Develop Reference

Populating ViewModel

I've been searching all over the web to find an answer for such simple question, but I can't seem to find one.
Suppose we have a Product that has an edit page where we can set name, price and category.
Following the MVC(MVVM) pattern we have:
2 models ProductModel and ProductCategoryModel
ViewModel that holds the product and the categories list (for the dropdown)
View to display the edit page
Beside the above we have the ProductService which handles the CRUD operations
// Model
public class ProductModel
{
public int ProductId { get; set; }
public string Name { get; set; }
public decimal Price { get; set; }
public int CategoryId { get; set; }
}
// Model
public class ProductCategoryModel
{
public int CategoryId { get; set; }
public string Name { get; set; }
}
// ViewModel
public class EditProductViewModel
{
public ProductModel Product { get; set; }
public List<ProductCategoryModel> Categories { get; set; }
}
The question is who is responsible for populating the ViewModel? I though it could be done in the constructor of the view model, however people say it is bad practice. Populating it in the controller also doesn't seems right.

You will map your EditProductViewModel from your ProductModel/ProductCategoryModel in the page controller.
You can then call your action to render your html page and pass your viewModel object.
Something like this :
public class HomeController : Controller
{
private EditProductViewModel viewModel;
public HomeController()
{
this.viewModel = new EditProductViewModel();
InitialiseViewModel();
}
public ActionResult Index()
{
return View("Index", viewModel);
}
private void InitialiseViewModel()
{
ProductCategoryModel productCategoryModel = new ProductCategoryModel();
ProductModel productModel = new ProductModel();
//do your mapping
productModel.Name = "Test mapping";
this.viewModel.Product = productModel;
}
}
Your .cshtml will look like this
#model WebApplication5.ViewModels.EditProductViewModel
<div class="jumbotron">
<h1>ASP.NET</h1>
<p>#Model.Product.Name</p>
<p class="lead">ASP.NET is a free web framework for building great Web sites and Web applications using HTML, CSS and JavaScript.</p>
<p>Learn more »</p>
</div>

Pass parameter from Htmldropdownlistfor to controller

I have a model passed from controller to view in my asp.net mvc5 website. Then I show the dropdownlist using the model and I want to pass an id back when submitting the form. Here is my model :
public class SiteDirectionModel
{
public int id { get; set; }
public string name { get; set; }
}
Then in the model, I use a List<SiteDirectionModel> to which I add new instances of each item I need. I fill up both these lists and then pass my model to the view.
#model List<SiteDirectionModel>
#using (Html.BeginForm("GetSiteRF", "Create", FormMethod.Post))
{
#Html.DropDownListFor(x => x.name,new SelectList(Model.name,"Sites"));
<input type="button" value="Selectionner" class="btn btn-primary"/>
}
Then how to retrieve the ids for each name ? And how to pass it as a parameter to my controller? Such that I would have :
public ActionResult GetSiteRF(int id)
{
int newId = id;
//Call method to searchId ...
return View("CreateADUser");
}

I have given how to bind and get value from dropdown. Please use your own BL in this.
Your model should be like this.
public class Something
{
public int Id { get; set; }
public string Name { get; set; }
}
public class SiteDirectionModel
{
public SelectList MyDropDown { get; set; }
public int SelectedValue { get; set; }
}
You BL should be like this.
public List<Something> GetListofSomething()
{
//your logic.
}
Your Get method should be like this.
public ActionResult MyGetMethod()
{
SiteDirectionModel model = new SiteDirectionModel();
model.MyDropDown = new SelectList(GetListofSomething(), "key_field_name", "value_field_name", "default_value");
}
Then finally HTML
#Html.DropDownListFor(x => x.SelectedValue,Model.MyDropDown)

MVC 5 Help Understanding ViewModel

Okay, so i have my ViewModel and I understand what the controller does, I'm just having difficulty implementing it. I don't know how to code a controller for the ViewModel, i've tried researching it myself and can't find anything.
Here is my viewModel, how would I go about constructing the controller? Not asking you to do it for me, just how to do it
public class ViewOrderViewModel
{
//From ORDER Table
public int OrderId { get; set; }
public System.DateTime OrderDate { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string Address { get; set; }
public string City { get; set; }
public string PostalCode { get; set; }
public string Country { get; set; }
public string Email { get; set; }
public decimal Total { get; set; }
//from Products
public List<Product> Products { get; set; }
}
UPDATE
public class ViewOrderController : Controller
{
// GET: ViewOrder
public ActionResult ViewOrders()
{
var order = new Order();
var viewModel = GetViewModel(order);
return View(viewModel);
}
public ViewOrderViewModel GetViewModel(Order orderObject)
{
ViewOrderViewModel viewModel = new ViewOrderViewModel();
viewModel.OrderId = orderObject.OrderId;
viewModel.OrderDate = orderObject.OrderDate;
viewModel.FirstName = orderObject.FirstName;
viewModel.LastName = orderObject.LastName;
viewModel.City = orderObject.City;
viewModel.Address = orderObject.Address;
viewModel.Country = orderObject.Country;
viewModel.Email = orderObject.Email;
viewModel.PostalCode = orderObject.PostalCode;
viewModel.Total = orderObject.Total;
return viewModel;
}
}
Still unsure about how to map the List of products in the ViewModel class to the list of products in the db

Typically, your view is going to be "bound" to the ViewModel. It's like saying "Ok, I'm the view for an 'Order' and I only need to worry about the properties that you defined in ViewOrderViewModel".
The controller is not required for that binding to happen. The binding is declared at the top of your view:
Order.cshtml
#Model MyProject.Web.ViewModels.ViewOrderViewModel
<div>
<!-- Html for the view-->
</div>
This allows you to access properties on that model within the view. Razor has some functions that make life easy. For example, if you want to display the OrderId it might look like this:
<span>OrderId: #Model.OrderId </span>
The view doesn't care what values are set for each of those properties, it only cares that the properties exist. Where the controller comes into play is populating those properties with the values you want and then passing the ViewModel to the view:
public ActionResult Order()
{
var viewModel = new ViewOrderViewModel();
// Load data into each property
viewModel.OrderId = 123; // etc..
// Return it to the view. Asp.net knows to return
// it to the Order.cshtml view because the view
// and the controller action share the same name.
return View(viewModel);
}
Edit: In response to your questions in the comments: If you need to populate your ViewModel with values from a different model (such as a database model) you can create a mapper like so:
public ViewOrderViewModel GetViewModel(Order orderObject)
{
ViewOrderViewModel viewModel = new ViewOrderViewModel();
viewModel.OrderId = orderObject.OrderId;
viewModel.FirstName = orderObject.FirstName;
// etc...
return viewModel;
}
and then in your controller you would do something like this:
// var order = new Order()
var viewModel = GetViewModel(order);

How to populate an array in side a model for postback

I have a model that contains a List of Milestone, I want that list to be populated (inside the model) with a given set of Textboxes in the webpage.
public class Project
{
public string ProjectNumber { get; set; }
public IList<Parameter> Parameters;
public IList<Milestone> MilestoneList = new List<Milestone>();
}
And inside my Html.BeginForm("Edit", "Home", FormMethod.Post, new { Project = Model })) I have the following TextBox.
#for (int i = 0; i < Model.MilestoneList.Count; i++)
{
<td style="align-content: center;">#Html.TextBoxFor(model=>model.MilestoneList[i].Value)</td>
}
My problem in my controller below the milestonelist is always null in model Project
[HttpPost]
public ActionResult Edit(Project project)
{
helper.CreateProject(project, System.Web.HttpContext.Current.User.Identity.Name);
return View();
}
So how should I program so the list inside the model will be populated through TextBoxes?

Your using fields in the model, not properties, so the DefaultModelBinder cannot set the value. Change you model to
public class Project
{
public string ProjectNumber { get; set; }
public IList<Parameter> Parameters { get; set; }
public IList<Milestone> MilestoneList { get; set; }
}
and initialize the collection in in the controller.

How to pass multiple model in view in ASP.NET MVC?

Problem is: I want to run 3 different actions but instead of that i want to fed all data from single action in a bigger model.
I am using:
public class SearchScrapClass
{
public WClass WClass { get; set; }
public SClass SClass { get; set; }
public YClass YClass { get; set; }
}
public class WClass
{
public string title { get; set; }
public string link { get; set; }
}
public class SClass
{
public string title { get; set; }
public string link { get; set; }
}
public class YClass
{
public string title { get; set; }
public string link { get; set; }
}
I am using LINQ to add data in these models.
I am using :
var wikians = from info in document.DocumentNode.SelectNodes("//div[#id='span']")
from link in info.SelectNodes("div//a").Where(x => x.Attributes.Contains("href"))
select new SearchScrapClass //Main Bigger Class
{
WClass.link= link.Attributes["href"].Value, //ERROR: How to add to WClass's url ?
WClass.title= link.InnerText //ERROR: How to add to WClass's url ?
}
var wikians = from info in document.DocumentNode.SelectNodes("//div[#id='results']")
from link in info.SelectNodes("p//a").Where(x => x.Attributes.Contains("href"))
select new SearchScrapClass //Main Bigger Class
{
YClass.link= link.Attributes["href"].Value, //ERROR: How to add to YClass's url ?
YClass.title= link.InnerText //ERROR: How to add to YClass's url ?
}
//Also for the 3rd class (model)
return View(wikians); //and then return bigger class model so that i can access them in view
This is one way i want to add data to link and title of all the classes.
My try is to add data to all 3 classes from different sources and pass the bigger model to view so that i can access all the classes as:
#model SearchScrapClass
#using(Html.BeginForm()) {
#Html.EditorFor(o => o.WClass.link)
...
}
Please suggest a way
Thanks

To Expand on my comment, I would suggest creating a ViewModel folder for organization sake. in this add the view model
public class SearchScrapClassViewModel
{
SearchScrapClass searchScrap;
WClass wClass;
SClass sClass;
YClass yClass;
}
In your controller then you instantiate the new viewmodel
SearchScrapClassViewModel model = new SearchScrapClassViewModel
{
....add in your logic to fill your class objects here
}
return view(model);
then in your view add the using for the viewmodel.
#using SearchScrapClassViewModel

You can pass multiple model by creating a new model class which will contain multiple objects.
public class MultiModel
{
SearchScrapClass searchScrap;
WClass wClass;
SClass sClass;
YClass yClass;
}

See the tuple tutorial http://www.dotnetperls.com/tuple or this one http://msdn.microsoft.com/en-us/library/system.tuple(v=vs.110).aspx
Like controller:
public class HomeController : Controller
{
public ActionResult Index()
{
var first = new FirstModel();
var second = new SecondModel();
return View(Tuple.Create(first,second));
}
}
And the view:
#model Tuple
<div>
#Model.Item1.FirstModelProp
#Model.Item2.SecondModelProp
</div>

SearchScrapClassViewModel model = new SearchScrapClassViewModel
{
....add in your logic to fill your class objects here
}
what logic we apply here " ....add in your logic to fill your class objects here"