// C# Eval Expression

// Doc: https://eval-expression.net/my-first-evaluation

​

// @nuget: Z.Expressions.Eval

​

/*

## Evaluate a C# expression with variables

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In the last example, we created the list dynamically in the `Execute` method and hardcoded the value `2`, which we used to filter. However, those values will be from existing variables and user input in most real-life scenarios.

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The `Execute` method takes variables to use in our expression as the second parameter (or all remaining parameters).

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There are multiple different ways of passing variables, such as:

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- Anonymous Type

- Class Member

- Dictionary

- Expando Object

- Values

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In this example, we will create the `list` and `greaterThan` variables and show different ways to pass those variables to our expression.

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See more: https://eval-expression.net/my-first-evaluation

*/

​

using System;

using System.Dynamic;

using System.Collections.Generic;

using Z.Expressions;

​

public class Program

{

    public static void Main()

    {

        var list = new List<int>() { 1, 2, 3, 4 };

        var greaterThan = 2;

​

        // Passing parameters with an Anonymous Type

        {

            var rList = Eval.Execute("list.Where(x => x > greaterThan)", new { list, greaterThan });

            FiddleHelper.WriteTable((IEnumerable<int>)rList);

        }       

​

        // Passing parameters with an Anonymous Type using named members

        {

            var rList = Eval.Execute("listName.Where(x => x > greaterThanName)", new { listName = list, greaterThanName = greaterThan });

            FiddleHelper.WriteTable((IEnumerable<int>)rList);

        }       

​

        // Passing parameters with a class instance and using class members

        // NOTE: When only using 1 parameter, you can directly use member names, "Item1" and "Item2" in the case of a Tuple<,>

        {

            var rList = Eval.Execute("Item1.Where(x => x > Item2)", new Tuple<List<int>, int>(list, greaterThan));

            FiddleHelper.WriteTable((IEnumerable<int>)rList);

        }       

​

        // Passing parameters with a Dictionary and using key names

        // NOTE: When only using 1 parameter, you can directly use dictionary key names in the expression

        {

            var dictionary = new Dictionary<string, object>();

            dictionary.Add("list", list);

            dictionary.Add("greaterThan", greaterThan);

            var rList = Eval.Execute("list.Where(x => x > greaterThan)", dictionary);

            FiddleHelper.WriteTable((IEnumerable<int>)rList);

        }

​

        // Passing parameters using an Expando Object and using member names

        // NOTE: When only using 1 parameter, you can directly use member names of the Expando Object

        {

            dynamic expandoObject = new ExpandoObject();

            expandoObject.list = list;

            expandoObject.greaterThan= greaterThan;

            var rList = Eval.Execute("list.Where(x => x > greaterThan)", expandoObject);

            FiddleHelper.WriteTable((IEnumerable<int>)rList);

        }

​

        // Passing parameters directly with the Values

        // NOTE: Because parameters are not named, you need to use the position as our library is not aware of the name "list" and "greaterThan"

        {

            var rList = Eval.Execute("{0}.Where(x => x > {1})", list, greaterThan);

​

            FiddleHelper.WriteTable((IEnumerable<int>)rList);

        }

    }

}