c# - 在 ASP.NET MVC5 中求解二次方程

Question

我正在尝试构建我的第一个求解二次方程的 ASP.NET MVC 应用程序，但我在将结果显示到 View 时遇到问题。这是我的模型

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

namespace Resolve.Models
{
public class Solve
{
    public double a { get; set; }
    public double b { get; set; }
    public double c { get; set; }
    public double x1 { get; set; }
    public double x2 { get; set; }

   public void Calculate (out double x1, out double x2)
    {
        double inside = (b * b) - 4 * a * c;

        if (inside < 0)
        {
            x1 = double.NaN;
            x2 = double.NaN;
        }
        else
        {
            double eqn = Math.Sqrt(inside);
            x1 = (-b + eqn) / (2 * a);
            x2 = (-b - eqn) / (2 * a);
        }
    }
}
}

Controller

namespace Resolve.Controllers
{
public class EquationController : Controller
{
 // GET: Equation
    public ActionResult Promise()
    {
        return View();
    }
    [AcceptVerbs(HttpVerbs.Post)]
    public ActionResult Promise(Solve equation)
    {

        return View(equation);
    }
 }
 }

查看

  @model Resolve.Models.Solve

 @{
 ViewBag.Title = "Promise";
 }

<h2>Promise</h2>


@using (Html.BeginForm()) 
{
@Html.AntiForgeryToken()

<div class="form-horizontal">
    <h4>Solve</h4>
    <hr />

    @Html.ValidationSummary(true, "", new { @class = "text-danger" })
    <div class="form-group">
        @Html.LabelFor(model => model.a, htmlAttributes: new { @class = 
 "control-label col-md-2" })
        <div class="col-md-10">
            @Html.EditorFor(model => model.a, new { htmlAttributes = new { 
 @class = "form-control" } })
            @Html.ValidationMessageFor(model => model.a, "", new { @class = 
"text-danger" })
        </div>
    </div>

    <div class="form-group">
        @Html.LabelFor(model => model.b, htmlAttributes: new { @class = 
"control-label col-md-2" })
        <div class="col-md-10">
            @Html.EditorFor(model => model.b, new { htmlAttributes = new { 
@class = "form-control" } })
            @Html.ValidationMessageFor(model => model.b, "", new { @class = 
"text-danger" })
        </div>
    </div>

    <div class="form-group">
        @Html.LabelFor(model => model.c, htmlAttributes: new { @class = 
"control-label col-md-2" })
        <div class="col-md-10">
            @Html.EditorFor(model => model.c, new { htmlAttributes = new { 
 @class = "form-control" } })
            @Html.ValidationMessageFor(model => model.c, "", new { @class = 
"text-danger" })
        </div>
    </div>

    <p>Model.x1 : </p> <p>Model.x2</p>



    <div class="form-group">
        <div class="col-md-offset-2 col-md-10">
            <input type="submit" value="Solve" class="btn btn-default" />
        </div>
    </div>
  </div>
}



@section Scripts {
@Scripts.Render("~/bundles/jqueryval")
}

我在向 View 显示结果时遇到了问题

Answer 1

这里有几个问题。

首先，您从一开始就不会调用Calculate 函数。因此，您的 Solve 模型从未计算过它们的 x1 和 x2。

其次，由于您将两个参数 x1 和 x2 作为 Calculate 函数的输入，它们“屏蔽”了 Solve 模型字段 x1 和 x2 - 用于在 View 中显示结果。你也应该把它们拿出来。

第三，正如您所发现的，Model.x1 和 Model.x2 的语法应该使用 @ 作为前缀(即 @Model.x1) 表明它是一个 Razor 语法。

这是你应该做的:

模型方法

public void Calculate () //removes the out double for x1 and x2
{
    double inside = (b * b) - 4 * a * c;

    if (inside < 0)
    {
        x1 = double.NaN;
        x2 = double.NaN;
    }
    else
    {
        double eqn = Math.Sqrt(inside);
        x1 = (-b + eqn) / (2 * a);
        x2 = (-b - eqn) / (2 * a);
    }
}

Controller

namespace Resolve.Controllers
{

    public class EquationController : Controller
    {
     // GET: Equation
        public ActionResult Promise()
        {
            return View();
        }

        //[AcceptVerbs(HttpVerbs.Post)] //don't use this
        [HttpPost] //use this instead
        public ActionResult Promise(Solve equation)
        {
            equation.Calculate(); //calls this
            return View(equation);
        }
     }         

 }

查看

<p>@Model.x1 : </p> <p>@Model.x2</p>