Automapper：将 int 转换为字符串

Question

我目前在我的 c# MVC 项目中使用 AutoMapper，并且遇到了从整数转换为字符串的问题。

我有两个班级：

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; }
{

使用 Automapper 我想将 Job 类中的所有三个属性连接起来形成一个字符串，然后将其映射到 JobViewModel 类中的 JobNumberFull。：

前缀-JobNumber-Year

首先我保持简单，没有将字段连接成一个字符串，我只是尝试获取 JobNumber (int) 并将其映射到 JobNumberFull (string)，如下所示：

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();

当我运行它时，我得到以下错误

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

我知道这是为了

Convert.ToString

但我不知道该怎么办！从字符串转换为 int 时，我可以执行 Convert.ToInt32 ，它就像一种享受。我需要创建自定义类型转换器吗？

我将如何获取字符串 prefix-jobnumber-year？

非常感谢所有帮助。

---

更新

感谢 Jeremy 和 AutoMapper 网站的帮助，我设法让这个工作在这里是我的解决方案，如果您认为有更优雅的解决方案，请随时发表评论：

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

我觉得你可以用ResolveUsing的方法来解决。

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

您需要为从 Job 到 JobViewModel 的转换指定自定义转换函数。

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

要将 Job 转换为 JobViewModel，请使用 Map 函数。

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

要将作业列表转换为 JobViewModel，请使用 Select 扩展方法。

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