// C# Eval Expression

// Doc: https://eval-expression.net/linq-dynamic

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// @nuget: Z.Expressions.Eval

​

/*

## LINQ FirstOrDefaultDynamic Method

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The LINQ FirstOrDefaultDynamic returns the first element of a sequence, or a default value if no element is found. You can use a dynamic string expression to filter elements that satisfy the condition.

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In this example, we will create a list of product and return the first product or null by dynamically filtering them with their type.

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See more: https://eval-expression.net/linq-dynamic

*/

​

using System;

using System.Collections.Generic;

using System.Linq;

using Z.Expressions;

​

public class Program

{

    public static void Main()

    {

        var product1 = new Product() { Name = "C# Eval Expression", Url = "https://eval-expression.net/", Type = "Paid" };

        var product2 = new Product() { Name = "Dapper Plus", Url = "https://dapper-plus.net/", Type = "Paid" };

        var product3 = new Product() { Name = "Entity Framework Extensions", Url = "https://entityframework-extensions.net/", Type = "Paid" };

        var product4 = new Product() { Name = ".NET Fiddle", Url = "https://dotnetfiddle.net/", Type = "Free" };

        var product5 = new Product() { Name = "SQL Fiddle", Url = "https://sqlfiddle.com/", Type = "Free" };

        var product6 = new Product() { Name = "ZZZ Code AI", Url = "https://zzzcode.ai/", Type = "Free" };

        var list = new List<Product>() { product1, product2, product3, product4, product5, product6 };

        var firstOrDefault1 = list.FirstOrDefaultDynamic("x => x.Type == 'Paid'");

        var firstOrDefault2 = list.FirstOrDefaultDynamic("x => x.Type == type", new { type = "Paid" });

        FiddleHelper.Dump(firstOrDefault1);

        FiddleHelper.Dump(firstOrDefault2);

    }

    public class Product

    {

        public string Name { get; set; }

        public string Url { get; set; }

        public string Type { get; set; }

    }

}

​

​