标签：except 访问 UNC 创建时间 推荐 dea manage 必须 order
每一个拥有数据库的项目，都会涉及到数据库数据的操作，而很多时候都会用到相同的方法，但是只是涉及到的表不一样，如果不对这些类似方法进行封装，开发上就会造成时间上的浪费。
那么如何对这些方法进行封装呢？
要会封装方法，最基本的得先了解 泛型 是什么，什么是泛型，博客园上有很多对这个的讲解，我也相信，科班的人对这个应该都有大概的了解，
其次得了解 反射，当然，很多人会说反射会影响性能，但是在如今设备都是很好的情况下，反射影响的性能微乎其微吧~
言归正传，说的再多不如实操，那么我们先新建数据库表的基类，并让数据库表类继承它，这样来约束泛型的类型只能是数据表对象，不能是其它类型，以此来避免不必要的错误！
/// <summary> /// 数据库基类 /// </summary> public abstract class EntityBase : IEntityBase { }
这里的 IEntityBase 是前面第二篇中用到的一个空的接口基类，在这个抽象基类中，可以添加字段，这样继承该基类的数据库表都会加上这些字段，比如 创建时间、创建人等字段
因为这里会涉及到分页模型的因素，先新建泛型的分页模型类 PageResponse
/// <summary> /// 分页模型 /// </summary> /// <typeparam name="T"></typeparam> public class PageResponse<T> { private long _recordTotal; /// <summary> /// 当前页码 /// </summary> public int PageIndex { get; set; } /// <summary> /// 总页数 /// </summary> public int PageTotal { get; set; } = 1; /// <summary> /// 每页大小 /// </summary> public int PageSize { get; set; } /// <summary> /// 总记录数 /// </summary> public long RecordTotal { get => _recordTotal; set { _recordTotal = value; if (PageSize <= 0) return; PageTotal = (int)Math.Ceiling(RecordTotal / (double)PageSize); } } public List<T> Data { get; set; } public PageResponse() { Data = new List<T>(); } public PageResponse(List<T> data, int pageIndex, int pageTotal) { Data = data; PageIndex = pageIndex; PageTotal = pageTotal; } }
接下来我们新建一个数据库工厂类 来 进行 生产数据库上下文，代码如下
/// <summary> /// 数据库工厂 /// </summary> public class DbContextFactory { /// <summary> /// 数据库上下文 /// </summary> /// <returns></returns> public static DemoDbContext GetCurrentDbContext() { if (DemoWeb.HttpContext.Items["DbContext"] is DemoDbContext dbContext) return dbContext; dbContext = DemoWeb.IocManager.Resolve<DemoDbContext>();//从容器中得到数据库上下文 放置在 Items 中， 访问结束自动销毁 //dbContext = DemoWeb.HttpContext.RequestServices.GetService(typeof(DemoDbContext)) as DemoDbContext; DemoWeb.HttpContext.Items["DbContext"] = dbContext; return dbContext; } }
因为这里使用的是autofac模式，所以这样获取。至于为什么放到items中，也有简单的原因讲到。
再然后新建 IBaseDao 接口文件，代码如下：
public interface IBaseDao<T> { T Add(T entity); List<T> Add(List<T> entity); void Delete(params object[] keyValues); void Delete(object objectId); void Delete(Expression<Func<T, bool>> whereFun); void Update(T entity); void Update(Expression<Func<T, bool>> where, Dictionary<string, object> dic); bool Exist(Expression<Func<T, bool>> anyLambda); T Find(params object[] keyValues); IQueryable<T> Where(Expression<Func<T, bool>> whereLambda); T FirstOrDefault(Expression<Func<T, bool>> whereLambda); int Count(Expression<Func<T, bool>> countLambda); T First(Expression<Func<T, bool>> firstLambda); IQueryable<T> LoadEntities(Expression<Func<T, bool>> whereLambda = null); List<T> LoadPageEntities<TKey>(int pageIndex, int pageSize, out int totalCount, out int pageCount, Expression<Func<T, bool>> whereLambda, bool isAsc, Expression<Func<T, TKey>> orderBy); PageResponse<T> LoadPageEntities<TKey>(int pageIndex, int pageSize, Expression<Func<T, bool>> whereLambda, bool isAsc, Expression<Func<T, TKey>> orderBy); IQueryable<TQ> LoadPageEntities<TQ, TKey>(IQueryable<TQ> query, int pageIndex, int pageSize, out int totalCount, out int pageCount, bool isAsc, Expression<Func<TQ, TKey>> orderBy) where TQ : class, new(); PageResponse<TQ> LoadPageEntities<TQ, TKey>(IQueryable<TQ> query, int pageIndex, int pageSize, bool isAsc, Expression<Func<TQ, TKey>> orderBy) where TQ : class, new(); int SaveChanges(); }
实现接口的类，代码如下： 代码有点长~~所以就折叠了~~
/// <summary> /// 数据库基类 /// </summary> /// <typeparam name="T"></typeparam> public class BaseDao<T> : IBaseDao<T> where T : EntityBase, new() { public DemoDbContext DbContext => DbContextFactory.GetCurrentDbContext(); public BaseDao() { //DbContext = DbContextFactory.GetCurrentDbContext(); } #region 增删改的公共方法 public T Add(T entity) { DbContext.Set<T>().Add(entity); //DbContext.Entry(entity).State = EntityState.Added; return entity; } public List<T> Add(List<T> entitys) { DbContext.Set<T>().AddRange(entitys); //注释掉下面的快许多 且不影响保存 //foreach (var model in entitys) //{ // DbContext.Entry(model).State = EntityState.Added; //} return entitys; } public void Delete(Expression<Func<T, bool>> whereFun) { IEnumerable<T> queryable = DbContext.Set<T>().Where(whereFun); //DbContext.Set<T>().RemoveRange(queryable); foreach (var model in queryable) { DbContext.Entry(model).State = EntityState.Deleted; } } public void Update(T entity) { DbContext.Entry(entity).State = EntityState.Modified; } public void Update(Expression<Func<T, bool>> @where, Dictionary<string, object> dic) { IEnumerable<T> queryable = DbContext.Set<T>().Where(@where).ToList(); Type type = typeof(T); List<PropertyInfo> propertyList = type.GetProperties(BindingFlags.Public | BindingFlags.Instance).ToList(); //遍历结果集 foreach (T entity in queryable) { foreach (var propertyInfo in propertyList) { string propertyName = propertyInfo.Name; if (dic.ContainsKey(propertyName)) { //设置值 propertyInfo.SetValue(entity, dic[propertyName], null); } } Update(entity); } } public void Delete(params object[] keyValues) { var entity = DbContext.Set<T>().Find(keyValues); DbContext.Entry(entity).State = EntityState.Deleted; } public void Delete(object objectId) { var entity = DbContext.Set<T>().Find(objectId); DbContext.Entry(entity).State = EntityState.Deleted; } #endregion #region 查询方法 /// <summary> /// 查看是否存在 /// </summary> /// <typeparam name="T"></typeparam> /// <param name="anyLambda"></param> /// <returns></returns> public bool Exist(Expression<Func<T, bool>> anyLambda) { return DbContext.Set<T>().Any(anyLambda); } /// <summary> /// 根据主键得到数据 /// </summary> /// <typeparam name="T"></typeparam> /// <param name="keyValues"></param> /// <returns></returns> public T Find(params object[] keyValues) { return DbContext.Set<T>().Find(keyValues); } /// <summary> /// 根据where条件查找 /// </summary> /// <typeparam name="T"></typeparam> /// <param name="whereLambda"></param> /// <returns></returns> public IQueryable<T> Where(Expression<Func<T, bool>> whereLambda) { return DbContext.Set<T>().Where(whereLambda); } /// <summary> /// 获取第一个或默认为空 /// </summary> /// <param name="whereLambda"></param> /// <returns></returns> public T FirstOrDefault(Expression<Func<T, bool>> whereLambda) { return DbContext.Set<T>().FirstOrDefault(whereLambda); } /// <summary> /// 得到条数 /// </summary> /// <typeparam name="T"></typeparam> /// <param name="countLambda"></param> /// <returns></returns> public int Count(Expression<Func<T, bool>> countLambda) { return DbContext.Set<T>().AsNoTracking().Count(countLambda); } /// <summary> /// 获取第一个或默认的 /// </summary> /// <typeparam name="T"></typeparam> /// <param name="firstLambda"></param> /// <returns></returns> public T First(Expression<Func<T, bool>> firstLambda) { return DbContext.Set<T>().FirstOrDefault(firstLambda); } /// <summary> /// 得到IQueryable数据 /// </summary> /// <typeparam name="T"></typeparam> /// <param name="whereLambda"></param> /// <returns></returns> public IQueryable<T> LoadEntities(Expression<Func<T, bool>> whereLambda = null) { if (whereLambda == null) { return DbContext.Set<T>().AsQueryable(); } return DbContext.Set<T>().Where(whereLambda).AsQueryable(); } /// <summary> /// 从某个表中获取分页数据 /// </summary> /// <typeparam name="T"></typeparam> /// <typeparam name="TKey"></typeparam> /// <param name="pageIndex"></param> /// <param name="pageSize"></param> /// <param name="totalCount"></param> /// <param name="pageCount"></param> /// <param name="whereLambda"></param> /// <param name="isAsc"></param> /// <param name="orderBy"></param> /// <returns></returns> public List<T> LoadPageEntities<TKey>(int pageIndex, int pageSize, out int totalCount, out int pageCount, Expression<Func<T, bool>> whereLambda, bool isAsc, Expression<Func<T, TKey>> orderBy) { var temp = DbContext.Set<T>().AsNoTracking().Where(whereLambda); //去掉.AsQueryable().AsNoTracking()，将下面改为 totalCount = temp.Count(); pageCount = (int)Math.Ceiling((double)totalCount / pageSize); if (isAsc) { return temp.OrderBy(orderBy) .Skip(pageSize * (pageIndex - 1)) .Take(pageSize).ToList(); //去掉.AsQueryable()，添加.select(t=>new Dto()).ToList() } return temp.OrderByDescending(orderBy) .Skip(pageSize * (pageIndex - 1)) .Take(pageSize).ToList(); //.select(t=>new Dto()).ToList() } /// <summary> /// 返回分页模型 /// </summary> /// <typeparam name="T"></typeparam> /// <typeparam name="TKey"></typeparam> /// <param name="pageIndex"></param> /// <param name="pageSize"></param> /// <param name="whereLambda"></param> /// <param name="isAsc"></param> /// <param name="orderBy"></param> /// <returns></returns> public PageResponse<T> LoadPageEntities<TKey>(int pageIndex, int pageSize, Expression<Func<T, bool>> whereLambda, bool isAsc, Expression<Func<T, TKey>> orderBy) { var temp = DbContext.Set<T>().AsNoTracking().Where(whereLambda); var rest = new PageResponse<T>(); rest.PageIndex = pageIndex; rest.PageSize = pageSize; rest.RecordTotal = temp.Count();//记录总条数时，自动设置了总页数 if (isAsc) { rest.Data = temp.OrderBy(orderBy) .Skip(pageSize * (pageIndex - 1)) .Take(pageSize).ToList(); } rest.Data = temp.OrderByDescending(orderBy) .Skip(pageSize * (pageIndex - 1)) .Take(pageSize).ToList(); return rest; } /// <summary> /// 将查询出来的数据 转换成IQueryable，然后进行分页 不跟踪数据状态 /// </summary> /// <typeparam name="TQ">返回类型</typeparam> /// <typeparam name="TKey">根据哪个字段排序（必须）</typeparam> /// <param name="query">数据集</param> /// <param name="pageIndex">页数</param> /// <param name="pageSize">每页条数</param> /// <param name="totalCount">总条数</param> /// <param name="pageCount">总页数</param> /// <param name="isAsc">是否倒序</param> /// <param name="orderBy">排序字段</param> /// <returns>IQueryable分页结果</returns> public IQueryable<TQ> LoadPageEntities<TQ, TKey>(IQueryable<TQ> query, int pageIndex, int pageSize, out int totalCount, out int pageCount, bool isAsc, Expression<Func<TQ, TKey>> orderBy) where TQ : class, new() { IQueryable<TQ> temp = query.AsNoTracking(); totalCount = temp.Count(); pageCount = (int)Math.Ceiling((double)totalCount / pageSize); if (isAsc) { temp = temp.OrderBy(orderBy) .Skip(pageSize * (pageIndex - 1)) .Take(pageSize).AsQueryable(); } else { temp = temp.OrderByDescending(orderBy) .Skip(pageSize * (pageIndex - 1)) .Take(pageSize).AsQueryable(); } return temp; } /// <summary> /// 将查询出来的数据 转换成IQueryable，然后进行分页 不跟踪数据状态 /// </summary> /// <typeparam name="TQ">返回类型</typeparam> /// <typeparam name="TKey">根据哪个字段排序（必须）</typeparam> /// <param name="query">数据集</param> /// <param name="pageIndex">页数</param> /// <param name="pageSize">每页条数</param> /// <param name="isAsc">是否倒序</param> /// <param name="orderBy">排序字段</param> /// <returns>PageResponse分页结果</returns> public PageResponse<TQ> LoadPageEntities<TQ, TKey>(IQueryable<TQ> query, int pageIndex, int pageSize, bool isAsc, Expression<Func<TQ, TKey>> orderBy) where TQ : class, new() { var rest = new PageResponse<TQ>(); IQueryable<TQ> temp = query.AsNoTracking(); rest.RecordTotal = temp.Count(); if (isAsc) { rest.Data = temp.OrderBy(orderBy) .Skip(pageSize * (pageIndex - 1)) .Take(pageSize).ToList(); } else { rest.Data = temp.OrderByDescending(orderBy) .Skip(pageSize * (pageIndex - 1)) .Take(pageSize).ToList(); } return rest; } #endregion /// <summary> /// 自带事务，调用此方法保存 /// </summary> public int SaveChanges() { var res = -1; try { res = DbContext.SaveChanges(); //Dispose(); } catch (DbException ex) { throw new CustomSystemException($"数据库保存失败!{ex.Message}", 999); } catch (Exception ex) { throw new CustomSystemException($"数据库保存失败!{ex.Message}", 999); } return res; } public void Dispose() { this.DbContext.Dispose(); GC.SuppressFinalize(this); } }
到这里，根据每个数据库表建对应的 Dao 类，这样一来开发效率就会明显提升，示例代码如下：
public class DemoModelDao : BaseDao<DemoModel> { private static object locker = new object(); private static DemoModelDao _demoModelDao; public static DemoModelDao Instance { get { if (_demoModelDao != null) return _demoModelDao; lock (locker) { if (_demoModelDao == null) { _demoModelDao = new DemoModelDao(); } } return _demoModelDao; } } /// <summary> /// 得到分页数据 /// </summary> /// <param name="queryDemo"></param> /// <returns></returns> public PageResponse<DemoModel> DemoPageResponse(QueryDemoDto queryDemo) { var date = LoadPageEntities(queryDemo.Page, queryDemo.PageSize, c => c.CustomerName.Contains(queryDemo.Name), false, c => c.Id); return date; } }
然后添加测试方法，添加 Biz 类，调用测试
public class DemoModelBiz { private static object locker = new object(); private static DemoModelBiz _demoModelBiz; public static DemoModelBiz Instance { get { if (_demoModelBiz != null) return _demoModelBiz; lock (locker) { if (_demoModelBiz == null) { _demoModelBiz = new DemoModelBiz(); } } return _demoModelBiz; } } public string AddDemoModel(DemoModel demoModel) { DemoModelDao.Instance.Add(demoModel); var count = DemoModelDao.Instance.SaveChanges(); return count > 0 ? "success" : "save error"; } public string AddDemoModel(List<DemoModel> demoModels) { DemoModelDao.Instance.Add(demoModels); DemoModelDao.Instance.Delete(c=>c.Id == 1); DemoModelDao.Instance.Delete(c=>c.CustomerName.StartsWith("2")); TestModelDao.Instance.Add(new TestModel() { BlogName = "NET CORE", BlogPhone = 123, BlogUseDay = 90 }); var count = DemoModelDao.Instance.SaveChanges(); return count > 0 ? "success" : "save error"; } /// <summary> /// 得到分页数据 /// </summary> /// <param name="queryDemo"></param> /// <returns></returns> public PageResponse<DemoModel> DemoModelList(QueryDemoDto queryDemo) { return DemoModelDao.Instance.DemoPageResponse(queryDemo); } }
再添加测试的控制器类，示例代码如下：
[Route("api/[controller]")] public class DemoModelController : BaseController { [Route("testadd"), HttpPost] public async Task<ActionResult> AddDemoModel() { var models = new List<DemoModel>(); for (int i = 0; i < 100; i++) { var testModel = new DemoModel() { CustomerName = i +"-Levy" + DateTime.Now.ToString("HH:mm:ss"), IdentityCardType = 1 }; models.Add(testModel); } for (int i = 0; i < 100; i++) { var testModel = new DemoModel() { CustomerName = i + "-zzzz" + DateTime.Now.ToString("HH:mm:ss"), IdentityCardType = 2 }; models.Add(testModel); } var res = await Task.FromResult(DemoModelBiz.Instance.AddDemoModel(models)); return Succeed(res); } [Route("demolist"), HttpPost] public async Task<ActionResult> DemoModelList([FromBody] QueryDemoDto queryDemo) { var res = await Task.FromResult(DemoModelBiz.Instance.DemoModelList(queryDemo)); return Succeed(res); } }
涉及到的类：
public class QueryDemoDto { public int Page { get; set; } public int PageSize { get; set; } public string Name { get; set; } }
接下来就运行程序调试看结果吧~
这里数据保存成功之后我们进行数据的查询，
可以看到查询出结果，这里有两千多条数据，是因为执行了多次且每次保存前都会删除以2开始的数据。
题外话，因为我们是将数据库上下文放在 HttpContext.Items 中的，可能有些人会担心程序运行完后会不释放，从而导致数据库链接过多而出现崩溃，
首先呢，访问结束时 HttpContext.Items 就会销毁，也就意味着数据库链接也就销毁了，
如果还是不放心，可以在方法执行完成时，将数据库链接手动释放，
首先在工厂类中加上
/// <summary> /// 释放DBContext对象 /// </summary> public static void DisposeDbContext() { if (DemoWeb.HttpContext.Items.ContainsKey("DbContext")) { DemoWeb.HttpContext.Items.Remove("DbContext"); } }
然后不管程序正常执行完成，还是遇到异常，都会走控制器的 OnActionExecuted 方法，因此可以重载这个方法，然后调用释放方法 DbContextFactory.DisposeDbContext();
以上若有什么不对或可以改进的地方，望各位指出或提出意见，一起探讨学习~
有需要源码的可通过此 GitHub 链接拉取 觉得还可以的给个 start 和点个 下方的推荐哦~~谢谢！
从零开始搭建前后端分离的NetCore2.2（EF Core CodeFirst+Autofac）+Vue的项目框架之十数据库基础方法的封装
标签：except 访问 UNC 创建时间 推荐 dea manage 必须 order
原文地址：https://www.cnblogs.com/levywang/p/coreframe_10.html
