时间：2021-07-01 10:21:17 帮助过：16人阅读
public class EfDbContext : DbContext { /// <summary> /// 指定静态ILoggerFactory /// </summary> public static readonly ILoggerFactory MyLoggerFactory = LoggerFactory.Create(builder => { builder.AddConsole(); }); public EfDbContext() { } public EfDbContext(DbContextOptions<EfDbContext> options) : base(options) { } private string Conn = null; public DbContext ToWriteOrRead(string conn) { Conn = conn; return this; } protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder) { if (!optionsBuilder.IsConfigured) { optionsBuilder.UseLoggerFactory(MyLoggerFactory) //.UseLazyLoadingProxies() .UseSqlServer(Conn); } optionsBuilder.UseLoggerFactory(MyLoggerFactory); } protected override void OnModelCreating(ModelBuilder modelBuilder) { #region MyRegion { //指定主键 //modelBuilder.Entity<ClassGrade>().HasKey(a => a.Id); /////设置数据库架构 //modelBuilder.HasDefaultSchema("xl"); /////表名、属性名映射 //modelBuilder.Entity<UserInfo>().ToTable("UserInfos", "Zhaoxi").Property(p => p.UserAge).HasColumnName("Age"); ////设置联合主键 //modelBuilder.Entity<SysUserRoleMapping>().HasKey(p => new { p.SysUserId, p.SysRoleId }); ////初始化数据 //modelBuilder.Entity<Company>().HasData(new List<Company>() //{ //}); ///////表拆分:在数据库中是一整张表，在代码层面是多个实体与其对应； //modelBuilder.Entity<SysLog>(dob => //{ // dob.ToTable("SysLogInfo"); // dob.Property(o => o.LogType).HasColumnName("LogType");//配置两个实体的相同属性映射到表的同一列 // dob.HasOne(o => o.SysLogDetail).WithOne().HasForeignKey<SysLog>(o => o.Id); ; //配置两个实体的相同属性映射到表的同一列 //}); //modelBuilder.Entity<SysLogDetail>(dob => //{ // dob.ToTable("SysLogInfo"); // dob.Property(o => o.LogType).HasColumnName("LogType");//配置两个实体的相同属性映射到表的同一列 //}); } //设置一对多的关系 modelBuilder.Entity<Student>().HasOne(c => c.Class).WithMany(s => s.Students).HasForeignKey(b => b.ClassId); ////多对多关系 modelBuilder.Entity<MiddleStudentCourse>(eb => { eb.HasOne(p => p.Course).WithMany(u => u.Students).HasForeignKey(u => u.CourseId); eb.HasOne(p => p.Student).WithMany(r => r.Courses).HasForeignKey(s => s.StudentId); }); modelBuilder.Entity<MiddleClassCourse>(eb => { eb.HasOne(p => p.Course).WithMany(u => u.ClassStudents).HasForeignKey(u => u.CourseId); eb.HasOne(p => p.Class).WithMany(r => r.Classs).HasForeignKey(s => s.ClassId); }); #endregion } public DbSet<ClassGrade> Classs { get; set; } public DbSet<Student> Students { get; set; } public DbSet<Course> Courses { get; set; } }2.FreeSql的流程相对EF就简单许多了，不需要执行“Add-Migration”、“Update-Database”命令，运行时检查没有表自动创建，下面是FreeSql的DbContext类，与EF很相似。
public class FreeSqlContext: DbContext { public DbSet<Student> Students { get; set; } public DbSet<Course> Courses { get; set; } public DbSet<ClassGrade> ClassGrades { get; set; } public DbSet<MiddleClassCourse> MiddleClassCourses { get; set; } public DbSet<MiddleStudentCourse> MiddleStudentCourses { get; set; } //每个 DbContext 只触发一次 protected override void OnModelCreating(ICodeFirst codefirst) { codefirst.Entity<Student>(eb => { eb.HasOne(a => a.Class).HasForeignKey(b => b.ClassId).WithMany(c => c.Students); }); codefirst.Entity<MiddleStudentCourse>(eb => { eb.HasOne(a => a.Student).WithMany(t => t.Courses).HasForeignKey(b => b.StudentId); eb.HasOne(a => a.Course).WithMany(t => t.Students).HasForeignKey(a => a.CourseId); }); codefirst.Entity<MiddleClassCourse>(eb => { eb.HasOne(a => a.Course).WithMany(t => t.ClassStudents).HasForeignKey(a => a.CourseId); eb.HasOne(a => a.Class).WithMany(t => t.Students).HasForeignKey(a => a.ClassId); }); } }3.SqlSuger就更简单了，不需要配置DbContext，配置如下泛型类就可以了，T为实体类
public class SqlSugerContext<T>: SimpleClient<T> where T : class, new() { public SqlSugerContext(SqlSugarClient context) : base(context)//注意这里要有默认值等于null { context.CodeFirst.SetStringDefaultLength(200).InitTables(typeof(T));//这样一个表就能成功创建了 } } public class ClassGradeService: SqlSugerContext<ClassGrade> { public ClassGradeService(SqlSugarClient context):base(context) { } } public class CourseService: SqlSugerContext<Course> { public CourseService(SqlSugarClient context) : base(context) { } } public class StudentService: SqlSugerContext<Student> { public StudentService(SqlSugarClient context) : base(context) { } } public class MiddleClassCourseCervice : SqlSugerContext<MiddleClassCourse> { public MiddleClassCourseCervice(SqlSugarClient context) : base(context) { } } public class MiddleStudentCourseService : SqlSugerContext<MiddleStudentCourse> { public MiddleStudentCourseService(SqlSugarClient context) : base(context) { } }三：配置声明 1.连接字符串（都实现了读写分离，由于只是测试，数据库主从都是同一个库，实际上不能这样写，不然没有读写分离的意义）：
"EfConnectionStrings": { "WriteConnection": "Server=localhost;Database=DbEfCore;Trusted_Connection=True;", "ReadConnectionList": [ "Server=localhost;Database=DbEfCore;Trusted_Connection=True;" ] }, "FreeSqlConnectionStrings": "Server=localhost;Database=DbFreeSql;Trusted_Connection=True;", "SqlSugerConnectionStrings": "Server=localhost;Database=DbSqlSuger;Trusted_Connection=True;"2.EF实现读写分离需要自行封装，另外两个只需要配置好连接字符就好了，下面是EF数据库读写分离的实现：
public enum WriteAndReadEnum { Write, //主库操作 Read //从库操作 }3.在ConfigureServices类中注入：
public interface IDbContextFactory { public EfDbContext ConnWriteOrRead(WriteAndReadEnum writeAndRead); }
public class DBConnectionOption { public string WriteConnection { get; set; } public List<string> ReadConnectionList { get; set; } }
public class DbContextFactory : IDbContextFactory { private readonly EfDbContext _Context = new EfDbContext(); private static int _iSeed = 0; private readonly DBConnectionOption _readAndWrite = null; public DbContextFactory(IOptionsMonitor<DBConnectionOption> options) { _readAndWrite = options.CurrentValue; } public EfDbContext ConnWriteOrRead(WriteAndReadEnum writeAndRead) { //判断枚举，不同的枚举可以创建不同的Context 或者更换Context链接； switch (writeAndRead) { case WriteAndReadEnum.Write: ToWrite(); break; //选择链接//更换_Context链接 //选择链接 case WriteAndReadEnum.Read: ToRead(); break; //选择链接//更换_Context链接 default: break; } return _Context; } /// <summary> /// 更换成主库连接 /// </summary> /// <returns></returns> private void ToWrite() { string conn = _readAndWrite.WriteConnection; _Context.ToWriteOrRead(conn); } /// <summary> /// 更换成主库连接 /// /// ///策略---数据库查询的负载均衡 /// </summary> /// <returns></returns> private void ToRead() { var conn = this._readAndWrite.ReadConnectionList[_iSeed++ % this._readAndWrite.ReadConnectionList.Count];//轮询; _Context.ToWriteOrRead(conn); } }
#region FreeSql//DbFreeSql var freestr = Configuration.GetSection("FreeSqlConnectionStrings").Value; IFreeSql fsql = new FreeSql.FreeSqlBuilder() .UseConnectionString(FreeSql.DataType.SqlServer, freestr) .UseSlave(freestr)//使用从数据库，支持多个 .UseAutoSyncStructure(true) //自动同步实体结构到数据库 .Build(); //请务必定义成 Singleton 单例模式 services.AddSingleton<IFreeSql>(fsql); services.AddFreeDbContext<FreeSqlContext>(options => options.UseFreeSql(fsql)); #endregion #region SqlSuger//DbSqlSuger var sugerstr = Configuration.GetSection("SqlSugerConnectionStrings").Value; services.AddScoped(options => new SqlSugarClient(new ConnectionConfig() { ConnectionString = sugerstr,//连接符字串 DbType = DbType.SqlServer, IsAutoCloseConnection = true, InitKeyType = InitKeyType.Attribute,//从特性读取主键自增信息 SlaveConnectionConfigs = new List<SlaveConnectionConfig>() {//使用从数据库，支持多个 new SlaveConnectionConfig() { HitRate=10, ConnectionString=sugerstr } } })); services.AddScoped<ClassGradeService>(); services.AddScoped<CourseService>(); services.AddScoped<StudentService>(); services.AddScoped<MiddleStudentCourseService>(); services.AddScoped<MiddleClassCourseCervice>(); #endregion #region EfCore//DbEfCore services.AddDbContext<EfDbContext>(options => options.UseSqlServer("name=EfConnectionStrings:WriteConnection")); services.Configure<DBConnectionOption>(Configuration.GetSection("EfConnectionStrings"));//注入多个链接 services.AddTransient<IDbContextFactory, DbContextFactory>(); #endregion四：总结 到此基本框架就搭建好了，下一篇将分别实现相同功能的三套API进行具体比较。 就目前来说，EF Core 最复杂学习成本高，同时Code First功能也是最强的，SqlSuger最简单容易上手，但是没有严格意义上的Code First，只是能够创建表而已。
.Net 常用ORM框架对比：EF Core、FreeSql、SqlSuger
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