MVC 4 根据 DropDownListFor 选择更改多个显示字段

Question

MVC 4 Changing a field based on DropDownListFor selection

首先，与上述问题几乎相同，但解决方案不适用于这个问题。

我有一个包含下拉列表的页面。选择后，它将根据选择更改显示字段。

视图中的javascript是：

<script type="text/javascript">
    $(function(){
        $('#courseName').on('change', function () {
            var courseID = $(this).val();
            var studentID = '@ViewBag.StudentID';
            $.ajax({
                url: '@Url.Action("FillCourseInfo", "Student")',
                data: {StudentID: studentID, CourseID: courseID},
                type: 'get'
            }).done(function(data){
                $('#courseStartDate').text(data.courseStartDate); 
                $('#courseEndDate').text(data.courseEndDate);
                $('#projectName').text(data.projectName);
                $('#graduated').text(data.graduated);
            });
        });
    });

</script>

观点：

<tr>
            <th class="table-row">
                Course Title:
            </th>
            <td class="table-row">
                @Html.DropDownListFor(m => m.courseName,
                    @ViewBag.courseList as SelectList, " -- Select Course -- ",
                    new { @class = "form-control" })
            </td>
        </tr>
        <tr>
            <th class="table-row">
                Start & End Date:
            </th>
            <td class="table-row">
                <label id="#courseStartDate" class="form-control">@Model.courseStartDate</label>
            </td>
            <td class="table-row">
                <label id="#courseEndDate" class="form-control">@Model.courseEndDate</label>
            </td>
        </tr>
        <tr>
            <th class="table-row">
                Project:
            </th>
            <td class="table-row">
                <label id="#projectName" class="form-control">@Model.projectName</label>
            </td>
        </tr>
        <tr>
            <th class="table-row">
                Graduated:
            </th>
            <td class="table-row">
                <label id="#graduated">@Model.graduated</label>
            </td>
        </tr>

以及Controller方法：

[HttpGet]
        public JsonResult FillCourseInfo(int StudentID, int CourseID)
        {
            var ret = (from e in db.Enrollments 
                       join c in db.Courses on e.CourseID equals c.CourseID
                       where e.StudentID == StudentID && e.CourseID == CourseID
                       select new
                       {
                           courseStartDate = c.CourseStartDate,
                           courseEndDate = c.CourseEndDate,
                           projectName = e.Project.ProjectTitle,
                           graduated = e.Graduated

                       }).ToList()
                       .Select(a => new StudentCourseDetails() {
                           courseStartDate = a.courseStartDate.ToString("MMM d, yyyy"),
                           courseEndDate = a.courseEndDate.ToString("MMM d, yyyy"),
                           projectName = a.projectName,
                           graduated = a.graduated.Value.ToString()
                       }).FirstOrDefault();
            string sd = ret.courseStartDate;
            string ed = ret.courseEndDate;
            string pn = ret.projectName;
            string g = ret.graduated;
            return Json(ret, JsonRequestBehavior.AllowGet);
        }

目前 javascript 没有被命中，或者我的方法没有被调用。

Answer 1

您正在做的一件事是没有从您的 FillCourseInfo 操作返回单个结果。

这意味着您的 json 结果是StudentCourseDetails 的列表。您必须使用 $('#Dates').val(data[0].courseDates); 来获取您的值。

或者，如果您只期望一个值，您可以在 linq 查询结束时使用 .FirstOrDefault()。

var ret = (from e in db.Enrollments 
               join c in db.Courses on e.CourseID equals c.CourseID
               where e.StudentID == StudentID && e.CourseID == CourseID
               select new StudentCourseDetails
               {
                   courseDates = c.CourseStartDate.ToString() + " " + c.CourseEndDate.ToString(),
                   projectName = e.Project.ProjectTitle,
                   graduated = e.Graduated

               }).FirstOrDefault();

我为您创建了另一个 .NET Fiddle。 DotNetFiddle

要在您的 linq 查询中使用 ToString，请将结果转换为列表，然后构建您的 json

 var ret = (from e in db.Enrollments
                   join c in db.Courses on e.CourseID equals c.CourseID
                   where e.StudentID == StudentID && e.CourseID == CourseID
                   select new
                   {
                       courseStartDate = c.CourseStartDate,
                       courseEndDate = c.CourseEndDate,
                       projectName = e.Project.ProjectTitle,
                       graduated = e.Graduated

                   }).ToList()
                   .Select(a => new StudentCourseDetails() {
                       courseDates = a.courseStartDate.ToString() + " " + a.courseEndDate.ToString(),
                       projectName = a.projectName,
                       graduated = a.graduated
                   }).FirstOrDefault();

Answer 2

使用以下函数更改您的 Javascript 函数：

$("#CourseName").change(function () {

            var courseID = $(this).val();
            $.ajax({
                type: 'POST',
                url: '@Url.Action("FillCourseInfo","Student")', // we are calling json method
                dataType: 'json',
                data: { StudentID: @ViewBag.studentID, CourseID, courseID  },


                success: function (ret) {
            $('#Dates').val(ret.courseDates); 
                    $('#Project').val(ret.projectName);
                    $('#Graduated').val(ret.graduated);

                },
                error: function (ex) {
                    //alert('Failed to retrieve states.' + ex);
                }
            });

            return false;
        });

使用以下功能更改您的控制器功能

public JsonResult FillCourseInfo(int StudentID, int CourseID)
{
     var ret = (from e in db.Enrollments 
               join c in db.Courses on e.CourseID equals c.CourseID
               where e.StudentID == StudentID && e.CourseID == CourseID
               select new StudentCourseDetails
               {
                   courseDates = c.CourseStartDate.ToString() + " " + c.CourseEndDate.ToString(),
                   projectName = e.Project.ProjectTitle,
                   graduated = e.Graduated

               });
    return Json(ret);
}