Automapper: convert int to string

Question

I am currently using AutoMapper in my MVC C # project and have encountered the problem of converting from an integer to a string.

I have two classes:

public class Job { public string Prefix { get; set; } public int JobNumber { get; set; } public int Year { get; set } public int JobPriority { get; set; } public virtual EntityPriority EntityPriority { get; set; } } public class JobViewModel { public string JobNumberFull { get; set; } { 

Using Automapper, I would like to combine all three properties in the Job class to form a string that will then be mapped to JobNumberFull in the JobViewModel class .:

Prefix-Job_Number-year

To start, I saved everything simply and did not concatenate the fields into a string, I just tried to take JobNumber (int) and map it to JobNumberFull (string) as follows:

 Mapper.CreateMap<int, string>().ConvertUsing(Convert.ToString); Mapper.CreateMap<Job, JobViewModel>() .ForMember(d => d.JobPriorityId, opt => opt.MapFrom(s => s.EntityPriority.EntityPriorityID)) .ForMember(d => d.JobPriorityLevel, opt => opt.MapFrom(s => s.EntityPriority.PriorityLevel)) .ForMember(d => d.JobNumberFull, opt => opt.MapFrom(s => s.JobNumberYear)); Mapper.AssertConfigurationIsValid(); var jobsList = db.Jobs.Where(j => j.OperationID == operationId).Project().To<JobViewModel>().ToList(); 

When I run this, I get the following error:

 Type 'System.String' does not have a default constructor 

I know this is due to

 Convert.ToString 

but I'm not sure what to do with it! I can do Convert.ToInt32 when switching from string to int, and it works as a pleasure. Do I need to create a custom type converter?

How can I get the string prefix-jobnumber-year?

All help is much appreciated.

---

UPDATE

Thanks to the help of Jeremy and the AutoMapper website, I managed to get this work, here is my solution, please feel free to comment if you think there is a more elegant solution:

 public class Job { public string Prefix { get; set; } public int JobNumber { get; set; } public int Year { get; set; } public int JobPriority { get; set; } public virtual EntityPriority EntityPriority { get; set; } } public class JobViewModel { public int JobNumber { get; set; } public int Year { get; set; } public string JobNumberFull { get; set; } } public enum EntityPriority { Normal = 0, High } public interface IValueResolver { ResolutionResult Resolve(ResolutionResult source); } public class JobNumberConverter : ValueResolver<Job, string> { protected override string ResolveCore(Job source) { return string.Format("{0}-{1}-{2}", source.Prefix, source.JobNumber, source.Year); } } public ActionResult Index() { Mapper.CreateMap<Job, JobViewModel>() .ForMember(jvm => jvm.JobNumberFull, opt => opt.ResolveUsing<JobNumberConverter>()); Mapper.AssertConfigurationIsValid(); List<Job> jobs = new List<Job>(); Job j = new Job() { JobNumber = 1, Prefix = "prefix", Year = 2013, EntityPriority = EntityPriority.High, JobPriority = 2 }; Job j2 = new Job() { JobNumber = 2, Prefix = "prefix", Year = 2013, EntityPriority = EntityPriority.High, JobPriority = 2 }; Job j3 = new Job() { JobNumber = 3, Prefix = "prefix", Year = 2013, EntityPriority = EntityPriority.High, JobPriority = 2 }; jobs.Add(j); jobs.Add(j2); jobs.Add(j3); var jobViewModels = jobs.Select(job => Mapper.Map<JobViewModel>(job)); return View(); } 

Answer 1

I think you can use the ResolveUsing method to solve it.

 Mapper.CreateMap<Job, JobViewModel>() .ForMember(d => d.JobNumberFull, exp => exp.ResolveUsing(j => string.Format("{0}-{1}-{2}", j.Prefix, j.JobNumber, j.Year))); 

Answer 2

You need to specify a custom conversion function to convert from Job to JobViewModel.

 Mapper.CreateMap<Job, JobViewModel>().ConvertUsing( job => new JobViewModel { JobNumberFull = string.Format("{0}-{1}-{2}", job.Prefix, job.JobNumber, Job.Year) }); 

To convert a job to JobViewModel, use the Map function.

 var jobViewModel = Mapper.Map<JobViewModel>(job); 

To convert the job list to JobViewModels, use Select Extension Method.

 var jobViewModels = jobs.Select(job => Mapper.Map<JobViewModel>(job));