/*

 * Useful for creating a select in ASP.NET Core, Razor Pages

 * Examples.Identities for a real application could be static or dynamic e.g. get table row count

 *

 * From NorthWind database

 * DECLARE @SelectText AS NVARCHAR(50) = N'Select';

 * SELECT -1 AS CategoryID, @SelectText AS CategoryName

 * UNION ALL

 * SELECT CategoryID, CategoryName

 * FROM dbo.Categories

 * ORDER BY CategoryName;

 */

​

using System;

using System.Collections.Generic;

using System.Linq;      

​

public class Program

{

    public static void Main()

    {

        Examples.ReorderDemo();

    }

}

​

public class Categories

{

    public int CategoryId { get; set; }

    public string CategoryName { get; set; }

​

    public override string ToString() => CategoryName;

}

​

internal class Examples

{

    public static void ReorderDemo()

    {

        var list = Categories;

        list = list.OrderBy(c => Identities.IndexOf(c.CategoryId)).ToList();

        list.ForEach(cat => Console.WriteLine(cat.ToString()));

    }

    public static List<int> Identities => Enumerable.Range(-1, 12).ToList();

    // mock-up for data read from NorthWind.Categories with SQL above

    public static List<Categories> Categories = new()

        {

            new() {CategoryId = 1, CategoryName = "Beverages"},

            new() {CategoryId = 2, CategoryName = "Condiments"},

            new() {CategoryId = 3, CategoryName = "Confections"},

            new() {CategoryId = 4, CategoryName = "Dairy Products"},

            new() {CategoryId = 5, CategoryName = "Grains/Cereals"},

            new() {CategoryId = 6, CategoryName = "Meat/Poultry"},

            new() {CategoryId = 7, CategoryName = "Produce"},

            new() {CategoryId = 8, CategoryName = "Seafood"},

            new() {CategoryId = -1, CategoryName = "Select"},

            new() {CategoryId = 9, CategoryName = "Wine"},

        };

}