEquationToCode would parse the equation and return a pointer to a function that applies the appropriate math.

The app would basically be writing new code at run time. Is this possible with .NET?

Answer 1

Yes! Using methods found in the Microsoft.CSharp, System.CodeDom.Compiler, and System.Reflection name spaces. Here is a simple console app that compiles a class ("SomeClass") with one method ("Add42") and then allows you to invoke that method. This is a bare-bones example that I formatted down to prevent scroll bars from appearing in the code display. It is just to demonstrate compiling and using new code at run time.

using Microsoft.CSharp;
using System;
using System.CodeDom.Compiler;
using System.Reflection;

namespace RuntimeCompilationTest {
    class Program
    {
        static void Main(string[] args) {
            string sourceCode = @"
                public class SomeClass {
                    public int Add42 (int parameter) {
                        return parameter += 42;
                    }
                }";
            var compParms = new CompilerParameters{
                GenerateExecutable = false, 
                GenerateInMemory = true
            };
            var csProvider = new CSharpCodeProvider();
            CompilerResults compilerResults = 
                csProvider.CompileAssemblyFromSource(compParms, sourceCode);
            object typeInstance = 
                compilerResults.CompiledAssembly.CreateInstance("SomeClass");
            MethodInfo mi = typeInstance.GetType().GetMethod("Add42");
            int methodOutput = 
                (int)mi.Invoke(typeInstance, new object[] { 1 }); 
            Console.WriteLine(methodOutput);
            Console.ReadLine();
        }
    }
}