网上有好多解释，有些上升到了架构设计，让你觉得似乎非常高深莫测，特别是目前流行的ABP架构中就有提到多租户（IMustHaveTenant），其实说的简单一点就是再每一张数据库的表中添加一个TenantId的字段，用于区分属于不同的租户（或是说不同的用户组）的数据。关键是现实的方式必须对开发人员来说是透明的，不需要关注这个字段的信息，由后台或是封装在基类中实现数据的筛选和更新。
基本原理
从新用户注册时就必须指定用户的TenantId,我的例子是用CompanyId,公司信息做为TenantId,哪些用户属于不同的公司，每个用户将来只能修改和查询属于本公司的数据。
接下来就是用户登录的时候获取用户信息的时候把TenantId保存起来，asp.net mvc（不是 core） 是通过 Identity 2.0实现的认证和授权，这里需要重写部分代码来实现。
最后用户对数据查询/修改/新增时把用户信息中TenantId，这里就需要设定一个Filter(过滤器)和每次SaveChange的插入TenantId
如何实现
第一步，扩展 Asp.net Identity user 属性，必须新增一个TenantId字段,根据Asp.net Mvc 自带的项目模板修改IdentityModels.cs 这个文件
// You can add profile data for the user by adding more properties to your ApplicationUser class, please visit ?LinkID=317594 to learn more. public class ApplicationUser : IdentityUser { public async Task<ClaimsIdentity> GenerateUserIdentityAsync(UserManager<ApplicationUser> manager, string authenticationType) { // Note the authenticationType must match the one defined in CookieAuthenticationOptions.AuthenticationType var userIdentity = await manager.CreateIdentityAsync(this, authenticationType); // Add custom user claims here userIdentity.AddClaim(new Claim("http://schemas.microsoft.com/identity/claims/tenantid", this.TenantId.ToString())); userIdentity.AddClaim(new Claim("CompanyName", this.CompanyName)); userIdentity.AddClaim(new Claim("EnabledChat", this.EnabledChat.ToString())); userIdentity.AddClaim(new Claim("FullName", this.FullName)); userIdentity.AddClaim(new Claim("AvatarsX50", this.AvatarsX50)); userIdentity.AddClaim(new Claim("AvatarsX120", this.AvatarsX120)); return userIdentity; } public async Task<ClaimsIdentity> GenerateUserIdentityAsync(UserManager<ApplicationUser> manager) { // Note the authenticationType must match the one defined in CookieAuthenticationOptions.AuthenticationType var userIdentity = await manager.CreateIdentityAsync(this, DefaultAuthenticationTypes.ApplicationCookie); // Add custom user claims here return userIdentity; } [Display(Name = "全名")] public string FullName { get; set; } [Display(Name = "性别")] public int Gender { get; set; } public int AccountType { get; set; } [Display(Name = "所属公司")] public string CompanyCode { get; set; } [Display(Name = "公司名称")] public string CompanyName { get; set; } [Display(Name = "是否在线")] public bool IsOnline { get; set; } [Display(Name = "是否开启聊天功能")] public bool EnabledChat { get; set; } [Display(Name = "小头像")] public string AvatarsX50 { get; set; } [Display(Name = "大头像")] public string AvatarsX120 { get; set; } [Display(Name = "租户ID")] public int TenantId { get; set; } } public class ApplicationDbContext : IdentityDbContext<ApplicationUser> { public ApplicationDbContext() : base("DefaultConnection", throwIfV1Schema: false) => Database.SetInitializer<ApplicationDbContext>(null); public static ApplicationDbContext Create() => new ApplicationDbContext(); }
第二步 修改注册用户的代码，注册新用户的时候需要选择所属的公司信息
[HttpPost] [AllowAnonymous] [ValidateAntiForgeryToken] public async Task<ActionResult> Register(AccountRegistrationModel viewModel) { var data = this._companyService.Queryable().Select(x => new ListItem() { Value = x.Id.ToString(), Text = x.Name }); this.ViewBag.companylist = data; // Ensure we have a valid viewModel to work with if (!this.ModelState.IsValid) { return this.View(viewModel); } // Try to create a user with the given identity try { // Prepare the identity with the provided information var user = new ApplicationUser { UserName = viewModel.Username, FullName = viewModel.Lastname + "." + viewModel.Firstname, CompanyCode = viewModel.CompanyCode, CompanyName = viewModel.CompanyName, TenantId=viewModel.TenantId, Email = viewModel.Email, AccountType = 0 }; var result = await this.UserManager.CreateAsync(user, viewModel.Password); // If the user could not be created if (!result.Succeeded) { // Add all errors to the page so they can be used to display what went wrong this.AddErrors(result); return this.View(viewModel); } // If the user was able to be created we can sign it in immediately // Note: Consider using the email verification proces await this.SignInAsync(user, true); return this.RedirectToLocal(); } catch (DbEntityValidationException ex) { // Add all errors to the page so they can be used to display what went wrong this.AddErrors(ex); return this.View(viewModel); } } AccountController.cs
第三步 读取登录用户的TenantId 在用户查询和新增修改时把TenantId插入到表中,这里需要引用
Z.EntityFramework.Plus，这个是免费开源的一个类库，功能强大