Calling a function from a string in C#

I know in php you are able to make a call like:

$function_name = 'hello';
$function_name();

function hello() { echo 'hello'; }

Is this possible in .Net?

Yes. You can use reflection. Something like this:

Type thisType = this.GetType();
MethodInfo theMethod = thisType.GetMethod(TheCommandString);
theMethod.Invoke(this, userParameters);

With the above code, the method which is invoked must have access modifier public. If calling a non-public method, one needs to use the BindingFlags parameter, e.g. BindingFlags.NonPublic | BindingFlags.Instance:

Type thisType = this.GetType();
MethodInfo theMethod = thisType
    .GetMethod(TheCommandString, BindingFlags.NonPublic | BindingFlags.Instance);
theMethod.Invoke(this, userParameters);

You can invoke methods of a class instance using reflection, doing a dynamic method invocation:

Suppose that you have a method called hello in a the actual instance (this):

string methodName = "hello";

//Get the method information using the method info class
 MethodInfo mi = this.GetType().GetMethod(methodName);

//Invoke the method
// (null- no parameter for the method call
// or you can pass the array of parameters...)
mi.Invoke(this, null);

class Program
    {
        static void Main(string[] args)
        {
            Type type = typeof(MyReflectionClass);
            MethodInfo method = type.GetMethod("MyMethod");
            MyReflectionClass c = new MyReflectionClass();
            string result = (string)method.Invoke(c, null);
            Console.WriteLine(result);

        }
    }

    public class MyReflectionClass
    {
        public string MyMethod()
        {
            return DateTime.Now.ToString();
        }
    }

This code works in my console .Net application

class Program
{
	static void Main(string[] args)
	{
		string method = args[0]; // get name method
		CallMethod(method);
	}
	
	public static void CallMethod(string method)
	{
		try
		{
			Type type = typeof(Program);
			MethodInfo methodInfo = type.GetMethod(method);
			methodInfo.Invoke(method, null);
		}
		catch(Exception ex)
		{
			Console.WriteLine("Error: " + ex.Message);
			Console.ReadKey();
		}
	}
	
	public static void Hello()
	{
		string a = "hello world!";
		Console.WriteLine(a);
		Console.ReadKey();
	}
}

A slight tangent -- if you want to parse and evaluate an entire expression string which contains (nested!) functions, consider NCalc (http://ncalc.codeplex.com/ and nuget)

Ex. slightly modified from the project documentation:

// the expression to evaluate, e.g. from user input (like a calculator program, hint hint college students)
var exprStr = "10 + MyFunction(3, 6)";
Expression e = new Expression(exprString);

// tell it how to handle your custom function
e.EvaluateFunction += delegate(string name, FunctionArgs args) {
		if (name == "MyFunction")
			args.Result = (int)args.Parameters[0].Evaluate() + (int)args.Parameters[1].Evaluate();
	};

// confirm it worked
Debug.Assert(19 == e.Evaluate());

And within the EvaluateFunction delegate you would call your existing function.