## Why to use Hashids? [Hashids](https://github.com/ullmark/hashids.net) helps you to convert a number Id to a string, this can make your app a little more secure hiding the actual id or related key of your DB when the data is requested by an API. ## Why is useful ValueConverter of AutoMapper? [ValueConverter](https://docs.automapper.org/en/stable/Value-converters.html) can handle the convertion inside te `.Map(source)` method allowing you put the convertion logic in only one place. ## The model ```c# //Model of your data public class Student { public int Id { get; set; } public string Name { get; set; } public int ClassEnrollmentId { get; set; } } //Data Transfer Object (DTO) for your client public class StudentDto { public string Id { get; set; } public string Name { get; set; } public string ClassEnrollmentId { get; set; } } ``` ## The configuration After you install the nuget packages: - `Install-Package hashids.net` - `Install-Package AutoMapper.Extensions.Microsoft.DependencyInjection` Add the following code to the Program.cs to use hashids and AutoMapper with dependency injection, if you prefer to use a class Startup you have to put it on the ConfigureServices method. ```c# builder.Services.AddSingleton(_ => new Hashids("this is my salt")); // Optional, you can set the length of the string // new Hashids("this is my salt", [the number you want]) builder.Services.AddAutoMapper(typeof(AutoMapperProfile)); ``` ### AutoMapperProfile ```c# using AutoMapper; // To use the Profile class public class AutoMapperProfile: Profile { public AutoMapperProfile() { //This configuration convert the int property who saves Ids to hash string CreateMap() .ForMember(d => d.Id, opt => opt.ConvertUsing()) .ForMember(d => d.ClassEnrollmentId, opt => opt.ConvertUsing()); //This configuration makes the oposite from the above configuration CreateMap() .ForMember(d => d.Id, opt => opt.ConvertUsing()) .ForMember(d => d.ClassEnrollmentId, opt => opt.ConvertUsing()); } } ``` ### Convertion classes ```c# using AutoMapper; //To use IValueConverter interface using HashidsNet; //To use IHashids interface public class HashFormatter : IValueConverter { private readonly IHashids hashids; public HashFormatter(IHashids hashids) { this.hashids = hashids; } public string Convert(int source, ResolutionContext context) { return hashids.Encode(source); } } public class IntFromHash : IValueConverter { private readonly IHashids hashids; public IntFromHash(IHashids hashids) { this.hashids = hashids; } public int Convert(string source, ResolutionContext context) { return hashids.DecodeSingle(source); } } ``` ## How to use it In a controller only have to inject AutoMapper and call the `.Map` method like this. ```c# public class StudentstController : ControllerBase { private readonly IMapper mapper; public StudentstController(IMapper mapper) { this.mapper = mapper; } [HttpGet] public IActionResult Get() { //Summaries is the data as List return Ok(mapper.Map>(Summaries)); } } ``` ## Result *Data without hash* ```json [ { "id": 1, "name": "Juan", "classEnrollmentId": 2 }, { "id": 2, "name": "Pedro", "classEnrollmentId": 1 } ] ``` *Data with hash* ```json [ { "id": "NV", "name": "Juan", "classEnrollmentId": "6m" }, { "id": "6m", "name": "Pedro", "classEnrollmentId": "NV" } ] ``` Thank you so much for reading this, I hope this be helpful.

luisnogal

How to use Hashids with AutoMapper

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