下面是我的最佳实践代码片段:

    public class UserController : Controller
    {
        private readonly IUserService userService;
        private readonly IBuilder<User, UserCreateInput> createBuilder;
        private readonly IBuilder<User, UserEditInput> editBuilder;

        public UserController(IUserService userService, IBuilder<User, UserCreateInput> createBuilder, IBuilder<User, UserEditInput> editBuilder)
        {
            this.userService = userService;
            this.editBuilder = editBuilder;
            this.createBuilder = createBuilder;
        }

        public ActionResult Index(int? page)
        {
            return View(userService.GetPage(page ?? 1, 5));
        }

        public ActionResult Create()
        {
            return View(createBuilder.BuildInput(new User()));
        }

        [HttpPost]
        public ActionResult Create(UserCreateInput input)
        {
            if (input.Roles == null) ModelState.AddModelError("roles", "selectati macar un rol");

            if (!ModelState.IsValid)
                return View(createBuilder.RebuildInput(input));

            userService.Create(createBuilder.BuilEntity(input));
            return RedirectToAction("Index");
        }

        public ActionResult Edit(long id)
        {
            return View(editBuilder.BuildInput(userService.GetFull(id)));
        }

        [HttpPost]
        public ActionResult Edit(UserEditInput input)
        {           
            if (!ModelState.IsValid)
                return View(editBuilder.RebuildInput(input));

            userService.Save(editBuilder.BuilEntity(input));
            return RedirectToAction("Index");
        }
}

下面是我的最佳实践代码片段:

    public class UserController : Controller
    {
        private readonly IUserService userService;
        private readonly IBuilder<User, UserCreateInput> createBuilder;
        private readonly IBuilder<User, UserEditInput> editBuilder;

        public UserController(IUserService userService, IBuilder<User, UserCreateInput> createBuilder, IBuilder<User, UserEditInput> editBuilder)
        {
            this.userService = userService;
            this.editBuilder = editBuilder;
            this.createBuilder = createBuilder;
        }

        public ActionResult Index(int? page)
        {
            return View(userService.GetPage(page ?? 1, 5));
        }

        public ActionResult Create()
        {
            return View(createBuilder.BuildInput(new User()));
        }

        [HttpPost]
        public ActionResult Create(UserCreateInput input)
        {
            if (input.Roles == null) ModelState.AddModelError("roles", "selectati macar un rol");

            if (!ModelState.IsValid)
                return View(createBuilder.RebuildInput(input));

            userService.Create(createBuilder.BuilEntity(input));
            return RedirectToAction("Index");
        }

        public ActionResult Edit(long id)
        {
            return View(editBuilder.BuildInput(userService.GetFull(id)));
        }

        [HttpPost]
        public ActionResult Edit(UserEditInput input)
        {           
            if (!ModelState.IsValid)
                return View(editBuilder.RebuildInput(input));

            userService.Save(editBuilder.BuilEntity(input));
            return RedirectToAction("Index");
        }
}

就我个人而言，我建议如果ViewModel不是微不足道的，那么使用一个单独的类。

如果你有多个视图模型，那么我建议至少在一个目录中划分它。如果稍后共享视图模型，则目录中隐含的名称空间可以更容易地移动到新的程序集。

ViewModel类用于将由类实例表示的多个数据封装到一个易于管理的对象中，您可以将该对象传递给View。

将ViewModel类放在自己的文件中，放在自己的目录中是有意义的。在我的项目中，我有一个名为ViewModels的Models文件夹子文件夹。这就是我的ViewModels(例如ProductViewModel.cs)所在的位置。

创建一个视图模型基类，它具有通常需要的属性，如操作结果和上下文数据，您还可以放置当前用户数据和角色

class ViewModelBase 
{
  public bool HasError {get;set;} 
  public string ErrorMessage {get;set;}
  public List<string> UserRoles{get;set;}
}

在基控制器类中，有一个类似PopulateViewModelBase()的方法，该方法将填充上下文数据和用户角色。 HasError和ErrorMessage，如果从service/db中提取数据时出现异常，请设置这些属性。在视图上绑定这些属性以显示错误。 用户角色可用于根据角色在视图中显示隐藏部分。

要在不同的get操作中填充视图模型，可以通过具有具有抽象方法FillModel的基本控制器使之一致

class BaseController :BaseController 
{
   public PopulateViewModelBase(ViewModelBase model) 
{
   //fill up common data. 
}
abstract ViewModelBase FillModel();
}

在控制器

class MyController :Controller 
{

 public ActionResult Index() 
{
   return View(FillModel()); 
}

ViewModelBase FillModel() 
{ 
    ViewModelBase  model=;
    string currentAction = HttpContext.Current.Request.RequestContext.RouteData.Values["action"].ToString(); 
 try 
{ 
   switch(currentAction) 
{  
   case "Index": 
   model= GetCustomerData(); 
   break;
   // fill model logic for other actions 
}
}
catch(Exception ex) 
{
   model.HasError=true;
   model.ErrorMessage=ex.Message;
}
//fill common properties 
base.PopulateViewModelBase(model);
return model;
}
}

There are no good place to keep your models in. You can keep them in separate assembly if the project is big and there are a lot of ViewModels (Data Transfer Objects). Also you can keep them in separate folder of the site project. For example, in Oxite they are placed in Oxite project which contains a lot of various classes too. Controllers in Oxite are moved to separate project and views are in separate project too. In CodeCampServer ViewModels are named *Form and they are placed in UI project in Models folder. In MvcPress project they are placed in Data project, which also contains all code to work with database and a bit more (but I didn't recommend this approach, it's just for a sample) So you can see there are many point of view. I usually keep my ViewModels (DTO objects) in the site project. But when I have more than 10 models I prefer to move them to separate assembly. Usually in this case I'm moving controllers to separate assembly too. Another question is how to easily map all data from model to your ViewModel. I suggest to have a look at AutoMapper library. I like it very much, it does all dirty work for me. And I also I suggest to look at SharpArchitecture project. It provides very good architecture for projects and it contains a lot of cool frameworks and guidances and great community.