使用EntityFramework Core和Enums作为字符串的ASP.NET Core Razor页面——第三部分

介绍

使用代码

添加项目和项目状态处理

下载源文件 - 989.1 KB

介绍

这是一篇由多部分组成的文章的第三部分，演示了通过EntityFramework Core 2.1（EF）将C＃enum值映射到数据库表中的string值。它解决了enum与应用程序实体的一对多和多对多关系中的值映射问题。它在ASP.NET Core Razor Page应用程序的上下文中执行此操作。

EF是对象关系映射器（ORM）。在诸如此示例的应用程序中，有两个“世界”。一个是在C＃中作为对象模型存在的对象世界。另一个是存在于关系数据库中的关系世界，如Microsoft SQL Server。这两个世界并不一致。ORM的功能，如EntityFramework，就是这两个世界之间的桥梁，并促进它们之间的数据传输。

第一部分。设置实体框架数据上下文和初始Customer的Razor页面

第二部分。完成了Customers的CRUD功能

在第三部分。我们将创建Project和ProjectState实体并在ProjectState和Project之间实现一个一对多的关系，如下：

添加Project，ProjectState和ProjectStateDescription实体。
添加EF迁移以在数据库中创建和配置Projects和ProjectStateDescriptions表。
演示enum对象模型实体中的string值与Projects和ProjectStateDescriptions数据库表中的值之间的转换。
搭建，实现和测试包含ProjectState功能的ProjectCRUD页面，如CustomerProjects.cshtml，CustomerProjectCreate.cshtml，CustomerProjectDetails.cshtml和CustomerProjectDelete.cshtml Razor页面。

使用代码

添加初始项目处理。

接下来，我们启用Customer项目处理。该应用程序使用Customer作为“网关”实体; 一切都是通过Customer。Customer和Projects之间存在一对多的关系。因此，我们需要修改Customer类。

修改后的Customer.cs：

using System.Collections.Generic;

namespace QuantumWeb.Model
{
    ////// Customer Class
    ///public class Customer
    {
        #region Constructors

        ////// Parameter-less Constructor
        ///////// Required for scaffolding the UI
        ///public Customer()
        {
        } // end public Customer()

        #endregion // Constructors

        ////// Customer Identifier, primary key
        ///public int CustomerId { get; set; }
        ////// Customer Name
        ///public string CustomerName { get; set; }
        ////// Primary Customer Contact
        ///public string CustomerContact { get; set; }
        ////// Customer Contact Phone Number
        ///public string CustomerPhone { get; set; }
        ////// Customer Contact Email Address
        ///public string CustomerEmail { get; set; }

        #region Navigation Properties

        ////// List of Projects
        ///public ListProjects { get; set; }

        #endregion // Navigation Properties

    } // end public class Customer

} // end namespace QuantumWeb.Model

我们添加了一个项目列表。在这里，我们将某些属性标识为导航属性。这些属性引用其他类/实体，以便我们可以在处理中导航到它们。Customer在Projects列表中表示零或多个Projects。初始Project类定义如下。

初始Project.cs：

namespace QuantumWeb.Model
{
    ////// Project Class
    ///public class Project
    {
        ////// Project Identifier, primary key
        ///public int ProjectId { get; set; }
        ////// Project Name
        ///public string ProjectName { get; set; }

        #region Navigation Properties

        ////// Customer Identifier
        ///public int CustomerId { get; set; }

        ////// Customer
        ///////// Every Project has a Customer
        ///public Customer Customer { get; set; }

        ////// Project Status Code
        ///public ProjectState ProjectStateCode { get; set; }

        ////// ProjectStateDescription Reference
        ///public ProjectStateDescription ProjectStateDescription { get; set; }

        #endregion // Navigation Properties

    } // end public class Project

} // end namespace QuantumApp.Model

除了定义初始化Project类之外，我们还将在Model文件夹中定义ProjectState enum。

ProjectState.cs：

namespace QuantumWeb.Model
{   
    ////// Project State Enumeration
    ///public enum ProjectState
    {
        Prospect,
        UnderReview,
        StartScheduled,
        InProgress,
        Completed
    } // end public enum ProjectState

} // end namespace QuantumWeb.Model

这个enum指定了Project工作流的状态。

Prospect。这涉及一个有前景的Project。这个Project可能是通过推荐或其他营销工作提出的。尚未进行任何研究，且规格尚不清楚。
UnderReview。在这种状态下，Project制定了要求，初始预算和进度表。没有承诺Quantum或者Customer。
StartScheduled。已经指定了工作开始的日期，并且正在准备开始工作。
InProgress。实际工作已经开始但尚未完成。
Completed。项目工作完成。

如前所述，我们对此应用程序有两个目标。

我们应该为Project将在UI中显示的每个状态定义简短描述，以帮助用户理解每个状态的含义。
每个enum值都作为string类型存储在数据库中。

为了满足ProjectState enum的这些要求，我们定义了ProjectStateDescription类。

ProjectStateDescription.cs：

using System.Collections.Generic;

namespace QuantumWeb.Model
{
    ////// Project State Description Class
    ///public class ProjectStateDescription
    {
        ////// ProjectState Code
        ///public ProjectState ProjectStateCode { get; set; }

        ////// State Description
        ///public string StateDescription { get; set; }

        #region Navigation Properties

        ////// Projects Collection
        ///public ListProjects { get; set; }

        #endregion // Navigation Properties

    } // end public class ProjectStateDescription

} // end namespace QuantumWeb.Model

ProjectState对Projects的一对多的关系，通过导航属性启用。每个Project都有一个ProjectStateDesciption。每个ProjectStateDescripton都有一个Projects集合。

接下来，我们需要为Project和ProjectStateDescription定义EF配置类，并在QuantumDbContext类中包含所有内容。所有此活动都发生在Data文件夹中。

初始ProjectConfiguration.cs：

using System;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Metadata.Builders;
using QuantumWeb.Model;

namespace QuantumWeb.Data
{
    public class ProjectConfiguration : IEntityTypeConfiguration{
        public void Configure(EntityTypeBuilderbuilder)
        {
            builder.ToTable("Projects");
            builder.HasKey(p => p.ProjectId);
            builder.Property(p => p.ProjectId)
            .HasColumnType("int");
            builder.Property(p => p.ProjectName)
            .IsRequired()
            .HasColumnType("nvarchar(80)")
            .HasMaxLength(80);
            builder.Property(p => p.CustomerId)
            .HasColumnType("int")
            .IsRequired();
            builder.HasOne(p => p.Customer)
            .WithMany(c => c.Projects)
            .HasForeignKey(p => p.CustomerId)
            .IsRequired();
            builder.Property(p => p.ProjectStateCode)
            .HasColumnType("nvarchar(15)")
            .HasDefaultValue(ProjectState.Prospect)
            .HasConversion(
                p => p.ToString(),
                p => (ProjectState)Enum.Parse(typeof(ProjectState), p));
            builder.HasOne(p => p.ProjectStateDescription)
            .WithMany(pd => pd.Projects)
            .HasForeignKey(p => p.ProjectStateCode);
        } // end public void Configure(EntityTypeBuilderbuilder)

    } // end public class ProjectConfiguration : IEntityTypeConfiguration} // end namespace QuantumWeb.Data

看看下面提取的行：

builder.HasOne(p => p.Customer)
.WithMany(c => c.Projects)
.HasForeignKey(p => p.CustomerId)
.IsRequired();

对这些行的解释是，“每个Project都有一个带有许多Projects的Customer。每个Project都映射到Projects数据库中的表，通过外键CustomerId，并且这是必需的。因此，Customer- Project关系是一对多。

在一对多ProjectStateDescription- Project关系被配置为：

builder.HasOne(p => p.ProjectStateDescription)
.WithMany(pd => pd.Projects)
.HasForeignKey(p => p.ProjectStateCode);

接下来，我们将了解处理enum的值到数据库string列配置的方式。

builder.Property(p => p.ProjectStateCode)
.HasColumnType("nvarchar(15)")
.HasDefaultValue(ProjectState.Prospect)
.HasConversion(
    p => p.ToString(),
    p => (ProjectState)Enum.Parse(typeof(ProjectState), p));

这些行首先在Projects名为的表中配置一个列ProjectStateCode，类型为nvarchar(15),其默认值来自ProjectState.Prospect。接下来，定义ProjectState值和string值之间的转换。当将值从ProjectState enum移动到Projects表时，将使用该ToString()函数转换值。换另一种方式时，表中string的值将被解析为一个enum值。始终使用相同的方案在数据库列中的enum值和string值之间进行转换。

ProjectStateDescriptionConfiguration类如下所示。

ProjectStateDescriptionConfiguration.cs：

using System;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Metadata.Builders;
using QuantumWeb.Model;

namespace QuantumWeb.Data
{
    ////// ProjectState Description Configuration Class
    ///public class ProjectStateDescriptionConfiguration : 
                   IEntityTypeConfiguration{

        public void Configure(EntityTypeBuilderbuilder)
        {
            builder.ToTable("ProjectStateDescriptions");
            builder.HasKey(p => p.ProjectStateCode);
            builder.Property(p => p.ProjectStateCode)
            .HasColumnType("nvarchar(15)")
            .HasConversion(
                p => p.ToString(),
                p => (ProjectState)Enum.Parse(typeof(ProjectState), p));
            builder.Property(p => p.StateDescription)
            .IsRequired()
            .HasColumnType("nvarchar(80)")
            .HasMaxLength(80);
        } // end public void Configure(EntityTypeBuilderbuilder)

    } // end public class ProjectStateDescriptionConfiguration : 
      // IEntityTypeConfiguration} // end namespace QuantumWeb.Data

现在，我们更新QuantumDbContext类。

然后更新QuantumDbContext.cs：

using Microsoft.EntityFrameworkCore;
using QuantumWeb.Model;

namespace QuantumWeb.Data
{
    public class QuantumDbContext : DbContext
    {
        public QuantumDbContext (DbContextOptionsoptions)
            : base(options)
        {
        } // end public QuantumDbContext (DbContextOptionsoptions)

        #region DbSets

        ////// Customer DbSet
        ///public DbSetCustomers { get; set; }

        ////// Project DbSet
        ///public DbSetProjects { get; set; }

        ////// ProjectStateDescription DbSet
        ///public DbSetProjectStateDescriptions { get; set; }

        #endregion // DbSets

        ////// Data Model Creation Method
        //////ModelBuilder instanceprotected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.ApplyConfiguration(new CustomerConfiguration());
            modelBuilder.ApplyConfiguration(new ProjectConfiguration());
            modelBuilder.ApplyConfiguration(new ProjectStateDescriptionConfiguration());
        } // end  protected override void OnModelCreating(ModelBuilder modelBuilder)

    } // end public class QuantumDbContext : DbContext

} // end namespace QuantumWeb.Data

现在为Project和ProjectState实体添加EF迁移。(译者注：同样需要调整appsettings.json中数据库连接字符串，建议删除Migrations文件夹后在执行下面的命令，同时提醒，在执行下面命令后需要命令update-database更新到数据库)

Add-Migration Added-Project-ProjectState

生成 ~\Migrations\20181021203503_Added-Project-ProjectState.cs:

using Microsoft.EntityFrameworkCore.Metadata;
using Microsoft.EntityFrameworkCore.Migrations;

namespace QuantumWeb.Migrations
{
    public partial class AddedProjectProjectState : Migration
    {
        protected override void Up(MigrationBuilder migrationBuilder)
        {
            migrationBuilder.CreateTable(
                name: "ProjectStateDescriptions",
                columns: table => new
                {
                    ProjectStateCode = 
                    table.Column(type: "nvarchar(15)", nullable: false),
                    StateDescription = 
                    table.Column(type: "nvarchar(80)", maxLength: 80, nullable: false)
                },
                constraints: table =>
                {
                    table.PrimaryKey("PK_ProjectStateDescriptions", x => x.ProjectStateCode);
                });

            migrationBuilder.CreateTable(
                name: "Projects",
                columns: table => new
                {
                    ProjectId = table.Column(type: "int", nullable: false)
                        .Annotation("SqlServer:ValueGenerationStrategy", 
                        SqlServerValueGenerationStrategy.IdentityColumn),
                    ProjectName = table.Column(type: "nvarchar(80)", 
                                  maxLength: 80, nullable: false),
                    CustomerId = table.Column(type: "int", nullable: false),
                    ProjectStateCode = table.Column(type: "nvarchar(15)", nullable: false, defaultValue: "Prospect")
                },
                constraints: table =>
                {
                    table.PrimaryKey("PK_Projects", x => x.ProjectId);
                    table.ForeignKey(
                        name: "FK_Projects_Customers_CustomerId",
                        column: x => x.CustomerId,
                        principalTable: "Customers",
                        principalColumn: "CustomerId",
                        onDelete: ReferentialAction.Cascade);
                    table.ForeignKey(
                        name: "FK_Projects_ProjectStateDescriptions_ProjectStateCode",
                        column: x => x.ProjectStateCode,
                        principalTable: "ProjectStateDescriptions",
                        principalColumn: "ProjectStateCode",
                        onDelete: ReferentialAction.Cascade);
                });

            migrationBuilder.CreateIndex(
                name: "IX_Projects_CustomerId",
                table: "Projects",
                column: "CustomerId");

            migrationBuilder.CreateIndex(
                name: "IX_Projects_ProjectStateCode",
                table: "Projects",
                column: "ProjectStateCode");
        }

        protected override void Down(MigrationBuilder migrationBuilder)
        {
            migrationBuilder.DropTable(
                name: "Projects");

            migrationBuilder.DropTable(
                name: "ProjectStateDescriptions");
        }
    }
}

在Update- Database命令之后，SQL Server Management Studio（SSMS）中的数据库关系图如下所示。

使用Customer- Project- ProjectState表的QuantumDbContext数据库关系图：

修改Project和ProjectState的Razor 页。

我们需要为项目的应用程序添加一些自定义客户Razor 页面。首先，我们需要为CustomerProjects添加一个指向Customer/Index页面的链接。

添加CustomerProjects 链接指向Pages\Customers\Index.cshtml:

@page
@model QuantumWeb.Pages.Customers.IndexModel

@{
    ViewData["Title"] = "Index";
}
		
			Index
		

		
			Create New 
		
@foreach (var item in Model.Customer) {}
		
			
			
				
				
					
					
						@Html.DisplayNameFor(model => model.Customer[0].CustomerName)
					

					
						@Html.DisplayNameFor(model => model.Customer[0].CustomerContact)
					

					
						@Html.DisplayNameFor(model => model.Customer[0].CustomerPhone)
					

					
						@Html.DisplayNameFor(model => model.Customer[0].CustomerEmail)
					

					
						
					

				

			

			
				
				
					
					
						@Html.DisplayFor(modelItem => item.CustomerName)
					

					
						@Html.DisplayFor(modelItem => item.CustomerContact)
					

					
						@Html.DisplayFor(modelItem => item.CustomerPhone)
					

					
						@Html.DisplayFor(modelItem => item.CustomerEmail)
					

					
						Edit |
                 Details |
                 Projects |
                 Delete

我们将如下构建几个自定义Customers Razor页面。

为客户设计的定制构建Razor页面：

搭建Customers/CustomerProjects Razor 页面：

单击“ 添加 ”将为CustomerProjects Index页面生成shell文件。

生成~Pages\Customers\CustomerProjects.cshtml

@page
@model QuantumWeb.Pages.Customers.CustomerProjectsModel
@{
    ViewData["Title"] = "CustomerProjects";
}
		
			CustomerProjects

生成~Pages\Customers\CustomerProjects.cshtml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;

namespace QuantumWeb.Pages.Customers
{
    public class CustomerProjectsModel : PageModel
    {
        public void OnGet()
        {

        }
    }
}

我们将在每种情况下修改这些shell文件以满足我们的需求。CustomerProjects Index 页面的修改文件。

修改了~Pages\Customers\CustomerProjects.cshtml

@page "{id:int?}"
@model QuantumWeb.Pages.Customers.CustomerProjectsModel
@{
    ViewData["Title"] = "Customer Projects";
}
		
			Customer Projects
		

		
			
			
				Customer
			

			
			@Html.DisplayNameFor(model => model.Customer.CustomerId)@Html.DisplayFor(model => model.Customer.CustomerId)@Html.DisplayNameFor(model => model.Customer.CustomerName)@Html.DisplayFor(model => model.Customer.CustomerName)@Html.DisplayNameFor(model => model.Customer.Projects)@foreach (var item in Model.Customer.Projects)
                {}
			
				
				
					
					
						
						
							Project ID
						

						
							Project Name
						

						
							Project State
						

						
							
						

					

					
						
						
							@Html.DisplayFor(modelItem => item.ProjectId)
						

						
							@Html.DisplayFor(modelItem => item.ProjectName)
						

						
							@Html.DisplayFor(modelItem => item.ProjectStateCode)
						

						
							Edit | Delete 
						

					

				

			

		

		
			 Create New Project | Back to List

“ {id:int?}”表示需要整数参数，id需要或者请求页面将返回HTTP 401（未找到页面）错误。在这种情况下，这是目标Customer的标识符（CustomerId）。另外，请注意引用该CustomerProjectCreate页面的链接。

Create New Project |

这将把我们带到CustomerProjectCreate尚未创建的页面，为引用Customer创建一个新的Project。

修改了~Pages\Customers\CustomerProjects.cshtml.cs

using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;
using Microsoft.EntityFrameworkCore;
using QuantumWeb.Data;
using QuantumWeb.Model;

namespace QuantumWeb.Pages.Customers
{
    public class CustomerProjectsModel : PageModel
    {
        private readonly QuantumDbContext _context;

        public CustomerProjectsModel(QuantumDbContext context)
        {
            _context = context;
        } // end public CustomerProjectsModel(QuantumDbContext context)

        public Customer Customer { get; set; }

        public async TaskOnGet(int? id)
        {
            if (id == null)
            {
                return NotFound();
            } // endif (id == null)

            Customer = await _context.Customers
                .Include(c => c.Projects)
                    .FirstOrDefaultAsync(c => c.CustomerId == id);

            if (Customer == null)
            {
                return NotFound();
            } // endif (Customer == null)

            return Page();
        } // end public async TaskOnGet(int? id)

    } // end public class CustomerProjectsModel : PageModel

} // end namespace QuantumWeb.Pages.Customers

请注意，OnGet处理程序具有可为空的整数参数，id应该是如上所述的CustomerId。

QuantumWeb 应用客户页面： https//localhost: 44306/Customers 具有项目链接。

Customer Projects页面：https//localhost: 44306/Customers/CustomerProjects/1（无项目）

“ 创建新项目 ”链接将激活自定义CustomerProjectCreate Razor页面。我们现在搭建这个页面。

搭建Customers/CustomerProjectCreate Razor页面：

Initial~Pages\Customers\CustomerProjectCreate.cshtml.cs

using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.EntityFrameworkCore;
using QuantumWeb.Data;
using QuantumWeb.Model;

namespace QuantumWeb.Pages.Customers
{
    public class CustomerProjectCreateModel : PageModel
    {
        private readonly QuantumDbContext _context;

        public CustomerProjectCreateModel(QuantumDbContext context)
        {
            _context = context;
        } // end public CustomerProjectCreateModel(QuantumContext context)

        [BindProperty]
        public Customer Customer { get; set; }

        public async TaskOnGet(int? id)
        {
            if (id == null)
            {
                return NotFound();
            } // endif (id == null)

            Customer = await _context.Customers
                .Include(c => c.Projects)
                    .FirstOrDefaultAsync(c => c.CustomerId == id);

            if (Customer == null)
            {
                return NotFound();
            } // endif (Customer == null)

            ViewData["ProjectStateCode"] = new SelectList(_context.ProjectStateDescriptions,
                "ProjectStateCode", "StateDescription", ProjectState.Prospect);

            return Page();

        } // end public async TaskOnGet(int? id)

        [BindProperty]
        public Project Project { get; set; }

        public async TaskOnPostAsync()
        {
            if (!ModelState.IsValid)
            {
                return Page();
            } // endif (!ModelState.IsValid)

            Project.CustomerId = Customer.CustomerId;

            _context.Projects.Add(Project);
            await _context.SaveChangesAsync();

            return RedirectToPage("./CustomerProjects", new { id = Customer.CustomerId });
        } // end public async TaskOnPostAsync()

    } // end public class CustomerProjectCreateModel : PageModel

} // end namespace QuantumWeb.Pages.Customers

请注意此代码中的这些行。

[BindProperty]
public Customer Customer { get; set; }

该[BindProperty]将Customer实例绑定到UI的元素，以便在浏览器和Web服务器之间保留它们的值。另请注意，此属性也适用于Project实例。

Customer = await _context.Customers
    .Include(c => c.Projects)
        .FirstOrDefaultAsync(c => c.CustomerId == id);

此语句对数据库执行查询，以检索Customer其主键值CustomerId与输入参数id值及其关联Project记录匹配的记录。如果有，该.Include函数的功能是查询中包含相关记录。

ViewData["ProjectStateCode"] = new SelectList(_context.ProjectStateDescriptions,
   "ProjectStateCode", "StateDescription", ProjectState.Prospect);

ViewData是一个无类型的键值字典，用于在CustomerProjectCreateModel类（在.cshtml.cs文件中）和.cshtml文件中的HTML 之间传递值。这类似于MVC中将数据从Controller 传递到View，在使用ViewData中，数据仅在HTTP请求中持久存在。其成员由ProjectStateDescriptions数据库表中的查询填充。在这种情况下，_context.ProjectStateDescriptions是IEnumerable从查询返回的。ProjectStateCode是表中的主键，表示ViewData字典中的键。StateDescription成为ViewData字典中的关联值。ViewData将用来填充在CustomerProjectCreate.cshtml（见下文）中的元素。ProjectState.Prospect是为从ProjectState enum中默认选择的值。您可以阅读更多ViewData信息在以下链接上 https：//www.tektutorialshub.com/viewbag-viewdata-asp-net-core/。（译者注：需要在ProjectStateDescriptions数据库表中手动加入数据，具体可见下图展示的数据加，ProjectStateCode字段的值就是对应枚举中的值--定义在代码中的名称。如此值为Completed，StateDescription字段值为project is complete，以此类推）

初始化~Pages\ Customers\CustomerProjectCreate.cshtml：

@page
@model QuantumWeb.Pages.Customers.CustomerProjectCreateModel
@{
    ViewData["Title"] = "Create Customer Project";
}
		
			Create Customer Project
		

		
		@Html.DisplayNameFor(model => model.Customer.CustomerId)@Html.DisplayFor(model => model.Customer.CustomerId)@Html.DisplayNameFor(model => model.Customer.CustomerName)@Html.DisplayFor(model => model.Customer.CustomerName)
		
			
			
				
				
					
				

				
					
				

				
					
				

				
					
				

			

		

		
			 Back to Customer Projects  
		
@section Scripts {
    @{await Html.RenderPartialAsync("_ValidationScriptsPartial");}
}

关键要素如下：

这个隐藏捕获目标CustomerId以便在发布时可用它来创建Project。

此元素将显示为UI中的下拉列表，其中包含CustomerProjectCreate.OnGet()方法中ViewData填充的值。

初始化 ~Pages\Customers\CustomerProjectCreate.cshtml：

这将显示最初显示的Customers/CustomerProjectCreate页面。

CustomerProjectCreate 包含数据的页面：

点击“ Create”后，我们会看到：

客户Projects页面添加Project：

接下来的两个图显示了为两个Customers添加其他Projects之后的情况。

客户项目页面包含Mirarex Oil＆Gas的2个项目：

客户项目页面包含Polyolefin Processing, Inc.的3个项目

我们现在可以添加另一个页面来编辑Customer项目，CustomerProjectEdit页面。

搭建 Customers/CustomerProjectEdit Razor Page

初始化~Pages\Customers\CustomerProjectEdit.cshtml.cs

using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.EntityFrameworkCore;
using QuantumWeb.Data;
using QuantumWeb.Model;

namespace QuantumApp.Pages.Customers
{
    public class CustomerProjectEditModel : PageModel
    {
        private readonly QuantumDbContext _context;

        public CustomerProjectEditModel(QuantumDbContext context)
        {
            _context = context;
        } // end public CustomerProjectEditModel(QuantumDbContext context)

        [BindProperty]
        public Customer Customer { get; set; }
        [BindProperty]
        public Project Project { get; set; }

        public async TaskOnGet(int? id)
        {
            if (id == null)
            {
                return NotFound();
            } // endif (id == null)

            Project = await _context.Projects
                .Include(p => p.Customer)
                    .FirstOrDefaultAsync(p => p.ProjectId == id);

            if (Project == null)
            {
                return NotFound();
            } // endif (Project == null)

            Customer = Project.Customer;

            ViewData["ProjectStateCode"] = new SelectList(_context.ProjectStateDescriptions,
                "ProjectStateCode", "StateDescription", ProjectState.Prospect);

            return Page();
        } // end public async TaskOnGet(int? id)

        public async TaskOnPostAsync(int? id)
        {
            if (!ModelState.IsValid)
            {
                return Page();
            } // endif (!ModelState.IsValid)

            var projectToUpdate = await _context.Projects.FindAsync(id);

            if (projectToUpdate == null)
            {
                return NotFound();
            } // endif (projectToUpdate == null)

            projectToUpdate.CustomerId = Customer.CustomerId;

            if (await TryUpdateModelAsync(
                projectToUpdate,
                "project",
                p => p.ProjectName, p => p.ProjectStateCode))
            {
                await _context.SaveChangesAsync();
                return RedirectToPage("./CustomerProjects", new { id = Customer.CustomerId });
            }

            return Page();
        } // end public async TaskOnPostAsync(int? id)

    } // end public class CustomerProjectEditModel : PageModel

} // end namespace QuantumApp.Pages.Customers

此代码与CustomerProjectCreate页面在.Include和ViewData方面具有相同的构件。

初始化~Pages\Customers\CustomerProjectEdit.cshtml

@page "{id:int?}"
@model QuantumWeb.Pages.Customers.CustomerProjectEditModel
@{
    ViewData["Title"] = "Edit Customer Project";
}
		
			Edit Customer Project
		

		
		@Html.DisplayNameFor(model => model.Customer.CustomerId)@Html.DisplayFor(model => model.Customer.CustomerId)@Html.DisplayNameFor(model => model.Customer.CustomerName)@Html.DisplayFor(model => model.Customer.CustomerName)
		
			
			
				
				
					
				

				
					
				

				
					
				

				
					
				

			

		

		
			 Back to Customer Projects  
		
@section Scripts {
    @{await Html.RenderPartialAsync("_ValidationScriptsPartial");}
}

关于CustomerId的隐藏和，此页面具有与CustomerProjectCreate页面相同的元素。

Customer Projects 页面包含Mirarex Oil＆Gas的2个项目——用于编辑：

Mirarex Oil＆Gas, Zolar Pipeline的客户项目编辑页面：

客户项目页面包含Mirarex Oil & Gas 的2个项目——项目编辑：

通过CustomerProjectDelete页面，此项目的最后一个功能是删除。

搭建 Customers/CustomerProjectDelete Razor页面：

初始化~Pages\Customers\CustomerProjectDelete.cshtml.cs

using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;
using Microsoft.EntityFrameworkCore;
using QuantumWeb.Data;
using QuantumWeb.Model;

namespace QuantumWeb.Pages.Customers
{
    public class CustomerProjectDeleteModel : PageModel
    {
        private readonly QuantumDbContext _context;

        public CustomerProjectDeleteModel(QuantumDbContext context)
        {
            _context = context;
        } // end public CustomerProjectDeleteModel(QuantumContext context)

        [BindProperty]
        public Customer Customer { get; set; }
        [BindProperty]
        public Project Project { get; set; }

        public async TaskOnGetAsync(int? id)
        {
            if (id == null)
            {
                return NotFound();
            } // endif (id == null)

            Project = await _context.Projects
                .Include(p => p.Customer)
                    .FirstOrDefaultAsync(p => p.ProjectId == id);

            if (Project == null)
            {
                return NotFound();
            } // endif (Project == null)

            Customer = Project.Customer;

            return Page();
        } // end public async TaskOnGet(int? id)

        public async TaskOnPostAsync(int? id)
        {
            if (id == null)
            {
                return NotFound();
            } // endif (id == null)

            Project = await _context.Projects
                .Include(p => p.Customer)
                .FirstOrDefaultAsync(p => p.ProjectId == id);

            if (Project != null)
            {
                _context.Projects.Remove(Project);
                await _context.SaveChangesAsync();
            } // endif (Project != null)

            return RedirectToPage("./CustomerProjects", new { id = Project.Customer.CustomerId });
        } // end public async TaskOnPostAsync(int? id)

    } // end public class CustomerProjectDeleteModel : PageModel

} // end namespace QuantumWeb.Pages.Customer

初始化~Pages\Customers\CustomerProjectDelete.cshtml

@page "{id:int?}"
@model QuantumWeb.Pages.Customers.CustomerProjectDeleteModel
@{
    ViewData["Title"] = "Delete Customer Project";
}
		
			Delete Customer Project
		

		
			Are you sure you want to delete this?
		

		
			@Html.DisplayNameFor(model => model.Customer.CustomerName)@Html.DisplayFor(model => model.Customer.CustomerName)@Html.DisplayNameFor(model => model.Project.ProjectId)@Html.DisplayFor(model => model.Project.ProjectId)@Html.DisplayNameFor(model => model.Project.ProjectName)@Html.DisplayFor(model => model.Project.ProjectName)@Html.DisplayNameFor(model => model.Project.ProjectStateCode)@Html.DisplayFor(model => model.Project.ProjectStateCode) Back to Customer Projects  |

客户项目页面包含Mirarex Oil & Gas的3个项目：

删除客户项目页面——删除Ouachita Shale：

客户项目页面包含Mirarex Oil＆Gas的2个项目：

此时，我们可以总结下表中的测试数据：

Customers, Projects, ProjectStates

CustomerId

Customer Name

ProjectId

Project Name

ProjectStateCode

StateDescription

Mirarex Oil & Gas, LLC

Zolar Pipeline

UnderReview

Project is under review and negotiation

Mirarex Oil & Gas, LLC

Nelar Ranch Gas Fracturing

Prospect

Prospective or referred project

Polyolefin Processing, Inc.

Port Gibson Plant Expansion

Prospect

Prospective or referred project

Polyolefin Processing, Inc.

Jackson Plant Control System Upgrade

Prospect

Prospective or referred project

Polyolefin Processing, Inc.

Eutaw Plant Shutdown & Maintenance

Prospect

Prospective or referred project

下面可以进入第四部分进行学习。

原文地址：https://www.codeproject.com/Articles/1264330/ASP-NET-Core-Razor-Pages-Using-EntityFramework-C-2

使用EntityFramework Core和Enums作为字符串的ASP.NET Core Razor页面——第三部分

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