求解 MVC5 ASP.NET 二次方程

Question

我正在尝试构建我的第一个 ASP.NET MVC 应用程序来解决二次方程，但我在向视图显示结果时遇到问题。 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);
}
}
}
}

控制器

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);
}
}
}

视图

@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")
}

我确实无法将结果显示到视图

Answer 1

这里有几个问题。

首先，你从不首先调用Calculate函数。因此，您的Solve模型从未得到x1和x2计算。

其次，由于您将两个参数x1和x2作为Calculate函数的输入，因此它们"屏蔽"了Solve模型字段x1和x2- 用于在视图中显示结果。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( 来指示它是剃刀语法。

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);
}
}

控制器

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);
}
}         
}

视图

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