How to make simple calculations using model items and an input from a form in ASP.net MVC 3?

Question

Am new to programming and ASP.net MVC 3 so don't be surprised by my lack of knowledge on this.. Okay, I want to multiply two decimals, One decimal comes from the form that a user fills and the other decimal comes from the Model class (gets it from the database).

I have two Model classes called RATE & PROJECTMATERIAL . The RATE class has an item called Amount that states the amount of a Rate and the PROJECTMATERIAL class has an item quantity. The classes are related and i want to be able to say variable1 = quantity*Rates.amount and return variable1 to the my Index, Delete, Details views. I don't want to store variable1 to my database but i just want to display in my views.....but i don't know how and where to do it

Code from Project material class..

public class ProjectMaterial
{
    public int ProjectMaterialID { get; set; }

    [Required]
    [Display(Name = "Scope Name")]
    public int? ScopeID { get; set; }

    [Required]
    [Display(Name = "Rate Code")]
    public int? RateID { get; set; }

    [Required]
    [Display(Name = "Quantity")]
    public decimal Quantity { get; set; }


    public virtual Scope Scopes { get; set; }
    public virtual Rate Rates { get; set; }

}

Code from scope class..

public class Rate
{
    public int RateID { get; set; }


    [Required]
    [Display(Name = "Rate Code")]
    public int RateCode { get; set; }

    [Required]
    [Display(Name = "Unit")]
    public string Unit { get; set; }

    [Required]
    [Display(Name = "Description")]
    public string Description { get; set; }

    [Required]
    [Display(Name = "Amount")]
    public decimal Amount { get; set; }

    public virtual ICollection<ProjectMaterial> ProjectMaterials { get; set; }
}

Code from project controller class...

public class ProjectMaterialController : Controller
{
    private ContructorContext db = new ContructorContext();

    //
    // GET: /ProjectMaterial/

    public ViewResult Index()
    {
        var projectmaterials = db.ProjectMaterials.Include(p => p.Scopes).Include(p => p.Rates);

        return View(projectmaterials.ToList());
    }



    //
    // GET: /ProjectMaterial/Details/5

    public ViewResult Details(int id)
    {
        ProjectMaterial projectmaterial = db.ProjectMaterials.Find(id);
        return View(projectmaterial);
    }

    //
    // GET: /ProjectMaterial/Create

    public ActionResult Create()
    {
        ViewBag.ScopeID = new SelectList(db.Scopes, "ScopeID", "ScopeName");
        ViewBag.RateID = new SelectList(db.Rates, "RateID", "Unit");
        return View();
    } 

    //
    // POST: /ProjectMaterial/Create

    [HttpPost]
    public ActionResult Create(ProjectMaterial projectmaterial)
    {
        if (ModelState.IsValid)
        {
            db.ProjectMaterials.Add(projectmaterial);
            db.SaveChanges();
            return RedirectToAction("Index");  
        }

        ViewBag.ScopeID = new SelectList(db.Scopes, "ScopeID", "ScopeName", projectmaterial.ScopeID);
        ViewBag.RateID = new SelectList(db.Rates, "RateID", "Unit", projectmaterial.RateID);
        return View(projectmaterial);
    }

    //
    // GET: /ProjectMaterial/Edit/5

    public ActionResult Edit(int id)
    {
        ProjectMaterial projectmaterial = db.ProjectMaterials.Find(id);
        ViewBag.ScopeID = new SelectList(db.Scopes, "ScopeID", "ScopeName", projectmaterial.ScopeID);
        ViewBag.RateID = new SelectList(db.Rates, "RateID", "Unit", projectmaterial.RateID);
        return View(projectmaterial);
    }

    //
    // POST: /ProjectMaterial/Edit/5

    [HttpPost]
    public ActionResult Edit(ProjectMaterial projectmaterial)
    {
        if (ModelState.IsValid)
        {
            db.Entry(projectmaterial).State = EntityState.Modified;
            db.SaveChanges();
            return RedirectToAction("Index");
        }
        ViewBag.ScopeID = new SelectList(db.Scopes, "ScopeID", "ScopeName", projectmaterial.ScopeID);
        ViewBag.RateID = new SelectList(db.Rates, "RateID", "Unit", projectmaterial.RateID);
        return View(projectmaterial);
    }

    //
    // GET: /ProjectMaterial/Delete/5

    public ActionResult Delete(int id)
    {
        ProjectMaterial projectmaterial = db.ProjectMaterials.Find(id);
        return View(projectmaterial);
    }

    //
    // POST: /ProjectMaterial/Delete/5

    [HttpPost, ActionName("Delete")]
    public ActionResult DeleteConfirmed(int id)
    {            
        ProjectMaterial projectmaterial = db.ProjectMaterials.Find(id);
        db.ProjectMaterials.Remove(projectmaterial);
        db.SaveChanges();
        return RedirectToAction("Index");
    }

Thanx in advance guys!! really need your help.

It's unclear what you are trying to do. Are you trying to calculate the totals in the controller and pass it back to a view OR are you trying to calculate a total in a controller and have it available to ALL other views? — Sean, Jan 19 '12 at 09:06
Thanx, I want to calculate and pass the result to all the other views (Index, details & Delete) except the edit view because the total will be a calculated value.. — Thuto Paul Gaotingwe, Jan 19 '12 at 09:42

score 9 · Accepted Answer · edited May 23 '17 at 11:53

Seeing as you say you're new to MVC, I've given you a few options and explained which is best and why, because it's better to understand now so you don't get in to bad habits, especially if you start building larger projects.

You don't necessarily need to create a variable, because you can do that calculation in your view. Because you are passing the domain model directly to the view you can do (in razor):

@(Model.Quantity * Model.Rates.Amount)

Although this is the easiest option I wouldn't necessarily recommend this as views should be dumb - see ASP.NET MVC: How dumb should my view be?.

Another option is to do the calculation in the controller and pass the value in the ViewBag, e.g.:

public ViewResult Details(int id)
{
    ProjectMaterial projectmaterial = db.ProjectMaterials.Find(id);
    ViewBag.Price = projectmaterial.Quantity * projectmaterial.Rates.Amountl
    return View(projectmaterial);
}

Then you could use it in your view like:

@ViewBag.Price

Again, this is easy but I wouldn't recommend it, as ViewBag isn't strongly typed - see Is using ViewBag in MVC bad?.

You could put a property on your ProjectMaterial class like, which is a neat solution.

public decimal Price
{
    get
    {
        return Quantity * Rates.Amount;
    }
}

However, if Price is a property that is only ever used within your views (ie you just display it) then it probably shouldn't be in your domain model, as your domain model is just that - storing and accessing the raw data.

Maybe the best way is to create a viewmodel specific to your view (see http://stephenwalther.com/blog/archive/2009/04/13/asp.net-mvc-tip-50-ndash-create-view-models.aspx) with a Price propert. This means that the property is only used where it is needed, the domain model remains just that, your view remains dumb and your domain model is not exposed to your view. See Why Two Classes, View Model and Domain Model? also for a good explanation of view models

Thanks a lot!!! i wanted the best way of doing it and am reading through your links now, i tried the one where I put a property in the ProjectMaterial Class before (yesterday) and it did not work well for me, every-time i create a new project material i will get a Null-Reference Exception, because Rates.Amount was **NULL** i realized this was a logical error because i knew it was not true because the rates table was populated. Again Thanx a lot!! — Thuto Paul Gaotingwe, Jan 19 '12 at 10:17

score 2 · Answer 2 · answered Jan 19 '12 at 09:05

2

You could add a property to your ProjectMaterial model:

public decimal Price
{
    get
    {
        return Quantity * Rates.Amount;
    }
}

answered Jan 19 '12 at 09:05

Darin Dimitrov

1,023,142
271
3,287
2,928

I tried this earlier and it looked like it was going to work because all the Project Material views appeared to be fine **but every time** i create a **new ProjectMaterial** i received a Null-reference exception error. it complained that Rates.Amount was null which was not true because i populated the rates table – Thuto Paul Gaotingwe Jan 19 '12 at 09:51

score 1 · Answer 3 · edited Nov 25 '18 at 12:44

1

@(int.Parse(variable) * your value)

edited Nov 25 '18 at 12:44

Zoe

27,060
21
118
148

answered Nov 25 '18 at 12:29

Raviteja V

454
5
11

when we need multiply the string values in razor view we can use like this. – Raviteja V Dec 09 '18 at 07:10

score 0 · Answer 4 · answered Mar 25 '20 at 15:47

Additional to all the answers you can use Data Format String in model class, and Html Helper in View to maintain formatting in displayed results for numeric types, by modifying returned attribute in the Controller.

The purpose of applying the formatting in the model class, and the value transformation in the controller and keeping the view standard, is to achieve separation of concerns (SoC) for easier maintenance, and control over the code.

Consider this example:

Products Class Property

[Display(Name = "Max Disc %")]
[DisplayFormat(DataFormatString = "{0:P1}", ApplyFormatInEditMode = true)]
public decimal MaxDiscountRate { get; set; }

Products Controller

        [HttpGet]
        public ActionResult Details(int id)
        {
            if (id == 0)
            {
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
            }
            Products products = _uow.Products.GetById(id);
            if (products == null)
            {
                return HttpNotFound();
            }
            else
            {
                products.MaxDiscountRate /= 100;
            }

            return View(products);
        }

Products Details View

<div class="detail">
   <h5 class="text-teal">@Html.DisplayNameFor(model => model.MaxDiscountRate)</h5>
   <span class="text-peru">@Html.DisplayFor(model => model.MaxDiscountRate)</span>
</div>

score 0 · Answer 5 · answered Jan 19 '12 at 09:23

You might want to have a model function with instances of your self.rate, and self.material items passed on from your views. Or otherwise you can individually calculate the values of the multiplication in each view.

Either way, you should be able to store the copy over the value of multiplication (variable1) in the view's bag, and pass it onto each view without having to save it in the DB.

ViewBag.variable1 = rate*material
return View()

How to make simple calculations using model items and an input from a form in ASP.net MVC 3?

5 Answers5