c# - 异常 "There is no ViewData item of type ' IEnumerable"MVC

Question

大家好，我是 MVC 的新手，我找不到以下异常的解决方案。

“不存在具有键‘部门’的‘IEnumerable’类型的 ViewData 项。”

这是它的cshtml代码

@using LearningMVCDAL
@using LearningMVCDAL.Classes
@model Employee

@{
    ViewBag.Title = "Create";
}

<h2>Create</h2>

@using (Html.BeginForm())
{
    @Html.ValidationSummary(true)

    <fieldset>
        <legend>Employee</legend>

        <div class="editor-label">
            @Html.LabelFor(model => model.Name)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.Name)
            @Html.ValidationMessageFor(model => model.Name)
        </div>

        <div class="editor-label">
            @Html.LabelFor(model => model.Gender)
        </div>
        <div class="editor-field">
            @Html.DropDownList("Gender", new List<SelectListItem>{ 
       new SelectListItem { Text="Male", Value="Male"},
       new SelectListItem { Text="Female", Value="Female"}},"Select Gender")
            @Html.ValidationMessageFor(model => model.Gender)
        </div>

        <div class="editor-label">
            @Html.LabelFor(model => model.City)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.City)
            @Html.ValidationMessageFor(model => model.City)
        </div>
        <div class="editor-label">
            @Html.Label("Department")
        </div>
        <div class="editor-field">
            @Html.DropDownList("Department", (IEnumerable<SelectListItem>)ViewBag.Departments,"Select Department")
        </div>
        <p>
            <input type="submit" value="Create" />
        </p>
    </fieldset>
}

<div>
    @Html.ActionLink("Back to List", "Index")
</div>

Controller 代码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using LearningMVCBLL;
using LearningMVCDAL;
using LearningMVCDAL.Classes;

namespace LearningMVC.Controllers
{
    public class EmployeeController : Controller
    {

        #region ObjectDeclartions
        EmployeeBusinessLayer objEmployeeBusinessLayer = new EmployeeBusinessLayer();
        DepartmentBusinessLayer objDepartmentBusinessLayer = new DepartmentBusinessLayer();
        #endregion
        public ActionResult Index()
        {
            List<Employee> employees = objEmployeeBusinessLayer.Employee;
            return View(employees);
        }
        [HttpGet]
        public ActionResult Create()
        {
            List<Department> departments = new List<Department>();
            departments = objDepartmentBusinessLayer.Department;
            SelectList departmentList = new SelectList(departments, "ID", "Name");
            ViewBag.Departments = departmentList;
            return View();
        }
        [HttpPost]
        public ActionResult Create(FormCollection formCollection)
        {
            if (ModelState.IsValid)
            {
                foreach (string key in formCollection.AllKeys)
                {
                    Response.Write("Key = " + key + "  ");
                    Response.Write("Value = " + formCollection[key]);
                    Response.Write("<br/>");
                }
            }
            return View();
        }
    }
}

我更改了它，但仍然出现相同的错误。当我发布数据时出现此错误“HttpPost”创建函数被调用。提前致谢。

Answer 1

尝试在使用 Post HttpMethod 的创建操作中添加 ViewBag.Departments，如下所示:

[HttpPost]
        public ActionResult Create(FormCollection formCollection)
        {
            if (ModelState.IsValid)
            {
                foreach (string key in formCollection.AllKeys)
                {
                    Response.Write("Key = " + key + "  ");
                    Response.Write("Value = " + formCollection[key]);
                    Response.Write("<br/>");
                }
            }
        List<Department> departments = new List<Department>();
        departments = objDepartmentBusinessLayer.Department;
        SelectList departmentList = new SelectList(departments, "ID", "Name");
        ViewBag.Departments = departmentList;
            return View();
        }