代码完成到4.5

第四章/EFCore实体配置DataAnnotations/Author.cs

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+class Author
+{
+    public Guid Id { get; set; }
+    public string Name { get; set; }
+}

第四章/EFCore实体配置DataAnnotations/Book.cs

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+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+
+[Table("T_Books")]
+public class Book
+{
+    public long Id { get; set; }//主键
+    [MaxLength(50)]
+    [Required]
+    public string Title { get; set; }//标题
+    public DateTime PubTime { get; set; }//发布日期
+    public double Price { get; set; }//单价
+    [MaxLength(20)]
+    [Required]
+    public string AuthorName { get; set; }//作者名字
+}

第四章/EFCore实体配置DataAnnotations/EFCore实体配置DataAnnotations.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+	<ItemGroup>
+		<PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="6.0.0" />
+		<PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="6.0.0">
+			<PrivateAssets>all</PrivateAssets>
+			<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+		</PackageReference>
+	</ItemGroup>
+</Project>

第四章/EFCore实体配置DataAnnotations/Migrations/20211110021152_AddAuthor.cs

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+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace EFCore实体配置DataAnnotations.Migrations
+{
+    public partial class AddAuthor : Migration
+    {
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateTable(
+                name: "Authors",
+                columns: table => new
+                {
+                    Id = table.Column<Guid>(type: "uniqueidentifier", nullable: false),
+                    Name = table.Column<string>(type: "nvarchar(max)", nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_Authors", x => x.Id);
+                });
+
+            migrationBuilder.CreateTable(
+                name: "T_Books",
+                columns: table => new
+                {
+                    Id = table.Column<long>(type: "bigint", nullable: false)
+                        .Annotation("SqlServer:Identity", "1, 1"),
+                    Title = table.Column<string>(type: "nvarchar(50)", maxLength: 50, nullable: false),
+                    PubTime = table.Column<DateTime>(type: "datetime2", nullable: false),
+                    Price = table.Column<double>(type: "float", nullable: false),
+                    AuthorName = table.Column<string>(type: "nvarchar(20)", maxLength: 20, nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_T_Books", x => x.Id);
+                });
+        }
+
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "Authors");
+
+            migrationBuilder.DropTable(
+                name: "T_Books");
+        }
+    }
+}

第四章/EFCore实体配置DataAnnotations/Migrations/TestDbContextModelSnapshot.cs

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+// <auto-generated />
+using System;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Metadata;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+
+#nullable disable
+
+namespace EFCore实体配置DataAnnotations.Migrations
+{
+    [DbContext(typeof(TestDbContext))]
+    partial class TestDbContextModelSnapshot : ModelSnapshot
+    {
+        protected override void BuildModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder
+                .HasAnnotation("ProductVersion", "6.0.0")
+                .HasAnnotation("Relational:MaxIdentifierLength", 128);
+
+            SqlServerModelBuilderExtensions.UseIdentityColumns(modelBuilder, 1L, 1);
+
+            modelBuilder.Entity("Author", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uniqueidentifier");
+
+                    b.Property<string>("Name")
+                        .IsRequired()
+                        .HasColumnType("nvarchar(max)");
+
+                    b.HasKey("Id");
+
+                    b.ToTable("Authors");
+                });
+
+            modelBuilder.Entity("Book", b =>
+                {
+                    b.Property<long>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint");
+
+                    SqlServerPropertyBuilderExtensions.UseIdentityColumn(b.Property<long>("Id"), 1L, 1);
+
+                    b.Property<string>("AuthorName")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("nvarchar(20)");
+
+                    b.Property<double>("Price")
+                        .HasColumnType("float");
+
+                    b.Property<DateTime>("PubTime")
+                        .HasColumnType("datetime2");
+
+                    b.Property<string>("Title")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("nvarchar(50)");
+
+                    b.HasKey("Id");
+
+                    b.ToTable("T_Books");
+                });
+#pragma warning restore 612, 618
+        }
+    }
+}

第四章/EFCore实体配置DataAnnotations/Program.cs

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+/*
+using TestDbContext ctx = new TestDbContext();
+Book b = new Book { AuthorName = "Bill Gates", Title = "Zack, Cool guy!", 
+    Price = 9.9, PubTime = new DateTime(2020, 12, 30) };
+ctx.Books.Add(b);
+Console.WriteLine($"保存前，Id={b.Id}");
+await ctx.SaveChangesAsync();
+Console.WriteLine($"保存后，Id={b.Id}");*/
+/*
+using TestDbContext ctx = new TestDbContext() ;
+Console.WriteLine("****1*****");
+Author a1 = new Author { Name = "杨中科" };
+Console.WriteLine($"Add前，Id={a1.Id}");
+ctx.Authors.Add(a1);
+Console.WriteLine($"Add后，保存前，Id={a1.Id}");
+await ctx.SaveChangesAsync();
+Console.WriteLine($"保存后，Id={a1.Id}");
+Console.WriteLine("****2*****");
+Author a2 = new Author { Name = "Zack Yang" };
+a2.Id = Guid.NewGuid();
+Console.WriteLine($"保存前，Id={a2.Id}");
+ctx.Authors.Add(a2);
+await ctx.SaveChangesAsync();
+Console.WriteLine($"保存前，Id={a2.Id}");*/
+using TestDbContext ctx = new TestDbContext();
+var books = ctx.Books.Where(b => b.PubTime.Year > 2010).Take(3);
+foreach (var b in books)
+{
+ Console.WriteLine(b.Title);
+}

第四章/EFCore实体配置DataAnnotations/TestDbContext.cs

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+using Microsoft.EntityFrameworkCore;
+class TestDbContext : DbContext
+{
+    public DbSet<Book> Books { get; set; }
+    public DbSet<Author> Authors { get; set; }
+    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
+    {
+        string connStr = "Server=.;Database=demo2;Trusted_Connection=True";
+        optionsBuilder.UseSqlServer(connStr);
+        optionsBuilder.LogTo(Console.WriteLine);
+    }
+
+    protected override void OnModelCreating(ModelBuilder modelBuilder)
+    {
+        base.OnModelCreating(modelBuilder);
+        modelBuilder.ApplyConfigurationsFromAssembly(this.GetType().Assembly);
+    }
+}

第四章/MySQL版项目/Book.cs

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+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+
+[Table("T_Books")]
+public class Book
+{
+    public long Id { get; set; }//主键
+    [MaxLength(50)]
+    [Required]
+    public string Title { get; set; }//标题
+    public DateTime PubTime { get; set; }//发布日期
+    public double Price { get; set; }//单价
+    [MaxLength(20)]
+    [Required]
+    public string AuthorName { get; set; }//作者名字
+}

第四章/MySQL版项目/MySQL版项目.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+	<ItemGroup>
+		<PackageReference Include="Pomelo.EntityFrameworkCore.MySql" Version="6.0.0" />
+		<PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="6.0.0">
+			<PrivateAssets>all</PrivateAssets>
+			<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+		</PackageReference>
+	</ItemGroup>
+</Project>

第四章/MySQL版项目/Program.cs

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+using TestDbContext ctx = new TestDbContext();
+var books = ctx.Books.Where(b => b.PubTime.Year > 2010).Take(3);
+foreach (var b in books)
+{
+    Console.WriteLine(b.Title);
+}

第四章/MySQL版项目/TestDbContext.cs

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+using Microsoft.EntityFrameworkCore;
+class TestDbContext : DbContext
+{
+    public DbSet<Book> Books { get; set; }
+    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
+    {
+        optionsBuilder.UseMySql("server=localhost;user=root;password=adfa3_ioz09_08nljo;database=ef",
+            new MySqlServerVersion(new Version(8, 6, 20)));
+        optionsBuilder.LogTo(Console.WriteLine);
+    }
+
+    protected override void OnModelCreating(ModelBuilder modelBuilder)
+    {
+        base.OnModelCreating(modelBuilder);
+        modelBuilder.ApplyConfigurationsFromAssembly(this.GetType().Assembly);
+    }
+}

第四章/PostgreSQL版项目/Book.cs

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+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+
+[Table("T_Books")]
+public class Book
+{
+    public long Id { get; set; }//主键
+    [MaxLength(50)]
+    [Required]
+    public string Title { get; set; }//标题
+    public DateTime PubTime { get; set; }//发布日期
+    public double Price { get; set; }//单价
+    [MaxLength(20)]
+    [Required]
+    public string AuthorName { get; set; }//作者名字
+}

第四章/PostgreSQL版项目/PostgreSQL版项目.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+	<ItemGroup>
+		<PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="6.0.0" />
+		<PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="6.0.0">
+			<PrivateAssets>all</PrivateAssets>
+			<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+		</PackageReference>
+	</ItemGroup>
+</Project>

第四章/PostgreSQL版项目/Program.cs

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+using TestDbContext ctx = new TestDbContext();
+var books = ctx.Books.Where(b => b.PubTime.Year > 2010).Take(3);
+foreach (var b in books)
+{
+    Console.WriteLine(b.Title);
+}