C# - Convert a string (which contains method or function) to an actual function or method in C#

Question

I have a string. For example

 string str="if(a>b) {return a;} else {return b;}"

I want to evaluate or make function, say func(int a, int b) which will have the code of 'str'.

Answer 1

you may need to use CSharpCodeProvider as in this answer

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.CSharp;
using System.CodeDom.Compiler;

class Program
{
    static void Main(string[] args)
    {
        var csc = new CSharpCodeProvider(new Dictionary<string, string>() { { "CompilerVersion", "v3.5" } });
        var parameters = new CompilerParameters(new[] { "mscorlib.dll", "System.Core.dll" }, "foo.exe", true);
        parameters.GenerateExecutable = true;
        CompilerResults results = csc.CompileAssemblyFromSource(parameters,
        @"using System.Linq;
            class Program {
              public static void Main(string[] args) {
                var q = from i in Enumerable.Range(1,100)
                          where i % 2 == 0
                          select i;
              }
            }");
        results.Errors.Cast<CompilerError>().ToList().ForEach(error => Console.WriteLine(error.ErrorText));
    }
}

Answer 2

In general, this is not an easy thing to do, but the System.CodeDom namespace is where your journey will start.

Look at the following CodeProject article on the matter as a start: http://www.codeproject.com/Articles/26312/Dynamic-Code-Integration-with-CodeDom

The basics of it is as follows (as taken from the codeproject article):

private static Assembly CompileSource( string sourceCode )
{
   CodeDomProvider cpd = new CSharpCodeProvider();
   CompilerParameters cp = new CompilerParameters();
   cp.ReferencedAssemblies.Add("System.dll");
   //cp.ReferencedAssemblies.Add("ClassLibrary1.dll");
   cp.GenerateExecutable = false;
   // Invoke compilation.
   CompilerResults cr = cpd.CompileAssemblyFromSource(cp, sourceCode);

   return cr.CompiledAssembly;
}

The resultant assembly will have the class/method/code you are interested in, and then you can use reflection to call your method. Since your example just uses a code fragment, you will probably have to wrap it in a class/method before passing it to this method.

I hope that helps, but dynamic code generation in C# is not easy and this is just a start.