EF6中可以直接根據代碼模型生成數據庫Database.SetInitializer即可
在EFCore中如何實現呢？
這項功能放在了DatabaseFacade對象中，傳入數據庫上下文對象實例化到一個DatabaseFacade對象
可以看到DatabaseFacade有幾個方法：
獲取所有遷移的migraion數據：GetMigrations
獲取待遷移的migration數據 ：GetPendingMigrations
獲取已經操作的migration數據：GetAppliedMigrations
適配migration： Migrate
這中間有一個坑：efcore 貌似還不能根據模型生成數據庫，而是要先添加migrations的文件，然后才能適配數據庫
這里我添加了一個XXXX字段，按照正常的流程：我們需要執行命令：
dotnet ef migrations add addxxxxxx
dotnet ef database update
EFCore中的自動適配數據庫的前提是添加好 新增變量的migrations文件，實際上只是efcore只幫助了我們實現了dotnet ef database update的操作
首先先操作下：dotnet ef migrations add addxxxxxx
這里我寫了一個簡單的中間件來說明下：
通過注冊服務，添加usermap引用
/// <summary> /// liyouming add 20180508 /// </summary> /// <typeparam name="T">（context）上下文對象</typeparam> /// <param name="service">擴展服務</param> /// <param name="optionsAction">配置</param> /// <returns></returns> public static IServiceCollection AddEFMigrations<T>(this IServiceCollection service, Action<DbContextOptionsBuilder> optionsAction) where T : DbContext { service.AddDbContext<T>(optionsAction); var serviceProvider = service.BuildServiceProvider(); service.AddSingleton<IEFMigrationsContext>(new EFMigrationsContext(serviceProvider.GetRequiredService(typeof(T)) as DbContext)); return service; }
這里我們需要指導上下文對象T，並將該對象放到自定義的服務 IEFMigrationsContext 去處理下
然后擴展下IApplicationBuilder
public static IApplicationBuilder UseEFMigraions( this IApplicationBuilder builder,string pathstring) { builder.Map(new Microsoft.AspNetCore.Http.PathString(pathstring), app => { app.UseMiddleware<EFMigrationsMiddleware>(pathstring); }); return builder; }
比較簡單，需要map下地址，當我們訪問的時候進入到固定頁面操作
public class EFMigrationsMiddleware { private readonly RequestDelegate _next; private readonly string _pathstring; private IEFMigrationsContext _migrationsContext; public EFMigrationsMiddleware(RequestDelegate next, string pathstring, IEFMigrationsContext migrationsContext) { if (next == null) { throw new Exception(nameof(next)); } _next = next; _pathstring = pathstring; _migrationsContext = migrationsContext; } public async Task Invoke(HttpContext context) { if (context.Request.PathBase == _pathstring) { var list = _migrationsContext.GetPendingMigrations(); _migrationsContext.AutoMigration(); string strli = string.Empty; foreach (var item in list) { strli += "<li>" + item + "</li>"; } await context.Response.WriteAsync("<html><body><ul>" + strli + "</ul></body></html>"); } else { await _next(context); } return; } }
下面直接實現接口方法就ok了,存在待更新的migrations就執行更新
public void AutoMigration() { if (databaseFacade.GetPendingMigrations().Any()) { //執行遷移 databaseFacade.Migrate(); } }
下面來說下使用方式：跟原有的dbcontext使用方式一樣，配置好你的上下文對象配置
注冊服務：
services.AddEFMigrations<UserDbContext>(optionsBuilder => { var _userappsetting = Configuration.Get<UserAppSetting>(); if (_userappsetting == null) { throw new Exception("數據庫連接字符串未配置"); } switch (_userappsetting.DbType) { case 1: optionsBuilder.UseSqlServer(_userappsetting.UserConnectionString, sqlserver => { sqlserver.MigrationsAssembly(_migrationAssablyName); sqlserver.UseRelationalNulls(); sqlserver.UseRowNumberForPaging(); }); break; case 2: optionsBuilder.UseMySQL(_userappsetting.UserConnectionString, mysql => { mysql.MigrationsAssembly(_migrationAssablyName); mysql.UseRelationalNulls(); }); break; default: optionsBuilder.UseSqlServer(_userappsetting.UserConnectionString, sqlserver => { sqlserver.MigrationsAssembly(_migrationAssablyName); sqlserver.UseRelationalNulls(); sqlserver.UseRowNumberForPaging(); }); break; } });
添加Configure
app.UseEFMigraions("/Migrations");
下面訪問下：/Migrations ，這里上面的代碼中我先獲取了待更新的migraions 方便驗證，這里可以看到待驗證的migraions是我新添加 addxxxxxxx
下面我們來檢查數據生成情況：
已經生成了 XXXXX字段
如果能不操作dotnet ef migrations add addxxxxxx就好了，感覺還是有點雞肋~~~