. net设计模式MVVM与ViewModelService

在研究MVVM模式时，我经常在这个模式中遇到一个"services"组件，特别是在新的。net核心文档，webcast &;学习材料。

样本:

• 索引。cshtml(视图)
• HomeController(控制器)
• ViewModelService (?)
• IndexViewModel (ViewModel)
• IndexModel(模型)

使用额外的抽象层(ViewModelService)是MVVM模式的扩展和良好实践，还是该模式有另一个名称?对我来说，代码看起来很好也很干净，但是大多数MVVM模式的解释都没有使用ViewModelService来创建ViewModel并将其传递给控制器。

根据下面的代码，有一个ViewModelService层，而不是将ViewModel直接传递给控制器。

谢谢。

---

更新代码

Index.cshtml

@model FishTank.ViewModels.DashboardViewModel

HomeController.cs

public class HomeController: Controller
{
    private readonly IViewModelService viewModelService;
    public HomeController(IViewModelService viewModelService)
    { 
        this.viewModelService = viewModelService;
    }
    public IActionResult Index()
    {
        ViewBag.Title = "Fish tank dashboard";
        return View(viewModelService.GetDashboardViewModel());
    }
}

ViewModelService.cs

    public class ViewModelService : IViewModelService
{
    private readonly ISensorDataService sensorDataService;
    private readonly IUrlHelper urlHelper;
    public ViewModelService(ISensorDataService sensorDataService, IUrlHelperFactory urlHelperFactory, IActionContextAccessor actionContextAccessor)
    {
        this.sensorDataService = sensorDataService;
        urlHelper = urlHelperFactory.GetUrlHelper(actionContextAccessor.ActionContext);
    }
    public DashboardViewModel GetDashboardViewModel()
    {
        return new DashboardViewModel
        {
            LastFed = "unknown",
            WaterTemperatureTile = new SensorTileViewModel
            {
                Title = "Water temperature",
                Value = sensorDataService.GetWaterTemperatureFahrenheit().Value,
                ColorCssClass = "panel-primary",
                IconCssClass = "fa-sliders",
                Url = urlHelper.Action("GetWaterTemperatureChart", "History")
            }
            }
        };
    }
}

DashboardViewModel.cs

public class DashboardViewModel
{ 
    public SensorTileViewModel WaterTemperatureTile { get; set; }
    public SensorTileViewModel FishMotionTile { get; set; }
    public SensorTileViewModel WaterOpacityTile { get; set; }
    public SensorTileViewModel LightIntensityTile { get; set; }
    [Display(Name = "Please enter the food amount:")]
    public int FoodAmount { get; set; }
    [Display(Name = "Last feeding was at: ")]
    public string LastFed { get; set; }
}

public static class ViewModelFactory
{
    public static DashboardViewModel CreateDashboardViewModel()
    {
        return new DashboardViewModel
        {
            LastFed = "unknown",    
            WaterTemperatureTile = CreateSensorTileViewModel()
        };
    }
    public static SensorTileViewModel CreateSensorTileViewModel()
    {
        return new SensorTileViewModel
        {
            Title = "Water temperature",
            ColorCssClass = "panel-primary",
            IconCssClass = "fa-sliders"
        };
    }
}

public class ViewModelService : IViewModelService
{
    private readonly ISensorDataService sensorDataService;
    private readonly IUrlHelper urlHelper;
    public ViewModelService(
               ISensorDataService sensorDataService, 
               IUrlHelperFactory urlHelperFactory, 
               IActionContextAccessor actionContextAccessor)
    {
        sensorDataService = sensorDataService;
        urlHelper = urlHelperFactory.GetUrlHelper(actionContextAccessor.ActionContext);
    }
    public DashboardViewModel GetDashboardViewModel()
    {
        var model = ViewModelFactory.CreateDashboardViewModel();
        var url = urlHelper.Action("GetWaterTemperatureChart", "History")
        var waterTemp = sensorDataService.GetWaterTemperatureFahrenheit().Value;
        model.Value = waterTemp;
        model.url = url;
        return model;
    }
}