远程验证显示错误消息，但仍然允许表单提交并保存在数据库MVC 5中

Question

情况是， 学生注册的组合。 编号和选择课程始终是唯一的。

选择之前保存在数据库中的组合后，预期的结果是，

第一个预期成果：

将出现错误消息“已选择的学生已经学习此课程”。

第二个预期成果：

它将禁止表单提交，直到选择了之前未保存在数据库中的其他组合。

目前的结果：

第一预期结果运作良好：

但是，第二预期结果不起作用。 也就是说，它提交表单并保存之前保存在数据库中的组合。

能不能给出解决方案，因为我可以得到第二个预期的结果？

提前致谢。

为了便于阅读，我排除了与姓名，电子邮件和部门相关的所有代码，HTML和脚本。

这是我的模型，

using System;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Web.Mvc;

namespace UniversityApplication.Models
{
public class CourseStudent
{
    [Required]
    [DisplayName("Student Reg. No.")]
    public string CourseStudentRegNo { get; set; }

    [Required]
    [Remote("IsCourseNameExists", "CourseStudents", AdditionalFields = "CourseStudentRegNo", ErrorMessage = "Selected Student has taken this course already.")]
    [DisplayName("Select Course")]
    public string CourseStudentCourse { get; set; }

    [Required]
    [DisplayName("Date")]
    [DataType(DataType.Date)]
    public DateTime CourseStudentRegDate { get; set; }
}
}

这是我的控制器，

using System.Collections.Generic;
using System.Linq;
using System.Web.Mvc;
using UniversityApplication.Context;
using UniversityApplication.Models;

namespace UniversityApplication.Controllers
{
public class CourseStudentsController : Controller
{
    private ApplicationContext db = new ApplicationContext();

    public ActionResult StudentToCourse()
    {
        GenerateDropDownValue();
        return View();
    }


    [HttpPost]
    [ValidateAntiForgeryToken]
    public ActionResult StudentToCourse([Bind(Include = "CourseStudentID,CourseStudentRegNo,CourseStudentName,CourseStudentEmail,CourseStudentDepartmentCode,CourseStudentCourse,CourseStudentRegDate")] CourseStudent courseStudent)
    {
        GenerateDropDownValue();

        if (ModelState.IsValid)
        {
            db.CoursesStudents.Add(courseStudent);
            db.SaveChanges();
            ModelState.Clear();

            return View();
        }
        ModelState.Clear();

        return View();            
    }

private void GenerateDropDownValue()
    {
        List<Student> allRegisteredStudents = new List<Student>();
        List<SelectListItem> students = new List<SelectListItem>();

        List<Course> allCourses = new List<Course>();


        string studentName = "";
        string studentEmail = "";
        string studentDepartment = "";

        using (ApplicationContext db = new ApplicationContext())
        {
            allRegisteredStudents = db.Students.OrderBy(a => a.StudentRegNo).ToList();
        }

        foreach (var student in allRegisteredStudents)
        {
            students.Add(

                new SelectListItem()
                {
                    Value = student.StudentRegNo,
                    Text = student.StudentRegNo
                }
                );
        }

        ViewBag.Students = students;
        ViewBag.CourseCode = new SelectList(allCourses, "CourseCode", "CourseName");
        ViewBag.StudentName = studentName;
        ViewBag.StudentEmail = studentEmail;
        ViewBag.StudentDepartment = studentDepartment;
    }

    public JsonResult IsCourseNameExists(string CourseStudentCourse, string CourseStudentRegNo)
    {
        return Json(!db.CoursesStudents.Any(x => x.CourseStudentCourse == CourseStudentCourse && x.CourseStudentRegNo == CourseStudentRegNo), JsonRequestBehavior.AllowGet);
    }    

    protected override void Dispose(bool disposing)
    {
        if (disposing)
        {
            db.Dispose();
        }
        base.Dispose(disposing);
    }
}

}

这是我的观点，

@model UniversityApplication.Models.CourseStudent

@{
ViewBag.Title = "Create";
Layout = "~/Views/Shared/_Layout.cshtml";
}

<h2>Create</h2>


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

<div class="form-horizontal">
    <h4>CourseStudent</h4>
    <hr />
    @Html.ValidationSummary(true, "", new { @class = "text-danger" })
    <div class="form-group">
        @Html.LabelFor(model => model.CourseStudentRegNo, htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.DropDownListFor(model => model.CourseStudentRegNo, @ViewBag.Students as SelectList, "Select Student", new { @class = "form-control" })
            @Html.ValidationMessageFor(model => model.CourseStudentRegNo, "", new { @class = "text-danger" })
        </div>
    </div>        

    <div class="form-group">
        @Html.LabelFor(model => model.CourseStudentCourse, htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.DropDownListFor(model => model.CourseStudentCourse, @ViewBag.CourseCode as SelectList, "Select Course", new { @class = "form-control" })
            @Html.ValidationMessageFor(model => model.CourseStudentCourse, "", new { @class = "text-danger" })
        </div>
    </div>

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

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

<div>
@Html.ActionLink("Back to List", "Index")
</div>
<link href="~/Content/themes/base/all.css" rel="stylesheet" />
@section Scripts {

<script src="~/Scripts/jquery.validate.date.js"></script>
@Scripts.Render("~/bundles/jqueryui")
@Styles.Render("~/Content/cssjqryUi")
@Scripts.Render("~/bundles/jqueryval")

<script>

$(document).ready(function () {
    $('.date').datepicker({ dateFormat: "dd/mm/yy" });
});
</script>

}

Answer 1

不是通过JsonResult方法使用自定义远程验证IsCourseNameExists我建议通过自定义数据注释实现验证。

请参阅此链接，了解如何通过数据注释创建自定义验证： 自定义验证数据注释属性

如果验证不成功，则使用此方法，您将拥有无效的模型状态，您将不必担心错误。 它还使您的架构更安全。

此外，作为最佳实践，您应该在保存到数据库之前，在控制器的服务器端进行相同的检查（您正在使用IsCourseNameExists方法进行检查）。 注意：如果您只执行此检查，那么您的要求就会得到满足。

Answer 2

解决了

我错过了补充

<script src="~/Scripts/jquery-1.10.2.js"></script>
<script src="~/Scripts/jquery.validate.js"></script>
<script src="~/Scripts/jquery.validate.unobtrusive.js"></script>

在我的cshtml文件之上的脚本上面。

看起来像，

@model UniversityApplication.Models.CourseStudent

@{
ViewBag.Title = "Create";
Layout = "~/Views/Shared/_Layout.cshtml";
}

<h2>Create</h2>
<script src="~/Scripts/jquery-1.10.2.js"></script>
<script src="~/Scripts/jquery.validate.js"></script>
<script src="~/Scripts/jquery.validate.unobtrusive.js"></script>

//Rest codes