c# how to passing functions as string to methods

Question

Is it possible to pass a function (like let's say sin() ) via string and then use it as int?

Like: (main idea only)

public int getfunc(String func)
{
   return res_of(func)
}

I tried playing around with string of "Math.sin(0)" but couldn't print the 0...

I could predefine the math functions since I only need 1 and then it becomes extremely simple as I only pass the int value for the function to work on, but I thought may-hap there is a way to keep it more generic.

I do not want to use mapping of the functions I want to keep it dynamic.... is ther a way of doing so?

You mean, you want to pass a string and execute that string in the code ? — André Silva
– André Silva, Commented Nov 21, 2013 at 10:33
Maybe you should provide an example of how you intend on using this. Maybe there is a better way, or at least is will help us understand your needs a bit more — musefan
– musefan, Commented Nov 21, 2013 at 10:35
You most probably want to use delegates. It's unlikely that you really need to compile a string expression in runtime. — vgru
– vgru, Commented Nov 21, 2013 at 10:37

Matthew Watson · Accepted Answer · 2013-11-21 10:39:32Z

I'd like to offer an alternative approach that you may not have considered.

You could use a delegate instead of passing a string; that way, you won't need any reflection.

There's a predefined delegate type in C# called Func<> which lets you easily define the return type and parameter types of a method that you want to pass as a delegate.

For example, the Func<> for Math.Sin(double) would be Func<double, double> because Math.Sin() returns a double and takes a double parameter.

An example will make this clearer:

using System;

namespace Demo
{
    internal class Program
    {
        private void run()
        {
            Func<double, double> f1 = Math.Sin;
            Func<double, double> f2 = Math.Cos;

            double r1 = runFunc(f1, 1.0);
            double r2 = runFunc(f2, 2.0);

            Console.WriteLine(r1);
            Console.WriteLine(r2);
        }

        private static double runFunc(Func<double, double> func, double parameter)
        {
            return func(parameter);
        }

        private static void Main()
        {
            new Program().run();
        }
    }
}

Jakub Konecki · Accepted Answer · 2013-11-21 10:35:33Z

2

Try using http://www.csscript.net/

 dynamic script = CSScript.Evaluator
                         .LoadCode(@"using System;
                                     public class Script
                                     {
                                         public int Sum(int a, int b)
                                         {
                                             return a+b;
                                         }
                                     }");
int result = script.Sum(1, 2);

answered Nov 21, 2013 at 10:35

Jakub Konecki

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1 Comment

user2893825 Over a year ago

Unfortunately we are not allowed to use scripts since we did not learn scripts :( Regardless I coudln't get it to work. I will play around with it , as for it's a new way of thinking though I did not learn any of these tools.

Marton · Accepted Answer · 2013-11-21 10:40:05Z

1

Declare the method like this:

public int DoCalculation(Func<double, double> func, double a)
    {
        return Convert.ToInt32(func(a));
    }

Then use it like this:

int result = DoCalculation(Math.Sin, 3.3);

answered Nov 21, 2013 at 10:40

Marton

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Comments

Community · Accepted Answer · 2017-05-23 12:19:13Z

0

In our application we use the .NET integrated C# compiler.
This is some work to do but straight-forward to implement.

Here's an answer with a lot more details on that.
We use this in our companies production.

edited May 23, 2017 at 12:19

CommunityBot

11 silver badge

answered Nov 21, 2013 at 10:46

joe

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