// C# Eval Expression

// Doc: https://eval-expression.net/options

​

// @nuget: Z.Expressions.Eval

​

/*

## CacheKeyPrefix

​

The CacheKeyPrefix option lets you get or set the prefix in the Cache Key. That option can be helpful if you want to make the cache key more unique. By default, the CacheKeyPrefix value is `[evalContext].GetType().FullName` (The full name of the EvalContext type). 

​

In this example, we will register a static method and call our context `Execute` method. Then we will unregister this static method and use the expression again, and we will see the `Execute` is still working. That is still working because the library does not compile the expression but instead takes the delegate previously created directly from the cache. So to reset the cache, we will set another `CacheKeyPrefix` and try again to execute our expression, which will correctly fail this time.

​

See more: https://eval-expression.net/options

*/

​

using System;

using System.Collections.Generic;

using System.Reflection;

using Z.Expressions;

​

public class Program

{

    public static void Main()

    {

        // Global Context: EvalManager.DefaultContext.CacheKeyPrefix = "Another Cache Key";

        var context = new EvalContext();

        context.RegisterStaticMethod(typeof(Program));

        var r1 = context.Execute<int>("AddMe(1, 2)");

        Console.WriteLine("1 - Result:" + r1);

        context.UnregisterStaticMethod(typeof(Program));

        // Oops! Even if unregistering the `AddMe` method, the expression still succeeds as we take the delegate from the cache

        var r2 = context.Execute<int>("AddMe(1, 2)");

        Console.WriteLine("2 - Result:" + r2);

        try

        {

            // By changing the cache key, we somewhat reset the cache so the expression will not compile anymore

            context.CacheKeyPrefix = "Another Cache Key";

            var fail = context.Execute<int>("AddMe(1, 2)");

        }

        catch(Exception ex)

        {

            Console.WriteLine("3 - Exception: " + ex.Message);

        }

    }

    public static int AddMe(int x, int y)

    {

        return x + y;

    }

}

​

​