I am getting this error message with the following code "RuntimeBinderException: Cannot perform runtime binding on a null reference" and can't solve

matt mosinski 0
Viewed 13

This is the Model that I have:

namespace MattsSportsEmporium.Models
{
    public class PriceCalculator
    {
        public decimal Subtotal { get; set; }
        public decimal TaxPercent { get; set; }
        public decimal TaxAmount { get; set; }
        public decimal Total { get; set; }
        public decimal CalculatePrice()
        {

            decimal Total = (Subtotal * (TaxAmount / 100)) + Subtotal;

            return Total;
        }

        public decimal CalculateTax()
        {

            decimal TaxAmount = Subtotal * (TaxPercent / 100);

            return TaxAmount;
        }

    }
}

This is the Controller:

using Microsoft.AspNetCore.Mvc;
using MattsSportsEmporium.Models;


namespace MattsSportsEmporium.Controllers
{
    public class HomeController : Controller
    {
        [HttpGet]
        public IActionResult Index(decimal Total)
        {

            ViewBag.CP = 0;
            return View();
        }
        [HttpPost]
        public IActionResult Index(PriceCalculator model)
        {
            ViewBag.CP = model.CalculatePrice();
            return View(model);
        }

        [HttpGet]
        public IActionResult Index1(decimal TaxAmount)
        {

            ViewBag.CT = 0;
            return View();
        }
        [HttpPost]
        public IActionResult Index1(PriceCalculator model)
        {
            ViewBag.CT = model.CalculateTax();
            return View(model);
        }
    }
}

This is the View:

@using MattsSportsEmporium.Models
@model PriceCalculator
@{
    Layout = null;
}
<!DOCTYPE html>
<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Matt's Sports Emporium</title>
    <style>
        /* all of the CSS styles from figure 2-14 go here */
        body {
            padding: 1em;
            font-family: Arial, Arial, Helvetica, sans-serif;
        }

        h1 {
            margin-top: 0;
            color: navy;
        }

        label {
            display: inline-block;
            width: 10em;
            padding-right: 1em;
        }

        div {
            margin-bottom: .5em;
        }
    </style>
</head>
<body>
    <h1>Matt's Sports Emporium</h1>
    <form asp-action="Index" method="post">
        <div>
            <label asp-for="Subtotal">
                Subtotal:
            </label>
            <input asp-for="Subtotal" />
        </div>
        <div>
            <label asp-for="TaxPercent">
                Tax Percent:
            </label>
            <input asp-for="TaxPercent" />
        </div>
        <div>
            <label>TaxAmount: </label>
            <input value="@ViewBag.CT.ToString("C2")" readonly />

        </div>
        <div>
            <label>Total: </label>
            <input value="@ViewBag.CP.ToString("C2")" readonly />
        </div>
        <button type="submit">Calculate</button>
        <a asp-action="Index">Clear</a>
    </form>
</body>
</html>

The app should display an input box where the user enters a subtotal followed by an input box where the user enters a tax percentage. The next line displays the tax based on the first two user entries. The last line displays the total with tax.

asp.net-mvc
1 Answers

The idea of achieving the above function is incorrect base on your solution.

This for your model is sufficient

 public class PriceCalculator
    {
        public decimal Subtotal { get; set; }
        public decimal TaxPercent { get; set; }
        public decimal TaxAmount { get; set; }
        public decimal Total { get; set; }

        public void CalculateTotal()
        {
            decimal _TaxAmount = Math.Round(SubTotal * TaxPercent / 100,2);
            decimal _Total = SubTotal + _TaxAmount;
            
            TaxAmount = _TaxAmount;
            Total = _Total;

        }
    }

On your controller. That is sufficient

 public IActionResult Index()
        {
            PriceCalculator model = new PriceCalculator();

            model.TaxPercent = 6; // pass your tax value here

            return View(model);
        }
      
       [HttpPost]
       public IActionResult Index(decimal SubTotal, decimal TaxPercent)
        {
           ModelState.Clear();

            PriceCalculator model = new PriceCalculator();

           model.SubTotal = SubTotal;
           model.TaxPercent = TaxPercent;

           model.CalculateTotal(); //calcualte here

            return View(model); // then return back the model
        }

In your view

<body>
    <h1>Matt's Sports Emporium</h1>
    <form asp-action="Index" method="post">
        <div>
            <label asp-for="Subtotal">
                Subtotal:
            </label>
            <input asp-for="Subtotal" onChange= "CalculateTotal()" />
        </div>
        <div>
            <label asp-for="TaxPercent">
                Tax Percent:
            </label>
            <input asp-for="TaxPercent"/>
        </div>
        <div>
            <label>TaxAmount: </label>
            <input asp-for="TaxAmount" ReadOnly = True"/>

        </div>
        <div>
            <label asp-for="Total">
               Total:
            </label>
            <input asp-for="Total"/>
        </div>
        <button type="submit">Calculate</button>
        <a asp-action="Index">Clear</a>
    </form>
</body>

This is one of the way to achieve what u try to do. However, this solution is rather weak. You should use javascript in the view to do the calculation instead of post back to calculate the total.

Yat Fei Leong0
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