Microsoft.CodeAnalysis.CSharp.Scripting.CSharpScript is a new C# script engine.

var code = "(1 + 2).ToString()";
var run = await CSharpScript.RunAsync(code, ScriptOptions.Default);
var result = (string)run.ReturnValue;
Console.WriteLine(result); //output 3

You can compile and run any statements, variables, methods, classes or any code segments.

Microsoft.CSharp.CSharpCodeProvider can be used to compile C# classes.

var code = @"
    public class Abc {
       public string Get() { return ""abc""; }
    }
";

var options = new CompilerParameters();
options.GenerateExecutable = false;
options.GenerateInMemory = false;

var provider = new CSharpCodeProvider();
var compile = provider.CompileAssemblyFromSource(options, code);

var type = compile.CompiledAssembly.GetType("Abc");
var abc = Activator.CreateInstance(type);

var method = type.GetMethod("Get");
var result = method.Invoke(abc, null);

Console.WriteLine(result); //output: abc