ASP.NET 二次计算错误地返回 NaN

Question

我的 ASP.NET MVC Web 应用程序应该计算二次多项式（二次）的根，但我错误地得到了 Nan 响应。我相信这是由于我的设置不当造成的，所以让我在这里发布一些代码：

视图：

<%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<RootFinder.Models.QuadCalc>" %>

<asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server">
Polynomial Root Finder - Quadratic
</asp:Content>

<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">
    <h2>Quadratic</h2>

    <% using(Html.BeginForm("Quadratic", "Calculate")) %>
    <% { %>
    <div>
        a: <%= Html.TextBox("quadAValue", Model.quadraticAValue) %>
        <br />
        b: <%= Html.TextBox("quadBValue", Model.quadraticBValue) %>
        <br />
        c: <%= Html.TextBox("quadCValue", Model.quadraticCValue) %>
        <br />
        <input type="submit" id="quadraticSubmitButton" value="Calculate!" />
        <br />
        <br />
        <strong>Root 1:</strong>
        <p><%= Model.x1 %></p>
        <br />
        <strong>Root 2:</strong>
        <p><%= Model.x2 %></p>
    </div>
    <% } %>
</asp:Content>

控制器（处理二次计算等计算请求的所有控制）：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using RootFinder.Models;

namespace RootFinder.Controllers
{
    public class CalculateController : Controller
    {
        //
        // GET: /Calculate/

        public ActionResult Index()
        {
            return View();
        }

        [HttpGet]
        public ViewResult Quadratic()
        {
            return View(new QuadCalc());
        }

        [HttpPost]
        public ViewResult Quadratic(QuadCalc newQuadCalc)
        {
            newQuadCalc.QuadCalculate();
            return View(newQuadCalc);
        }

        public ActionResult Cubic()
        {
            return View();
        }

        public ActionResult Quartic()
        {
            return View();
        }
    }
}

模型（执行计算）：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace RootFinder.Models
{
    public class QuadCalc
    {
        public double quadraticAValue { get; set; }
        public double quadraticBValue { get; set; }
        public double quadraticCValue { get; set; }
        public double x1 { get; set; }
        public double x2 { get; set; }

        public void QuadCalculate()
        {
            //Quadratic Formula: x = (-b +- sqrt(b^2 - 4ac)) / 2a

            //Calculate discriminant
            double insideSquareRoot = (quadraticBValue * quadraticBValue) - 4 * quadraticAValue * quadraticCValue;

            if (insideSquareRoot < 0)
            {
                //No real solution
                x1 = double.NaN;
                x2 = double.NaN;
            }
            else if (insideSquareRoot == 0)
            {
                //One Solution
                double sqrtOneSolution = Math.Sqrt(insideSquareRoot);
                x1 = (-quadraticBValue + sqrtOneSolution) / (2 * quadraticAValue);
                x2 = double.NaN;
            }
            else if (insideSquareRoot > 0)
            {
                //Two Solutions
                double sqrtTwoSolutions = Math.Sqrt(insideSquareRoot);
                x1 = (-quadraticBValue + sqrtTwoSolutions) / (2 * quadraticAValue);
                x2 = (-quadraticBValue - sqrtTwoSolutions) / (2 * quadraticAValue);
            }
        }
    }
}

所以，让我们在视图中说，最终用户输入 a=1、b=0 和 c=0，我的应用程序将输出 Nan对于 Root1 和 Root2。我认为这可能是由于我没有将最终用户输入正确连接到 newQuadCalc 对象的实例变量中......

Answer 1

您的代码失败，因为在网站上输入的值不会传播到您的计算逻辑。发生这种情况是因为文本框名称与模型属性名称不匹配导致模型绑定失败。你的观点应该是这样的：

<% using (Html.BeginForm("Quadratic", "Calculate")) %>
<% { %>
<div>
    a: <%= Html.TextBoxFor(m=> m.quadraticAValue) %>
    <br />
    b: <%= Html.TextBoxFor(m => m.quadraticBValue) %>
    <br />
    c: <%= Html.TextBoxFor(m => m.quadraticCValue)%>
    <br />
    <input type="submit" id="quadraticSubmitButton" value="Calculate!" />
    <br />
    <strong>Root 1:</strong>
    <p><%= Html.DisplayFor(m => m.x1) %></p>
    <br />
    <strong>Root 2:</strong>
    <p><%= Html.DisplayFor(m => m.x2)%></p>
</div>
<% } %>