EntityFramework Core筆記(2)_CodeFirst配置_搭配MVC應用的開發

EntityFramework Core筆記(2)_CodeFirst配置_搭配MVC應用的開發_編輯、刪除

- 8月 30, 2021

編輯學生資訊

學生課程表資料若要進行編輯

流程會是

先從DB中根據ID來撈取該筆record然後反填到表單上呈現(GET部分)

user再去修改提交更新成新的資料(POST部分)

編輯的畫面基本上跟新增沒有太多差異

因此可以拿添加的檢視來複製貼上局部修改

Show.cshtml多增加操作的欄位表頭和跳轉到Edit 動作的連結

@{
    ViewData["Title"] = "顯示學生資訊";
}

<h3>@ViewData["Title"]</h3>

@model IEnumerable<StudentViewModel>

<table class="table table-bordered">
    <tr>
        <td>操作</td>
        <td>@Html.DisplayNameFor(m => m.Id)</td>
        <td>@Html.DisplayNameFor(m => m.Name)</td>
        <td>@Html.DisplayNameFor(m => m.Age)</td>
        <td>@Html.DisplayNameFor(m => m.Sex)</td>
    </tr>
    @foreach (StudentViewModel stu in Model)
    {
        <tr>
            <td>
                <a asp-controller="Student" asp-action="Edit" asp-route-id="@stu.Id" >編輯</a>
            </td>
            <td>@Html.DisplayFor(m => stu.Id)</td>
            <td>@Html.DisplayFor(m => stu.Name)</td>
            <td>@Html.DisplayFor(m => stu.Age)</td>
            @*<td>@Html.DisplayFor(m => stu.Sex)</td>*@
            @*<td>@(stu.Sex ? "男" : "女")</td>*@
            <td>@Html.DisplayFor(m=>stu.StrSex)</td>
        </tr>
    }
</table>

Edit.cshtml

@{
    ViewData["Title"] = "編輯學生資訊";
}
@model StudentViewModel

<h3>@ViewData["Title"]</h3>

<form method="post" asp-controller="Student" asp-action="Edit">
    <div>        
        <div class="form-group col-4">
            <label asp-for="Name"></label>
            <input asp-for="Name" class="form-control" />
            <span asp-validation-for="Name"></span>
        </div>
        <div class="form-group col-4">
            <label asp-for="Age"></label>
            <input asp-for="Age" class="form-control" />
            <span asp-validation-for="Age"></span>
        </div>
        <div class="form-group col-4">
            <label asp-for="Sex"></label>
            <input type="radio" asp-for="Sex" value="true" checked="checked" />男
            <input type="radio" asp-for="Sex" value="false" />女
            <span asp-validation-for="Sex"></span>
        </div>
        <div class="form-group col-4">
            <input type="submit" value="更新" class="btn btn-primary" />
        </div>
    </div>
</form>
@section scripts{
    @{
        await Html.RenderPartialAsync("_ValidationScriptsPartial");
    }
}

Edit Action

        /// <summary>
        /// 查詢特定單筆資料回填至編輯表單-顯示
        /// </summary>
        /// <param name="id"></param>
        /// <returns></returns>
        [HttpGet]
        public async Task<IActionResult> Edit(string id)
        {
            if (string.IsNullOrEmpty(id))
            {
                return new StatusCodeResult(400);
            }
            var student = await _dbContext.Students.AsNoTracking().FirstOrDefaultAsync(stu => stu.Id == new Guid(id));
            StudentViewModel vm_Student = new StudentViewModel();
            vm_Student.Id = student.Id;
            vm_Student.Name = student.Name;
            vm_Student.Age = student.Age;
            vm_Student.Sex = student.Sex;
            return View(vm_Student);
        }

        /// <summary>
        /// 編輯更新學生資料-提交
        /// </summary>
        /// <param name="model"></param>
        /// <returns></returns>
        [HttpPost]
        public async Task<IActionResult> Edit(StudentViewModel model)
        {
            if (ModelState.IsValid)
            {
                StudentDataModel studentData = new StudentDataModel()
                {
                    Id = model.Id,
                    Name = model.Name,
                    Age = model.Age,
                    Sex = model.Sex
                };

                _dbContext.Update(studentData);
                await _dbContext.SaveChangesAsync();
                return RedirectToAction(nameof(Show));
            }
            return View(model);
        }

這裡_dbContext.Students.AsNoTracking()

使用的無追蹤模式可以讓查詢資料不會被快取在DbContext實體裡，因此

資料不會被列入追蹤(Tracking)，可直接從DB撈取最新資料不經過cache區域。

在EF 或 EF Core框架中都有Tracking , Non-Tracking模式的區別，預設都會是採用Tracking的模式，因此所有query回傳的entity types結果都會持續被追蹤狀態是否有異動更新。

適用時機:針對read-only情境操作

(PS:用AsNoTracking查出來實體資料是無法透過DbContext的SaveChanges()方法來進行DB資料異動的，因此若是有要做資料異動情況就要觀察一下是否不要用AsNoTracking()了。)

效果

比方我要修改Ted年齡改為35

跳到編輯頁調整年齡後提交導向Show

就可成功和DB連動作更新後資料的呈現了

刪除學生資訊

刪除的操作會分兩種

1.邏輯刪除:只是從table中做一個刪除標記，並未從table中刪掉，可以恢復。

2.物理刪除:直接從DB中將該筆Record刪除。

一般的刪除邏輯是去根據Id在資料表中對應進行的，而EF Core中則是去找到該單個entity做刪除。

Show.cshtml

@{
    ViewData["Title"] = "顯示學生資訊";
}

<h3>@ViewData["Title"]</h3>

@model IEnumerable<StudentViewModel>

<table class="table table-bordered">
    <tr>
        <td>操作</td>
        <td>@Html.DisplayNameFor(m => m.Id)</td>
        <td>@Html.DisplayNameFor(m => m.Name)</td>
        <td>@Html.DisplayNameFor(m => m.Age)</td>
        <td>@Html.DisplayNameFor(m => m.Sex)</td>
    </tr>
    @foreach (StudentViewModel stu in Model)
    {
        <tr>
            <td>
                <a asp-controller="Student" asp-action="Edit" asp-route-id="@stu.Id">編輯</a>
                <a asp-controller="Student" asp-action="Delete" asp-route-id="@stu.Id" onclick="return confirm('是否刪除?')">刪除</a>
            </td>
            <td>@Html.DisplayFor(m => stu.Id)</td>
            <td>@Html.DisplayFor(m => stu.Name)</td>
            <td>@Html.DisplayFor(m => stu.Age)</td>
            @*<td>@Html.DisplayFor(m => stu.Sex)</td>*@
            @*<td>@(stu.Sex ? "男" : "女")</td>*@
            <td>@Html.DisplayFor(m=>stu.StrSex)</td>
        </tr>
    }
</table>

StudentController.cs新增Delete action

using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using Net5EFCore_App1.Data;
using Net5EFCore_App1.Models;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace Net5EFCore_App1.Controllers
{
    public class StudentController : Controller
    {
        private readonly MyTestDbContext _dbContext;
        /// <summary>
        /// 透過建構子注入DbContext
        /// </summary>
        /// <param name="dbContext"></param>
        public StudentController(MyTestDbContext dbContext)
        {
            _dbContext = dbContext;
        }

        /// <summary>
        /// 增加學生資訊的頁面-顯示
        /// </summary>
        /// <returns></returns>
        [HttpGet]
        public IActionResult Add()
        {
            return View();
        }

        /// <summary>
        /// 增加學生資訊的頁面-提交
        /// </summary>
        /// <param name="model"></param>
        /// <returns></returns>
        [HttpPost]
        public IActionResult Add(StudentDataModel model)
        {
            if (ModelState.IsValid)
            {
                StudentDataModel studentData = new StudentDataModel();
                studentData.Id = Guid.NewGuid();
                studentData.Name = model.Name;
                studentData.Age = model.Age;
                studentData.Sex = model.Sex;

                _dbContext.Add(studentData);
                _dbContext.SaveChanges();
                return RedirectToAction("Show");
            }
            return View(model);
        }

        /// <summary>
        /// 顯示查詢出來的學生資訊
        /// </summary>
        /// <returns></returns>
        [HttpGet]
        public async Task<IActionResult> Show()
        {
            var students = await _dbContext.Students.ToListAsync();
            var vm_Student = new List<StudentViewModel>();
            foreach (var stu in students)
            {
                vm_Student.Add(new StudentViewModel() { Id = stu.Id, Name = stu.Name, Age = stu.Age, Sex = stu.Sex, StrSex = stu.Sex ? "男" : "女" });
            }
            return View(vm_Student);
        }

        /// <summary>
        /// 查詢特定單筆資料回填至編輯表單-顯示
        /// </summary>
        /// <param name="id"></param>
        /// <returns></returns>
        [HttpGet]
        public async Task<IActionResult> Edit(string id)
        {
            if (string.IsNullOrEmpty(id))
            {
                return new StatusCodeResult(400);
            }
            var student = await _dbContext.Students.AsNoTracking().FirstOrDefaultAsync(stu => stu.Id == new Guid(id));
            StudentViewModel vm_Student = new StudentViewModel();
            vm_Student.Id = student.Id;
            vm_Student.Name = student.Name;
            vm_Student.Age = student.Age;
            vm_Student.Sex = student.Sex;
            return View(vm_Student);
        }

        /// <summary>
        /// 編輯更新學生資料-提交
        /// </summary>
        /// <param name="model"></param>
        /// <returns></returns>
        [HttpPost]
        public async Task<IActionResult> Edit(StudentViewModel model)
        {
            if (ModelState.IsValid)
            {
                StudentDataModel studentData = new StudentDataModel()
                {
                    Id = model.Id,
                    Name = model.Name,
                    Age = model.Age,
                    Sex = model.Sex
                };

                _dbContext.Update(studentData);
                await _dbContext.SaveChangesAsync();
                return RedirectToAction(nameof(Show));
            }
            return View(model);
        }

        /// <summary>
        /// 刪除學生資料
        /// </summary>
        /// <param name="id"></param>
        /// <returns></returns>
        [HttpGet]
        public async Task<IActionResult> Delete(string id)
        {
            if (string.IsNullOrEmpty(id))
            {
                return new StatusCodeResult(400);
            }

            var student = _dbContext.Students.Find(new Guid(id));
            _dbContext.Remove(student);
            await _dbContext.SaveChangesAsync();
            return RedirectToAction(nameof(Show));
        }
    }
}