我是MVC的新手(数据库优先),我有一个问题 我有一个带有DropDownList控件的窗体。 DropDownList控件已绑定到数据库上的一列,但我希望将默认值作为项目的一部分,例如“ --select grade--” 我该怎么办? 我有几个从脚手架生成的视图和控制器。
我将附加我的视图以及该特定对象的控制器。 DropDownLists @ Html.DropDownList(“ StudentID”,null,htmlAttributes:new {@class =“ form-control”})
和
@ Html.DropDownList(“ CourseID”,null,htmlAttributes:新的{@class =“ form-control”})
是关注点
@model ContosoSite.Models.Enrollment
@{
ViewBag.Title = "Create";
}
<h2>Create</h2>
@using (Html.BeginForm())
{
@Html.AntiForgeryToken()
<div class="form-horizontal">
<h4>Enrollment</h4>
<hr />
@Html.ValidationSummary(true, "", new { @class = "text-danger" })
<div class="form-group">
@Html.LabelFor(model => model.Grade, htmlAttributes: new { @class = "control-label col-md-2" })
<div class="col-md-10">
@Html.EditorFor(model => model.Grade, new { htmlAttributes = new { @class = "form-control" } })
@Html.ValidationMessageFor(model => model.Grade, "", new { @class = "text-danger" })
</div>
</div>
<div class="form-group">
@Html.LabelFor(model => model.CourseID, "CourseID", htmlAttributes: new { @class = "control-label col-md-2" })
<div class="col-md-10">
@Html.DropDownList("CourseID", null, htmlAttributes: new { @class = "form-control" })
@Html.ValidationMessageFor(model => model.CourseID, "", new { @class = "text-danger" })
</div>
</div>
<div class="form-group">
@Html.LabelFor(model => model.StudentID, "StudentID", htmlAttributes: new { @class = "control-label col-md-2" })
<div class="col-md-10">
@Html.DropDownList("StudentID", null, htmlAttributes: new { @class = "form-control" })
@Html.ValidationMessageFor(model => model.StudentID, "", new { @class = "text-danger" })
</div>
</div>
<div class="form-group">
<div class="col-md-offset-2 col-md-10">
<input type="submit" value="Create" class="btn btn-default" />
</div>
</div>
</div>
}
<div>
@Html.ActionLink("Back to List", "Index")
</div>
@section Scripts {
@Scripts.Render("~/bundles/jqueryval")
}
using System;
using System.Collections.Generic;
using System.Data;
using System.Data.Entity;
using System.Linq;
using System.Net;
using System.Web;
using System.Web.Mvc;
using ContosoSite.Models;
namespace ContosoSite.Controllers
{
public class EnrollmentsController : Controller
{
private ContosoUniversityEntities db = new ContosoUniversityEntities();
// GET: Enrollments
public ActionResult Index()
{
var enrollments = db.Enrollments.Include(e => e.Course).Include(e => e.Student);
return View(enrollments.ToList());
}
// GET: Enrollments/Details/5
public ActionResult Details(int? id)
{
if (id == null)
{
return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
}
Enrollment enrollment = db.Enrollments.Find(id);
if (enrollment == null)
{
return HttpNotFound();
}
return View(enrollment);
}
// GET: Enrollments/Create
public ActionResult Create()
{
ViewBag.CourseID = new SelectList(db.Courses, "CourseID", "Title");
ViewBag.StudentID = new SelectList(db.Students, "StudentID", "LastName");
return View();
}
// POST: Enrollments/Create
// To protect from overposting attacks, please enable the specific properties you want to bind to, for
// more details see https://go.microsoft.com/fwlink/?LinkId=317598.
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Create([Bind(Include = "EnrollmentID,Grade,CourseID,StudentID")] Enrollment enrollment)
{
if (ModelState.IsValid)
{
db.Enrollments.Add(enrollment);
db.SaveChanges();
return RedirectToAction("Index");
}
ViewBag.CourseID = new SelectList(db.Courses, "CourseID", "Title", enrollment.CourseID);
ViewBag.StudentID = new SelectList(db.Students, "StudentID", "LastName", enrollment.StudentID);
return View(enrollment);
}
// GET: Enrollments/Edit/5
public ActionResult Edit(int? id)
{
if (id == null)
{
return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
}
Enrollment enrollment = db.Enrollments.Find(id);
if (enrollment == null)
{
return HttpNotFound();
}
ViewBag.CourseID = new SelectList(db.Courses, "CourseID", "Title", enrollment.CourseID);
ViewBag.StudentID = new SelectList(db.Students, "StudentID", "LastName", enrollment.StudentID);
return View(enrollment);
}
// POST: Enrollments/Edit/5
// To protect from overposting attacks, please enable the specific properties you want to bind to, for
// more details see https://go.microsoft.com/fwlink/?LinkId=317598.
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Edit([Bind(Include = "EnrollmentID,Grade,CourseID,StudentID")] Enrollment enrollment)
{
if (ModelState.IsValid)
{
db.Entry(enrollment).State = EntityState.Modified;
db.SaveChanges();
return RedirectToAction("Index");
}
ViewBag.CourseID = new SelectList(db.Courses, "CourseID", "Title", enrollment.CourseID);
ViewBag.StudentID = new SelectList(db.Students, "StudentID", "LastName", enrollment.StudentID);
return View(enrollment);
}
// GET: Enrollments/Delete/5
public ActionResult Delete(int? id)
{
if (id == null)
{
return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
}
Enrollment enrollment = db.Enrollments.Find(id);
if (enrollment == null)
{
return HttpNotFound();
}
return View(enrollment);
}
// POST: Enrollments/Delete/5
[HttpPost, ActionName("Delete")]
[ValidateAntiForgeryToken]
public ActionResult DeleteConfirmed(int id)
{
Enrollment enrollment = db.Enrollments.Find(id);
db.Enrollments.Remove(enrollment);
db.SaveChanges();
return RedirectToAction("Index");
}
protected override void Dispose(bool disposing)
{
if (disposing)
{
db.Dispose();
}
base.Dispose(disposing);
}
}
}
答案 0 :(得分:0)
剃刀视图:
@Html.DropDownList("StudentGender",
new SelectList(Enum.GetValues(typeof(Gender))),
"Select Gender",
new { @class = "form-control" })
结果:
<select class="form-control" id="StudentGender" name="StudentGender">
<option>Select Gender</option>
<option>Male</option>
<option>Female</option>
</select>
参考http://www.tutorialsteacher.com/mvc/htmlhelper-dropdownlist-dropdownlistfor
答案 1 :(得分:0)
您可以使用DropDownList辅助方法的this overload。
public static DropDownList (thisHtmlHelper htmlHelper,
string name,
IEnumerable<System.Web.Mvc.SelectListItem> selectList,
string optionLabel,
IDictionary<string,object> htmlAttributes);
这里,第三个参数optionLabel
用于为默认项构建一个选项项。该选项将没有value
属性值。
因此,在您的情况下,您的查看代码将为
@Html.DropDownList("CourseID", ViewBag.CourseID as SelectList,
"--select grade--", new { @class = "form-control" })
这将呈现一个SELECT元素,其中第一个选项将是“ select grade”,并且将被选中(因为它是第一个)。如果您希望将其他选项项选为默认选项,请考虑对视图模型使用DropDownListFor
帮助方法。有关该方法的示例代码,请参见this post。