Need help with LINQ query and ASP.NET MVC? - asp.net-mvc

My repository returns a list of Accounts.
Each account has a date and a MoneySpent decimal amount. So, I have my list of Accounts and in my controller I'm trying to process this list a little.
I want to have an object which contains the string name of all the months in my Account list and a Sum of all money spent for that month.
Here is what I have tried:
[AcceptVerbs(HttpVerbs.Get)]
public ActionResult Detail(int id)
{
var recentAccounts = accountRepository.GetAccountsSince(DateTime.Now.AddMonths(-6));
var monthlyTotals = from a in recentAccounts
group a by a.DateAssigned.Month.ToString("MMM") into m
select new
{
Month = m.Key,
MonthSum = m.Sum(a => a.MoneySpent)
};
return View();
}
Does this seem like the right way to calculate monthlyTotals?
Also, I've been using strongly typed views with ViewModels for each view, so what type should I make monthlyTotals so I can add it as a field on my ViewModel and pass it to my View?

Looks right to me.
When I need to pass data like this to my view, I create a class for it. So your class would look like this:
public class MonthlyTotal
{
public string Month { get; set; }
public decimal MonthSum { get; set; }
}
and your SELECT clause would look like this:
select new MonthlyTotal
{
Month = m.Key,
MonthSum= m.Sum(a => a.AmountAssigned)
}

I would probably break out that logic into a service layer class holding business logic. Along with that, if the view is expecting a structure different than the model, you would transform your results in your service method returning a custom model type.

Using an anonymous type won't work since the view code won't know what properties it has. I suggest creating a view-only model in the Models directory.
public class MonthlySumModel
{
public string Month { get; set; }
public decimal Sum { get; set; }
}
Then create a new model value in the select statement:
select new MonthlySumModel
{
Month = m.Key,
Sum = m.Sum(a => a.MoneySpent)
};
You can then use this model as the type for the view.

Related

Code reuse in multiple mvc views

I have read this link: https://www.future-processing.pl/blog/view-code-reuse-techniques-in-asp-net-mvc/
I can not use any of those helper ways...
I have to show on multiple mvc sites this string:
1612-1
That is an inquiry number: 16 is the day of month, 12 the month of year and 1 is the database id. I am sure that will not be the final impl but for now we take it as given.
public class MyViewModel
{
public string City { get; set; }
public string PostalCode { get; set; }
public List<string> ActionItemDescriptions { get; set; }
public string InquiryNumber { get; set; }
}
Where would you create the InquiryNumber?
If I put it inside the razor view I cant reuse it.
Seems business logic to me , so it belongs in the business layer.
Then, from within your controller you:
call the business component which returns the inquiry number
store the number in your view model
pass the view model to the view.
One way you could get an inquiry number, without using a helper, is this:
In a controller, have the following action method:
public ActionResult GetInquiryNumber()
{
// TODO : The code to get the inquiry number.
return Content("1612-1");
}
You can then call that method in any view you like, using the following:
#{ Html.RenderAction("GetInquiryNumber", "Home"); }
Obviously you will need to come up with your own method, and controller, names.
This isn't the ideal way of passing data to a view (using a viewmodel is preferable), but the above approach is an option to you.

Editing some properties of View Model in ASP.NET MVC

I'm using Entity Framework Database First approach. Let's say I have a model class called Product and that class has a NumberOfViews property. In the Edit page I pass an instance of the product class to the controller.
The problem is I can't add #Html.EditorFor(model => model.NumberOfViews) in the Edit page, because it's supposed that NumberOfViews is updated with every visit to the product page, and NOT by the website Admin.
And I can't add it as #Html.HiddenFor(model => model.NumberOfViews), because if the Admin Inspected the element, he can edit it manually.
Also If I try to programmatically set the value on the server-side (e.g., Product.NumberOfViews = db.Products.Find(Product.Id).NumberOfViews;), I get the following error:
An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key.
And if I don't add it to either the view or the controller, the value will be null, thus overriding any previous value.
So what should I do?
I have noticed a lot of people use the same model for their Entity Framework as they do for their MVC Controller. I generally discourage this practice. In my opinion, a database model is not the same as a view model.
Sometimes a view needs less information than what the database model is supplying. For example while modifying account password, view does not need first name, last name, or email address even though they may all reside in the same table.
Sometimes it needs information from more than one database table. For example if a user can store unlimited number of telephone numbers for their profile, then user information will be in user table and then contact information with be in contact table. However when modifying user profile, they may want to add/edit/delete one or more of their numbers, so the view needs all of the numbers along with first name, last name and email address.
This is what I would do in your case:
// This is your Entity Framework Model class
[Table("Product")]
public class Product
{
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int ProductId { get; set; }
public string Name { get; set; }
public int NumberOfPageViews { get; set; }
}
// This is the model you will use in your Edit action.
public class EditProductViewModel
{
public int ProductId { get; set; }
public string Name { get; set; }
}
public class ProductController : Controller
{
IProductService service;
//...
[HttpGet]
public ActionResult Edit(int productId)
{
var product = service.GetProduct(productId);
var model = new EditProductViewModel()
{
ProductId = product.ProductId,
Name = product.Name
};
return View(model);
}
[HttpPost]
public ActionResult Edit(EditProductViewModel model)
{
if (ModelState.IsValid)
{
var product = service.GetProduct(model.ProductId);
product.Name = model.Name;
service.Update(product);
}
// ...
}
}

Updating many-to-many relationship entity framework

I have problem with updating entites that have many-to many relationship. Below my User and category class:
public class User : IEntity
{
[Key]
public virtual long Id { get; set; }
private ICollection<Category> _availableCategories;
public virtual ICollection<Category> AvailableCategories
{
get { return _availableCategories ?? (_availableCategories = new List<Category>()); }
set { _availableCategories = value; }
}
}
public class Category : IEntity
{
[Key]
public long Id { get; set; }
/// <summary>
/// Full name or description of a category
/// </summary>
[StringLength(255)]
public string FullName { get; set; }
}
This is code snippet from my repository
public override void Edit(User user)
{
var dbUser = _context.Users.Include(x => x.AvailableCategories)
.Single(x => x.Id == user.Id);
var categories = _context.Categories;
dbUser.AvailableCategories.Clear();
foreach (var cat in user.AvailableCategories)
{
dbUser.AvailableCategories.Add(cat);
}
_context.Entry(dbUser).State = EntityState.Modified;
}
However the categories don't get updated. What EF does is insert empty rows into category table and sets relations to this new rows with user.
How can I update User so that I change only categories that already exist in the database?
User that I pass to Edit method has AvailableCategories with only Ids set (rest of properties are empty).
When you're doing something like posting back M2M relationships, you either must post the full object, as in every single property on those objects, or simply post a list of ids and then use those to query the associated objects back from the database. Otherwise, Entity Framework understands your purpose to be to update the properties on the objects as well, in this case with empty values.
Obviously the first option is quite unwieldy, so the second way is the preferred and standard way. Generally, for this, you'd want to use a view model so you could have a property like the following, that you would post into:
public List<long> SelectedCategories { get; set; }
But, if you insist on using the entity directly, you can get much the same result by simply doing:
var selectedCategories = user.AvailableCategories.Select(m => m.Id)
Once you have the ids:
var newAvailableCategories = _context.Categories.Where(m => selectedCategories.Contains(m.Id));
And then finally set that on your user:
dbUser.AvailableCategories = newAvailableCategories;
I notice you are also adding the user.AvailableCategories directly into dbUser.AvailableCategories. I've noticed when binding back complex objects from an MVC view that DB Entities are no longer attached to the DbContext. If you look at the entity, you can verify by checking dbContext.Entry(cat).State is "detached" (or something unexpected) I believe.
You must query those entities back out of the dbContext (possibly by using the returned cat.Id's). Or otherwise manually set the entities as "unchanged". And then add those "non-detached" items into dbUser.AvailableCategories. Please see Chris's answer as it shows with specific code how to get this done.
Also, I might use a linking entity. Possibly something like this:
public class UserCategory
{
public User User {get;set;}
public Category Category {get;set;}
}
And add it to DB context. Also, drop the linking lists in your current User and Category class. This way you can manipulate the UserCategory class (and DbSet) to manage your many-to-many relationship.

ASP.NET MVC Webgrid display multiple columns in a single row

I have a Asp.net MVC grid.
My problem is I need to display multiple columns in a single row.
For example:
Name Date Compensation
Id USD - 99999
Grade INR - 99999
The above layout is a single row in the grid.
All the columns (Name, Id, Grade, Curency1, Amount1, Currency2, Amount2 ) are available in a single record as separate columns. Here Currency1 means USD and Currency2 means INR.
Any ideas how to do this. I am using a strongly typed model and EF6.
I think the best way to do this would be to create a separate 'type' and model for each multi-faceted column, then try to display this type in the webgrid (which I show is possible in the latter part of my example).
For example:
Create a new 'type' (or 'column') class called CompensationColumn:
...
using System.Web.Mvc;
namespace yourproject.Columns // I put this in its own namespace/folder - you don't have to
{
public class CompensationColumn
{
public string Currency1 { get; set; }
public int Amount1 { get; set; }
public string Currency2 { get; set; }
public int Amount2 { get; set; }
public CompensationColumn(string currency_1, int amount_1, string currency_2, int amount_2)
{
Currency1 = currency_1;
Amount1 = amount_1;
Currency2 = currency_2;
Amount2 = amount_2;
}
}
}
Then create a file called CompensationColumn.cshtml in the yourproject/Shared/EditorTemplates folder (if the Shared folder doesn't exist you can also create a your view/DisplayTemplates folder). Define how this column will look, as if it was a custom 'type' (modify this to your liking):
#model yourproject.Columns.CompensationColumn
#if (Model != null)
{
#Model.Currency1<text> - </text>#Model.Amount1<text><p/></text>
#Model.Currency2<text> - </text>#Model.Amount2
}
else
{
}
Then in your Models folder, create a partial class to extend your current EF table model (file name shouldn't matter). I am going to assume your table is 'employee_table'. I am also adding Metadata for the model in this class as it is a good place to put it if you are using a database-first design:
using System.Web.Mvc;
using yourproject.Columns;
namespace yourproject.Models
{
[MetadataType(typeof(EmployeeModelMetaData))] // This links the metadata class below
public partial class employee_table // This should be the EF class name
{
[DisplayName("Compensation")]
public CompensationColumn Compensation { get; set; } // Here we add a new field for your row
}
public class EmployeeModelMetaData
{
// copy your EF class fields here and decorate them with dataannotations. This is helpful
// if you are using a database-first design as it won't get overwritten when db changes.
[DisplayName("Id")]
public int emp_id { get; set; }
[DisplayName("Amount")]
[DisplayFormat(DataFormatString = "{0:c}", ApplyFormatInEditMode = true)]
public int emp_amount1 { get; set; }
// etc . . .
}
}
I make a few assumptions here about a database-first design, but you should be able to figure out how to adapt it to a code-first design if needed.
If you also need to edit elements this column type together, then you would need to create a model binder, but I'm not going there since you only mentioned displaying it.
To get the display template to display in the webgrid, you will need to format: the columns of the webgrid. In your view with an IEnumerable model (e.g. your Index view):
#{
var grid = new WebGrid(Model);
List<WebGridColumn> columns = new List<WebGridColumn>();
WebGridColumn col = grid.Column(columnName: "Col3", header: "Compensation", format: (item) =>
{
yourproject.Columns.CompensationColumn c = item.Compensation; return Html.DisplayFor(model => c);
} );
columns.Add(col);
}
#grid.GetHtml(columns: columns)
This last snippet I adapted from Frédéric Blondel's code here

ASP.NET MVC - Partially updating model from view

I just wondered how people were approaching this situation. It's something that seems like a weak point in my usage of MVC with ORMs (NHibernate in this case)...
Say you have a fine-grained and complicated entity in your model. You will likely have an admin page to manage objects of this type. If the entity is complicated, it is unlikely that you will be modifying the whole entity in one form. You still need to pass the relevant properties to the view, and incorporate changes to those properties in the model when the view returns them.
What does anyone do in this situation?
Create a view model which is (or contains) a subset of the entities properties. Pass this to and from the view. In 'edit' action method in controller, get the object from repository, go though all the properies in the ViewModel and apply them to the Model object (model.a = viewmodel.a, modelb = viewmodel.b). This seems the obvious sensible route, but generates a lot of tedious plumbing code. Also this complicates validation a bit.
Something else?
I've looked briefly at automapper - but this doesn't seem to fit the bill exactly, maybe I'm wrong?
Thanks.
This sounds like the perfect scenario for automapper. You create a view model class which contains a subset of the fields or your real model, and you let AutoMapper take care extraccting values from the domain model object into your view model object. What issues are you having with this approach?
Consider this example:
Here is your domain model and your view model
public class Person
{
public string FirstName
{ get; set; }
public string LastName
{ get; set; }
public string HomeNumber
{ get; set; }
public string Address1
{ get; set; }
public string Address2
{ get; set; }
}
public class PersonViewModel
{
public string FirstName
{ get; set; }
public string LastName
{ get; set; }
public string HomeNumber
{ get; set; }
}
Here is your mapping, you have to create a mapping in both directions from dm->vm and vm->dm.
From what I've seen when using Automapper is that if you map from object A to B and B has a property which A doesn't have, it will be reset. So when I create the map I direct it to ignore those missing properties. I'm not a Automapper expert so I may be using it wrong.
Mapping
Mapper.CreateMap<Person, PersonViewModel>();
// Automapper will reset values in dest which don't exist in source, so be sure to ignore them!
Mapper.CreateMap<PersonViewModel, Person>()
.ForMember(dest => dest.HomeNumber, opt => opt.Ignore());
Finally usage:
Person p = new Person()
{
FirstName = "First",
LastName = "Last",
Address1 = "add 1",
Address2 = "add 2"
};
PersonViewModel pvm = Mapper.Map<Person, PersonViewModel>(p);
// Map to a new person
Person p2 = Mapper.Map<PersonViewModel, Person>(pvm);
// Map to the existing person just to update it
Person p3 = new Person()
{
HomeNumber = "numberHere"
};
// This will update p3
Mapper.Map<PersonViewModel, Person>(pvm, p3);
Because of the exclusion, this is obviously less than ideal, but much better than manually doing the whole thing.
Have your view model map one-to-one with your domain model.
Specify Model as argument for the routeValues as below. This means your view model will be initialized with the values from the domain model. Only the sub set of fields in the form will be overwritten in the resulting personViewData.
Update View:
#model ViewModel.PersonView
#using (Html.BeginForm("Update", "Profile", Model, FormMethod.Post))
{
...Put your sub set of the PersonView fields here
}
ProfileController:
public ActionResult Update(string userName)
{
Person person = _unitOfWork.Person.Get().Where(p => p.UserName == userName).FirstOrDefault();
PersonView personView = new PersonView();
Mapper.Map(person, personView);
return View(personView);
}
[HttpPost]
public ActionResult Update(PersonView personViewData)
{
Person person = _unitOfWork.Person.Get().Where(p => p.UserName == personViewData.UserName).FirstOrDefault();
Mapper.Map(personViewData, person);
_unitOfWork.Person.Update(person);
_unitOfWork.Save();
return Json(new { saved = true, status = "" });
}
Why don't you use TryUpdateModel with the form collection.
If your view is editing a person
public class Person
{
public string ID { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string Email { get; set; }
public string Address { get; set; }
}
And your view is only editing first name and last name, you can do this:
public ActionResult Action(FormCollection form)
{
Person personToUpdate = Repository.GetPerson(form["ID"]);
TryUpdateModel<Person>(personToUpdate, form);
Repository.Update(personToUpdate)
return View();
}
That will only update Person with the items that a part of the form collection. If you don't want a field updated, don't submit it with the form.
What if you have full model but each page uses and updates only the required part? Then you update the business model using complete view data at the last page.
I use a similar approach to yours (in my case Entity Framework) with Entity -> ViewModel -> View but only on views with "complex" entities that have either 1:M or M:M relationships. In most cases I took the low road and went for Entity->View when I have a simple entity.
My ViewModel is defined as Entity+supporting properties: SelectList or MultiSelectList and either a string or List<string>. I'll also use a ViewModel for instances where I have properties I need for the view but may not necessarily need in the entity (database).
Http Get controller methods are straightforward ActionResults with return View(repository.FetchNewViewModel()) for Create or repository.FetchModelById(id) for Edit. In both instances I'm initializing my entities before passing them to the view.
Create([Bind(Exclude = "Entity.EntityId")] ViewModel model) and Edit(ViewModel model) are the Http Post controller methods of Create and Edit. My Edit view has a hidden input field for EntityId to pass it back and forth.
By the time the Http Post method has the viewmodel, I lose all Entity.Relation and ViewModel.(Multi)SelectList values. I have to rebuild the object if I want my view to display properly:
`
try
{
var tags = model.TagIds; // List<string> or <int> depending on your Id type
if (model.TagsList == null) // It will be
{
model.TagsList = _repository.FetchSelectedTags(tags); // Build a new SelectList
}
if (!ModelState.IsValid)
{
return View(model);
}
_repository.Add(model.Article, tags); // or Save() for Edit
}
catch
{
return View(model); // Generally means something screwed in the repository class
}
return RedirectToAction("Index");
`
There is maybe 30% of my entity base using a ViewModel so I definitely only use it as needed. If you have complex views and model data in most instances you can probably break it down to smaller views.
Right now i´m working on a large project using S#arp Architecture and im also using the approach:
Model -> ViewModel -> Model
I use the ViewModel for the Binding part and Validations, the other approach is to use the Model Directly (with tryUpdateModel / UpdateModel which we used during the prototype develop) but for complex scenarios we end up handling special situation like SelectLists/Checkbox/Projections/HMAC Validations in a little ViewModel anyway and using a lot of Request.Form["key"] =( , the other drawback is handling the errors situations where you want to repopulate the form with the user input, i found it a little more complicated using the Model directly (using a ViewModel we take a lot of advantage of ModelState attempted value, saving us a couple of trips to the DB, anyone who have faced this scenario will know what i mean).
This approach is a bit time consuming, just like you said, you end up matching properties, but in my opinion is the way to go for complex forms.
It worth mentioning that we just use ViewModels for the Create/Edit scenarios, for almost everything else we use directly the model.
I have not use autommapers so far, but definitely i ll give it a try.

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