试着围绕包括EF / DbSET的复杂模型

Question

I'll try again to explain (different example / names of things than in my OP).

Database:

public partial class My_db : DbContext
{
    public My_db()
        : base("name=My_db")
{
}
public DbSet<LGDetail> LGDetails { get; set; }

 }

The model (subfile of a .edmx / .tt ):

enter  public class LGDetail
{
    public int ID { get; set; }
    public string CUSTOMERID { get; set; }
    public string PropertyID { get; set; }
    public string CampaignID { get; set; }
    public string Notes { get; set; }
    // other properties snipped
} 

In the controller - returns the results of any matching records where PropertyID is same as the ?findByString=xxx param in the url.

public ActionResult LinkedDetails(string findByString)
    {
        var findPropertyID = "";
        if (findByString != null)
        {
            findPropertyID = findByString;
        }
        var lgdetail = db.LGDetails
             .OrderBy(r => r.PropertyID)
             .Where(r => r.PropertyID == findPropertyID);

        if (lgdetail == null)
        {
            return HttpNotFound();
        }
        return View(lgdetail);
    }

the view LinkedDetails:

  @model IEnumerable<MyProject.LGDetail>

  @foreach (var item in Model)
 {

    @Html.DisplayFor(modelItem => item.CUSTOMERID)<BR>
@Html.DisplayFor(modelItem => item.PropertyID)<BR>
// plus whatever other things from that specific table I want to display
  }

Ok, all of this works fine. What I continue to not understand, after close to a week of looking at google for hours a day, is how do you "break out" of this constrained methodology?

Stream of consciousness questions:

@foreach (var item in Model) only seems to work as long as I have this: @model IEnumerable If I change it to @model MyProject.LGDetail, then what do you do to display the results of the query? I keep getting the error: MyProject.LGDetail does not contain a public definition for 'GetEnumerator'

From my original question:

 public class MyModel2 
 {
  public string namesCombined { get; set; }
  public int theAge { get; set; }
 }

MyModel2 is NOT anything to do with the table / model LGDetail. Let's pretend I queried a totally different table with some other criteria and got back a whole different set of results. So now I have two sets of results that I want to display in the SAME view.

HOW do you do that? How do you pass two models to the same view and loop through the results of each one in SEPERATE areas of the same view?

What if there was a third model with static info that didn't even come from a database?

Answer 1

What I am having trouble wrapping my head around is how a view can only take data from one model at a time. In this case, the model in question only has database fields.

I also had this problem when I was starting to learn MVC. In a nutshell, use a ViewModel . A view model can be a combination of fields that came from different models altogether. You're still sticking to the principle that there is one view and one model. What you need to know is that you can create the "combined" model (or simply, the viewmodel) in the controller.

In your case:

public class LGCustDataViewModel
{
    // ------------- this is from LGCustData model
    public string LastName { get; set; }
    public string FirstName { get; set; }
    public DateTime BirthDate { get; set; }
    // ------------- this is from LGCustData model

    // ------------- this is just manipulation of data within this model
    public string namesCombined 
    { 
        get
        {
            return FirstName + " " + LastName;
        }
    }
    public int theAge 
    { 
        get
        {
             return -1;
             //DateTime.Now.Year - BirthDate.Year
        }
    }
    // ------------- this is just manipulation of data within this model

    // ------------- this came from another model, like LoginAccount
    public string Username { get; set; }
    public string Password { get; set; }
    // ------------- this came from another model, like LoginAccount
}

Then in your view, you'll be using that viewmodel like

@model MyProject.LGCustDataViewModel

The tricky part or where most discussions are will be on the controller. Others think that the controller should be as thin/small as possible but others argue that its ok to have the following code on the controller:

public ActionResult Details(int CustomerID)
{
    //simplified for brevity

    //get from LGCustDatas
    LGCustData custData = dbContext.LGCustDatas.GetByCustomerID(CustomerID);

    //get from LGCustLogins model
    var custLogin = dbContext.LGCustLogins.GetByCustomerID(CustomerID);


    //You can 'combine' models via a view model
    var custDataVM = new LGCustDataViewModel();
    custDataVM.LastName = custData.LastName;
    custDataVM.FirstName = custData.FirstName;
    custDataVM.BirthDate = custData.BirthDate;

    custDataVM.UserName = custLogin.UserName;
    custDataVM.Password = custLogin.Password;

    return View(custDataVM);
}

Using view models allows you to isolate the presenation layer (views) from any underlying changes in your domain model. In our example, the view doesn't really need to know where UserName and Password fields came from.

UPDATE:

If you want to have a list of customers, you can still do that using viewmodels. In your view:

@model IEnumerable<MyProject.LGCustDataViewModel>

Then in your controller:

public ActionResult Index()
{
    //simplified for brevity

    //get from LGCustDatas
    List<LGCustData> custData = dbContext.LGCustDatas.GetAllCustomers();

    var listCustomer = new List<LGCustDataViewModel>();

    foreach(customer in LGCustData)
    {
        //You can 'combine' models via a view model

        var custDataVM = new LGCustDataViewModel();
        custDataVM.LastName = customer.LastName;
        custDataVM.FirstName = customer.FirstName;
        custDataVM.BirthDate = customer.BirthDate;

        //get from LGCustLogins model
        var custLogin = dbContext.LGCustLogins.GetByCustomerID(customer.CustomerID);

        custDataVM.UserName = custLogin.UserName;
        custDataVM.Password = custLogin.Password;

        listCustomer.Add(custDataVM);
    }
    return View(listCustomer);
}

EDIT after OP's edit/update:

@foreach (var item in Model) only seems to work as long as I have this: @model IEnumerable If I change it to @model MyProject.LGDetail, then what do you do to display the results of the query? I keep getting the error: MyProject.LGDetail does not contain a public definition for 'GetEnumerator'

After changing it to @model MyProject.LGDetail you can do this in your view without the foreach loop:

@Html.DisplayFor(model => model.CUSTOMERID)<BR>
@Html.DisplayFor(model => model.PropertyID)<BR>

You may also want to add a .FirstOrDefault() after .Where(r => r.PropertyID == findPropertyID) in LinkedDetails() method so that it becomes

var lgdetail = db.LGDetails
         .OrderBy(r => r.PropertyID)
         .Where(r => r.PropertyID == findPropertyID).FirstOrDefault();

Let's pretend I queried a totally different table with some other criteria and got back a whole different set of results. So now I have two sets of results that I want to display in the SAME view. HOW do you do that? How do you pass two models to the same view and loop through the results of each one in SEPERATE areas of the same view?

Imagine all the properties in LGDetail , MyModel2 and a third model with static info that didn't even come from a database are all combined in a big class. That big class is the viewmodel and that's what you'll use in your view. Instead of

@model MyProject.LGDetail

it should be

@model MyProject.LGDetailViewModel

Like let's say this is in MyModel3: public string Username { get; set; }. So now there's information from two tables populating two different models that each require their own loop as well as a third piece requiring no loop. This is what I just don't get.

Ok so here are your models:

public class MyModel3
{
    public string Username {get; set;}
}

public class LGDetail
{
    public int ID { get; set; }
    public string CUSTOMERID { get; set; }
    public string PropertyID { get; set; }
    public string CampaignID { get; set; }
    public string Notes { get; set; }
    // other properties snipped
} 

And this would be your ViewModel :

public class LGCustDataViewModel
{
    public string Username {get; set;}

    public IEnumerable<LGDetail> LGDetailList { get; set; }
}

In your controller, you'll need to load up the LGDetailViewModel with the values from the other 3 domain models.

public ActionResult MyView()
{
    List<LGDetail> lgDetailList = dbContext.LGCustDatas.GetAllCustomers();                  

    var viewModelObj = new LGDetailViewModel();

    viewModelObj.LGDetailList = lgDetailList;

    viewModelObj.Username = "whatever";
}

In your view use this

@model MyProject.LGDetailViewModel

@Html.DisplayFor(model => model.Username)
@foreach(var record in Model.MyModel2)
{
    @Html.DisplayFor(model => item.namesCombined)
}

@foreach(var record in Model.MyModel3)
{
    @Html.DisplayFor(model => item.CUSTOMERID)
}