.NET EF Core(Entity Framework Core)是微軟開發的一款開源的對象關系映射(ORM)框架,用于在.NET 應用程序中與數據庫進行交互。以下是一些.NET EF Core 的基礎知識:
1. 什么是 EF Core
EF Core 是.NET 平臺下的一個數據訪問技術,它允許開發者使用.NET 對象來表示數據庫中的數據,并通過對象的操作來實現對數據庫的增刪改查等操作,無需編寫大量的 SQL 語句。
2. 核心概念
- DbContext:是 EF Core 中的核心類,它表示與數據庫的會話,用于管理實體對象的生命周期、跟蹤對象的變化以及與數據庫進行交互。例如,通過
DbContext
可以查詢數據庫中的數據、將新對象插入到數據庫、更新或刪除現有對象等。 - 實體類:是用于表示數據庫表中數據的.NET 類。每個實體類的實例對應數據庫表中的一行數據,實體類的屬性對應表中的列。例如,可以創建一個
User
實體類來表示數據庫中的User
表,其中User
類的Id
屬性對應User
表中的Id
列。 - DbSet:是
DbContext
中的屬性,用于表示數據庫中的表。它提供了對實體類集合的操作,例如查詢、添加、刪除實體等。例如,在DbContext
中定義DbSet<User>
,就可以通過它來操作User
實體對應的數據庫表。
3. 安裝與配置
- 安裝:可以通過 NuGet 包管理器安裝 EF Core 相關的包。例如,要使用 SQL Server 數據庫,需要安裝
Microsoft.EntityFrameworkCore.SqlServer
包。 - 配置:在
Startup.cs
文件的ConfigureServices
方法中,需要配置DbContext
。例如,對于 SQL Server 數據庫,可以使用以下代碼配置:
csharp
services.AddDbContext<ApplicationDbContext>(options =>options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));
這里ApplicationDbContext
是自定義的DbContext
類,DefaultConnection
是在配置文件中定義的數據庫連接字符串。
4. 數據遷移
EF Core 的數據遷移功能允許開發者在不丟失數據的情況下對數據庫架構進行更改。例如,當實體類的屬性發生變化時,可以通過數據遷移來更新數據庫表的結構。可以使用命令行工具dotnet ef migrations add <MigrationName>
來添加一個新的遷移,然后使用dotnet ef database update
來將遷移應用到數據庫。
5. 查詢數據
可以使用DbSet
的Query
方法來查詢數據。例如,要查詢所有的User
實體,可以使用以下代碼:
csharp
using (var context = new ApplicationDbContext())
{var users = context.Users.ToList();
}
還可以使用 LINQ 語句對查詢進行過濾、排序等操作。例如,查詢年齡大于 18 歲的用戶:
csharp
using (var context = new ApplicationDbContext())
{var users = context.Users.Where(u => u.Age > 18).ToList();
}
6. 插入、更新和刪除數據
- 插入數據:創建一個實體類的實例,然后使用
DbSet
的Add
方法將其添加到DbContext
中,最后調用SaveChanges
方法將數據保存到數據庫。例如:
csharp
using (var context = new ApplicationDbContext())
{var user = new User { Name = "John Doe", Age = 25 };context.Users.Add(user);context.SaveChanges();
}
- 更新數據:先從數據庫中獲取要更新的實體對象,然后修改其屬性值,最后調用
SaveChanges
方法保存更改。例如:
csharp
using (var context = new ApplicationDbContext())
{var user = context.Users.FirstOrDefault(u => u.Id == 1);if (user!= null){user.Name = "Jane Doe";context.SaveChanges();}
}
- 刪除數據:從數據庫中獲取要刪除的實體對象,然后使用
DbSet
的Remove
方法將其從DbContext
中移除,最后調用SaveChanges
方法。例如:
csharp
using (var context = new ApplicationDbContext())
{var user = context.Users.FirstOrDefault(u => u.Id == 1);if (user!= null){context.Users.Remove(user);context.SaveChanges();}
}
7. 關系映射
EF Core 支持實體之間的關系映射,如一對一、一對多、多對多關系。例如,一個User
可以有多個Order
,這是一對多關系。可以通過在實體類中定義導航屬性來表示這種關系。例如,在User
類中定義ICollection<Order>
類型的屬性來表示用戶的訂單集合,在Order
類中定義User
類型的屬性來表示訂單所屬的用戶。
8.基礎操作類
9.通用EF的Service類和IService
using IService;
using System;
using System.Collections.Generic;
using System.Data.SqlClient;
using System.Linq;
using System.Linq.Expressions;
using System.Text;
using System.Threading.Tasks;namespace IService
{public interface IBaseService{#region--偽代碼//public void Add();//public void Delete();//public void Update();//public void Query();#endregion#region Query/// <summary>/// 主鍵查詢/// </summary>/// <typeparam name="T"></typeparam>/// <param name="id"></param>/// <returns></returns>public T Find<T>(int id) where T : class;/// <summary>/// 不應該暴露給上端使用者,盡量少用/// </summary>/// <typeparam name="T"></typeparam>/// <returns></returns>//[Obsolete("盡量避免使用,using 帶表達式目錄樹的代替")]public IQueryable<T> Set<T>() where T : class;/// <summary>/// 這才是合理的做法,上端給條件,這里查詢/// </summary>/// <typeparam name="T"></typeparam>/// <param name="funcWhere"></param>/// <returns></returns>public IQueryable<T> Query<T>(Expression<Func<T, bool>> funcWhere) where T : class;/// <summary>/// 分頁查詢/// </summary>/// <typeparam name="T"></typeparam>/// <typeparam name="S"></typeparam>/// <param name="funcWhere"></param>/// <param name="pageSize"></param>/// <param name="pageIndex"></param>/// <param name="funcOrderby"></param>/// <param name="isAsc"></param>/// <returns></returns>public PagingData<T> QueryPage<T, S>(Expression<Func<T, bool>> funcWhere, int pageSize, int pageIndex, Expression<Func<T, S>> funcOrderby, bool isAsc = true) where T : class;#endregion#region Insert/// <summary>/// 即使保存 不需要再Commit/// </summary>/// <typeparam name="T"></typeparam>/// <param name="t"></param>/// <returns></returns>public T Insert<T>(T t) where T : class;/// <summary>/// 新增集合/// </summary>/// <typeparam name="T"></typeparam>/// <param name="tList"></param>/// <returns></returns>public IEnumerable<T> Insert<T>(IEnumerable<T> tList) where T : class;#endregion#region Update/// <summary>/// 是沒有實現查詢,直接更新的,需要Attach和State/// /// 如果是已經在context,只能再封裝一個(在具體的service)/// </summary>/// <typeparam name="T"></typeparam>/// <param name="t"></param>public void Update<T>(T t) where T : class;/// <summary>/// 修改一個集合/// </summary>/// <typeparam name="T"></typeparam>/// <param name="tList"></param>public void Update<T>(IEnumerable<T> tList) where T : class;#endregion#region Delete/// <summary>/// 先附加 再刪除/// </summary>/// <typeparam name="T"></typeparam>/// <param name="t"></param>public void Delete<T>(T t) where T : class;/// <summary>/// 還可以增加非即時commit版本的,/// 做成protected/// </summary>/// <typeparam name="T"></typeparam>/// <param name="Id"></param>public void Delete<T>(int Id) where T : class;public void Delete<T>(IEnumerable<T> tList) where T : class;#endregion#region Other/// <summary>/// 執行Sql語句,返回IQueryable/// </summary>/// <typeparam name="T"></typeparam>/// <param name="sql"></param>/// <param name="parameters"></param>/// <returns></returns>public IQueryable<T> ExcuteQuery<T>(string sql, SqlParameter[] parameters) where T : class;/// <summary>/// 執行Sql語句,返回實體對象/// </summary>/// <typeparam name="T"></typeparam>/// <param name="sql"></param>/// <param name="parameters"></param>public void Excute<T>(string sql, SqlParameter[] parameters) where T : class;#endregionList<T> FindEntitiesByProperty<T, TProperty>(System.Linq.Expressions.Expression<System.Func<T, TProperty>> propertySelector, TProperty value) where T : class;}
}----------------------------------------------------------------------------------
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Storage;
using System;
using System.Collections.Generic;
using System.Data.SqlClient;
using System.Linq;
using System.Linq.Expressions;
using System.Text;
using System.Threading.Tasks;
using IService;namespace Service
{public abstract class BaseService : IBaseService{#region--偽代碼//public void Add()//{// throw new NotImplementedException();//}//public void Delete()//{// throw new NotImplementedException();//}//public void Query()//{// throw new NotImplementedException();//}//public void Update()//{// throw new NotImplementedException();//}#endregionprotected DbContext Context { get; set; }/// <summary>/// 構造函數注入/// </summary>/// <param name="context"></param>public BaseService(DbContext context){Context = context;}#region Query/// <summary>/// 主鍵查詢/// </summary>/// <typeparam name="T"></typeparam>/// <param name="id"></param>/// <returns></returns>public T Find<T>(int id) where T : class{return this.Context.Set<T>().Find(id);}/// <summary>/// 不應該暴露給上端使用者,盡量少用/// </summary>/// <typeparam name="T"></typeparam>/// <returns></returns>//[Obsolete("盡量避免使用,using 帶表達式目錄樹的代替")]public IQueryable<T> Set<T>() where T : class{return this.Context.Set<T>();}/// <summary>/// 這才是合理的做法,上端給條件,這里查詢/// </summary>/// <typeparam name="T"></typeparam>/// <param name="funcWhere"></param>/// <returns></returns>public IQueryable<T> Query<T>(Expression<Func<T, bool>> funcWhere) where T : class{return this.Context.Set<T>().Where<T>(funcWhere);}/// <summary>/// 分頁查詢/// </summary>/// <typeparam name="T"></typeparam>/// <typeparam name="S"></typeparam>/// <param name="funcWhere"></param>/// <param name="pageSize"></param>/// <param name="pageIndex"></param>/// <param name="funcOrderby"></param>/// <param name="isAsc"></param>/// <returns></returns>public PagingData<T> QueryPage<T, S>(Expression<Func<T, bool>> funcWhere, int pageSize, int pageIndex, Expression<Func<T, S>> funcOrderby, bool isAsc = true) where T : class{var list = Set<T>();if (funcWhere != null){list = list.Where<T>(funcWhere);}if (isAsc){list = list.OrderBy(funcOrderby);}else{list = list.OrderByDescending(funcOrderby);}PagingData<T> result = new PagingData<T>(){DataList = list.Skip((pageIndex - 1) * pageSize).Take(pageSize).ToList(),PageIndex = pageIndex,PageSize = pageSize,RecordCount = list.Count()};return result;}#endregion#region Insert/// <summary>/// 即使保存 不需要再Commit/// </summary>/// <typeparam name="T"></typeparam>/// <param name="t"></param>/// <returns></returns>public T Insert<T>(T t) where T : class{this.Context.Set<T>().Add(t);this.Commit();//寫在這里 就不需要單獨commit 不寫就需要return t;}public IEnumerable<T> Insert<T>(IEnumerable<T> tList) where T : class{this.Context.Set<T>().AddRange(tList);this.Commit();//一個鏈接 多個sqlreturn tList;}#endregion#region Update/// <summary>/// 是沒有實現查詢,直接更新的,需要Attach和State/// /// 如果是已經在context,只能再封裝一個(在具體的service)/// </summary>/// <typeparam name="T"></typeparam>/// <param name="t"></param>public void Update<T>(T t) where T : class{if (t == null) throw new Exception("t is null");this.Context.Set<T>().Attach(t);//將數據附加到上下文,支持實體修改和新實體,重置為UnChangedthis.Context.Entry<T>(t).State = EntityState.Modified;this.Commit();//保存 然后重置為UnChanged}public void Update<T>(IEnumerable<T> tList) where T : class{foreach (var t in tList){this.Context.Set<T>().Attach(t);this.Context.Entry<T>(t).State = EntityState.Modified;}this.Commit();}#endregion#region Delete/// <summary>/// 先附加 再刪除/// </summary>/// <typeparam name="T"></typeparam>/// <param name="t"></param>public void Delete<T>(T t) where T : class{if (t == null) throw new Exception("t is null");this.Context.Set<T>().Attach(t);this.Context.Set<T>().Remove(t);this.Commit();}/// <summary>/// 還可以增加非即時commit版本的,/// 做成protected/// </summary>/// <typeparam name="T"></typeparam>/// <param name="Id"></param>public void Delete<T>(int Id) where T : class{T t = this.Find<T>(Id);//也可以附加if (t == null) throw new Exception("t is null");this.Context.Set<T>().Remove(t);this.Commit();}public void Delete<T>(IEnumerable<T> tList) where T : class{foreach (var t in tList){this.Context.Set<T>().Attach(t);}this.Context.Set<T>().RemoveRange(tList);this.Commit();}#endregion#region Otherpublic void Commit(){Context.SaveChanges(); //EFCore中對于增刪改 ,必須要執行這句話才能生效}/// <summary>/// 執行Sql語句,返回IQueryable/// </summary>/// <typeparam name="T"></typeparam>/// <param name="sql"></param>/// <param name="parameters"></param>/// <returns></returns>public IQueryable<T> ExcuteQuery<T>(string sql, SqlParameter[] parameters) where T : class{return this.Context.Set<T>().FromSqlRaw(sql, parameters);}/// <summary>/// 執行Sql語句,返回實體對象/// </summary>/// <typeparam name="T"></typeparam>/// <param name="sql"></param>/// <param name="parameters"></param>public void Excute<T>(string sql, SqlParameter[] parameters) where T : class{IDbContextTransaction trans = null;try{trans = Context.Database.BeginTransaction();this.Context.Database.ExecuteSqlRaw(sql, parameters);trans.Commit();}catch (Exception){if (trans != null)trans.Rollback();throw;}}/// <summary>/// 釋放回收/// </summary>public virtual void Dispose(){if (Context != null){Context.Dispose();}}#endregionpublic List<T> FindEntitiesByProperty<T, TProperty>(Expression<Func<T, TProperty>> propertySelector, TProperty value) where T : class{var propertyValueEqualExpression = Expression.Equal(propertySelector.Body, Expression.Constant(value));var lambda = Expression.Lambda<Func<T, bool>>(propertyValueEqualExpression, propertySelector.Parameters);return Context.Set<T>().Where(lambda).ToList();}}
}
10.創建表的案例
using DbModels;
using static System.Runtime.InteropServices.JavaScript.JSType;namespace Initial_EFDB
{internal class Program{static void Main(string[] args){string connectionString = "Data Source=WIN-20240630YNV\\SQLEXPRESS;" +"Initial Catalog= EFCoreTestDB;Persist Security Info=True;User ID=sa;" +"Password=lyh2016;Encrypt=True;Trust Server Certificate=True";Console.WriteLine("Hello, World!");using (AgiletyDbContext context = new AgiletyDbContext(connectionString)){//根據數據庫連接字符串的配置刪除數據庫,如果不存在就不操作context.Database.EnsureDeleted();//根據數據庫連接字符串的配置創建數據庫,如果存在就不創建 context.Database.EnsureCreated();var adduser = new DbModels.Models.UserEntity(){Address = "武漢市",Email = "18672554858@163.com",Imageurl = "",LastLoginTime = DateTime.Now,Mobile = "18672554858",Name = "Ricahrd",Password = "123456",QQ = "8542313245",Phone = "15845858858",Sex = 1,UserType = 1,WeChat = ""};context.UserEntities.Add(adduser);context.SaveChanges();查詢//UserEntity user = context.UserEntities.OrderByDescending(c => c.UserId).FirstOrDefault();//user.Name = "Richard 老師";//context.SaveChanges();//context.Remove(user);//context.SaveChanges();}}}
}
11.數據操作案例UserService和IUserService
using ModelDto;namespace IService
{public interface IUserService: IBaseService{/// <summary>/// 登錄功能/// </summary>/// <param name="userName"></param>/// <param name="password"></param>/// <returns></returns>public UserDto? Login(string userName, string password);public void ShowUserAndCompany();public void SetUserAndCompany();}
}-----------------------------------------------------------------------using AutoMapper;
using Microsoft.EntityFrameworkCore;
using DbModels.Models;
using IService;
using ModelDto;
using Service;namespace Zhaoxi.AgiletyFramework.BusinessServices
{public class UserService : BaseService, IUserService{private readonly IMapper _IMapper;public UserService(DbContext context, IMapper iMapper) : base(context){_IMapper = iMapper;}/// <summary>/// 登錄功能/// </summary>/// <param name="userName"></param>/// <param name="password"></param>/// <returns></returns>public UserDto? Login(string userName, string password){string pwd = password;// MD5Encrypt.Encrypt(password);List<UserEntity> userList = Context.Set<UserEntity>().Where(c => c.Name.Equals(userName) && c.Password.Equals(pwd)).ToList();if (userList == null || userList.Count <= 0){return null;}UserEntity user = userList.First();UserDto userDto = _IMapper.Map<UserEntity, UserDto>(user);List<int> roleIdList = Context.Set<UserRoleMapEntity>().Where(c => c.UserId == user.UserId).Select(r => r.RoleId).ToList();userDto.RoleIdList = roleIdList;//設置登錄用戶角色//登錄用戶的菜單idList<Guid> userMenuIds = Context.Set<RoleMenuMapEntity>().Where(c => roleIdList.Contains(c.Id)).Select(c => c.MenuId).ToList();return userDto;}/// <summary>/// Autofac支持額aop擴展,如果通過類的方式來支持Aop,只有定義成Virtual方法,才能夠進入到aop內部去;/// </summary>public virtual void SetUserAndCompany(){}public void ShowUserAndCompany(){ }}
}
12.控制器的應用案例
using AutoMapper;
using DbModels.Models;
using EFTest.Comm;
using IService;
using Microsoft.AspNetCore.Mvc;
using ModelDto;
using Service;namespace EFTest.Controllers
{/// <summary>/// Api控制器,用戶相關的API/// </summary>[Route("api/[controller]/[action]")] // 修改路由前綴,包含控制器名稱和方法名稱[ApiController]public class UserController : ControllerBase{private readonly IUserService _IUserService;private readonly IMapper _IMapper; //AutoMapper映射使用/// <summary>/// 構造函數/// </summary>/// <param name="iUserService"></param>/// <param name="iMapper"></param>public UserController( IUserService iUserService, IMapper iMapper){_IUserService = iUserService;_IMapper = iMapper;}/// <summary>/// 獲取用戶的分頁列表/// </summary>/// <param name="pageindex"></param>/// <param name="pageSize"></param>/// <param name="searchaString"></param>/// <returns></returns>[HttpGet][Route("{pageindex:int}/{pageSize:int}")][Route("{pageindex:int}/{pageSize:int}/{searchaString}")]public async Task<JsonResult> GetUserPageAsync(int pageindex, int pageSize, string? searchaString = null){PagingData<UserEntity> paging = _IUserService.QueryPage<UserEntity, DateTime>(!string.IsNullOrWhiteSpace(searchaString) ? c => c.Name.Contains(searchaString) : a => true, pageSize, pageindex, c => c.CreateTime, false);PagingData<UserDto> pagingResult = _IMapper.Map<PagingData<UserEntity>, PagingData<UserDto>>(paging);JsonResult result = new JsonResult(new ApiDataResult<PagingData<UserDto>>(){Data = pagingResult,Success = true,Message = "用戶分頁列表"});return await Task.FromResult(result);}/// <summary>/// 新增用戶/// </summary>/// <param name="userDto"></param>/// <returns></returns>[HttpPost]public async Task<JsonResult> AddUserAsync([FromBody] AddUserDto userDto){UserEntity adduser = _IMapper.Map<AddUserDto, UserEntity>(userDto);UserEntity user = _IUserService.Insert(adduser);var result = new JsonResult(new ApiDataResult<UserEntity>() { Data = adduser, Success = true, Message = "添加用戶" });if (user.UserId <= 0){result = new JsonResult(new ApiDataResult<UserEntity>() { Data = adduser, Success = false, Message = "添加用戶失敗" });}return await Task.FromResult(result);}/// <summary>/// 根據名稱查詢用戶列表/// </summary>/// <param name="name">要查詢的用戶名</param>/// <returns>符合條件的用戶列表</returns>[HttpGet]public IActionResult SelectByName(string name){if (string.IsNullOrEmpty(name)){return BadRequest("用戶名不能為空");}var userList = _IUserService.FindEntitiesByProperty<UserEntity, string>(u => u.Name, name);return Ok(userList);}/// <summary>/// 基于 name 對 User 模型進行數據更新/// <param name="updatedUser">更新后的用戶數據</param>/// <returns>返回更新結果信息</returns>[HttpPost]public async Task<IActionResult> UpdateUserByName(UserEntity updatedUser){try{// 根據 name 查詢用戶列表var usersToUpdate = _IUserService.FindEntitiesByProperty<UserEntity, string>(u => u.Name ,updatedUser.Name);if (usersToUpdate == null || usersToUpdate.Count == 0){return NotFound($"沒有找到名為 {updatedUser.Name} 的用戶");}// 更新每個找到的用戶foreach (var user in usersToUpdate){// 這里簡單地將更新后的屬性值賦給原用戶對象,你可以根據實際需求進行更復雜的屬性更新邏輯//user.UserId = updatedUser.UserId;user.Sex = updatedUser.Sex;user.Address = updatedUser.Address;user.Name= updatedUser.Name;_IUserService.Update(user);}return Ok($"成功更新了名為 {updatedUser.Name} 的用戶數據");}catch (Exception ex){return StatusCode(500, $"更新用戶數據時發生錯誤: {ex.Message}");}}/// <summary>/// 基于 name 對 User 模型進行數據刪除/// </summary>/// <param name="name">要刪除的用戶的 name</param>/// <returns>返回刪除結果信息</returns>[HttpDelete("{name}")]public async Task<IActionResult> DeleteUserByName(string name){try{// 根據 name 查詢用戶列表var usersToDelete = _IUserService.FindEntitiesByProperty<UserEntity, string>(u => u.Name, name);if (usersToDelete == null || usersToDelete.Count == 0){return NotFound($"沒有找到名為 {name} 的用戶");}// 刪除每個找到的用戶_IUserService.Delete<UserEntity>(usersToDelete);return Ok($"成功刪除了名為 {name} 的用戶數據");}catch (Exception ex){return StatusCode(500, $"刪除用戶數據時發生錯誤: {ex.Message}");}}/// <summary>/// 查詢 user 表所有數據/// </summary>/// <returns>返回 user 表的所有數據</returns>[HttpGet]public async Task<IActionResult> GetAllUsers(){try{// 調用 IBaseService 的 Query 方法查詢所有 User 數據var users = _IUserService.Query<UserEntity>(u => true).ToList();return Ok(users);}catch (Exception ex){return StatusCode(500, $"查詢用戶數據時發生錯誤: {ex.Message}");}}}
}