目录
一.EF修改和删除的多种方法
方法1：官方推荐 先查询在修改 或者删除
1 var student = db.Students.FirstOrDefault(t => t.Id == Mid); 2 student.Name = "修改后";//修改值数据 3 db.SaveChanges();//保存 4 db.Students.Remove(student);//移除对象 5 db.SaveChanges();//保存
方法2：先附加到ef实体对象 然后在移除
1 Students s = new Students(); 2 s.Id = int.Parse(id); 3 db.Students.Attach(s);//将实体附加到 上下文中 ； 4 db.Students.Remove(s); 5 if (db.SaveChanges() >= 1) 6 { 7 //成功 8 }
方法3：添加到ef实体对象 然后标记删除
1 Students s = new Students(); 2 s.Id = int.Parse(id); 3 db.Entry<Students>(s).State = System.Data.EntityState.Deleted;//标记删除 4 int num = db.SaveChanges();
方法4：修改实体
1 //这里需要关闭验证 不然会报错 2 db.Configuration.ValidateOnSaveEnabled = false; 3 DbEntityEntry dbS = db.Entry<Students>(s); 4 dbS.State = System.Data.EntityState.Unchanged; //清楚所有字段标记 5 dbS.Property("Gender").IsModified = true;//标记修改字段 6 int num = db.SaveChanges(); 7 db.Configuration.ValidateOnSaveEnabled = true;//打开验证 8 if (num >= 1) 9 { 10 //修改成功 11 }
二.标准查询where 在不同场景 实现方法不一样
1 //场景1：ef的数据集 使用where 是在 IQueryable 的扩展方法 2 //场景2：List集合的数据集 使用where 是在 IEnumerable 的扩展方法
三.include
场景1：自动 连接查询【无Include】
1 //1.自动 连接查询【无Include】 2 var stu1 = db.Students.Where(t => t.Classes.CName == "zha"); 3 var cname = stu1.FirstOrDefault();
1 SELECT TOP (1) 2 [Extent1].[Id] AS [Id], 3 [Extent1].[CId] AS [CId], 4 [Extent1].[Name] AS [Name], 5 [Extent1].[Gender] AS [Gender], 6 [Extent1].[IsDel] AS [IsDel], 7 [Extent1].[AddTime] AS [AddTime] 8 FROM [dbo].[Students] AS [Extent1] 9 INNER JOIN [dbo].[Classes] AS [Extent2] ON [Extent1].[CId] = [Extent2].[CID] 10 WHERE 'zha' = [Extent2].[CName]
场景2：手动 内连接查询【有Include】
1 //2手动 内连接查询【有Include】 2 var stu2 = db.Students.Include("Classes").Where(t => t.Id == 11); 3 var ccc = stu2.FirstOrDefault().Classes.CName;
1 SELECT 2 [Limit1].[Id] AS [Id], 3 [Limit1].[CId] AS [CId], 4 [Limit1].[Name] AS [Name], 5 [Limit1].[Gender] AS [Gender], 6 [Limit1].[IsDel] AS [IsDel], 7 [Limit1].[AddTime] AS [AddTime], 8 [Extent2].[CID] AS [CId1], 9 [Extent2].[CName] AS [CName], 10 [Extent2].[CCount] AS [CCount], 11 [Extent2].[CImg] AS [CImg], 12 [Extent2].[CIsDel] AS [CIsDel], 13 [Extent2].[CAddTime] AS [CAddTime] 14 FROM (SELECT TOP (1) [Extent1].[Id] AS [Id], [Extent1].[CId] AS [CId], [Extent1].[Name] AS [Name], [Extent1].[Gender] AS [Gender], [Extent1].[IsDel] AS [IsDel], [Extent1].[AddTime] AS [AddTime] 15 FROM [dbo].[Students] AS [Extent1] 16 WHERE 11 = [Extent1].[Id] ) AS [Limit1] 17 LEFT OUTER JOIN [dbo].[Classes] AS [Extent2] ON [Limit1].[CId] = [Extent2].[CID]
场景3：无连接查询 分两次sql查询【无Include】
1 //3.无连接查询 分两次sql查询【无Include】 2 var stucc = db.Students.Where(t => t.Id == 11); 3 var zz = stucc.FirstOrDefault().Classes.CName;
1 SELECT TOP (1) 2 [Extent1].[Id] AS [Id], 3 [Extent1].[CId] AS [CId], 4 [Extent1].[Name] AS [Name], 5 [Extent1].[Gender] AS [Gender], 6 [Extent1].[IsDel] AS [IsDel], 7 [Extent1].[AddTime] AS [AddTime] 8 FROM [dbo].[Students] AS [Extent1] 9 WHERE 11 = [Extent1].[Id]; 10 11 SELECT 12 [Extent1].[CID] AS [CID], 13 [Extent1].[CName] AS [CName], 14 [Extent1].[CCount] AS [CCount], 15 [Extent1].[CImg] AS [CImg], 16 [Extent1].[CIsDel] AS [CIsDel], 17 [Extent1].[CAddTime] AS [CAddTime] 18 FROM [dbo].[Classes] AS [Extent1] 19 WHERE [Extent1].[CID] = @EntityKeyValue1
四.skip take
1 //Skip 跳过序列中指定数量的元素，然后返回剩余的元素。 2 //Take 从序列的开头返回指定数量的连续元素。 3 //根据这两个方法可以 实现 分页效果
五.反射获取实例属性
1 //利用反射 获取 类 对象 的所有公共 属性 默认是[GetProperties(BindingFlags.Instance | BindingFlags.Public)] 2 var listPro = typeof(Students).GetProperties().ToList(); 3 object obj1 = new object(); 4 object obj2 = new object(); 5 listPro.ForEach(l => 6 { 7 var newValue = l.GetValue(obj1); //获得某个对象的属性值 8 l.SetValue(obj2, newValue);//修改一个对象的属性 值 9 });
六.EF DLL数据访问帮助 父类
1 using _00EFModel; 2 using System; 3 using System.Collections.Generic; 4 using System.Linq; 5 using System.Linq.Expressions; 6 using System.Reflection; 7 using System.Text; 8 using System.Threading.Tasks; 9 10 namespace _00EFDLL 11 { 12 /// <summary> 13 /// 数据访问 父类 14 /// </summary> 15 public class BaseDLL<Tclass> where Tclass : class,new() 16 { 17 /// <summary> 18 /// 数据访问上下文 19 /// </summary> 20 _00EFModel.Entities db = new _00EFModel.Entities(); 21 22 #region 1.0添加数据 + Add(Tclass model) 23 /// <summary> 24 /// 1.0添加数据 25 /// </summary> 26 /// <param name="model"></param> 27 public void Add(Tclass model) 28 { 29 db.Set<Tclass>().Add(model); 30 } 31 #endregion 32 33 #region 2.0 删除方法1 删除给定的对象 +Del(Tclass model) 34 /// <summary> 35 /// 2.0 删除方法1 删除给定的对象 36 /// </summary> 37 /// <param name="model"></param> 38 public void Del(Tclass model) 39 { 40 //将实体 添加到上下文 41 db.Set<Tclass>().Attach(model); 42 //把实体 标记为删除 43 db.Set<Tclass>().Remove(model); 44 } 45 #endregion 46 47 #region 2.1 删除方法2 根据条件删除对象 +Del(Expression<Func<Tclass, bool>> delWhere) 48 /// <summary> 49 /// 2.1 删除方法2 根据条件删除对象 50 /// </summary> 51 /// <param name="delWhere"></param> 52 public void Del(Expression<Func<Tclass, bool>> delWhere) 53 { 54 //查询所有满足条件的实体对象 55 var modelS = db.Set<Tclass>().Where(delWhere).ToList(); 56 modelS.ForEach(m => 57 { 58 //附加到 上下文 59 db.Set<Tclass>().Attach(m); 60 //标记为 删除状态 61 db.Set<Tclass>().Remove(m); 62 }); 63 } 64 #endregion 65 66 #region 3.0 修改方法1 修改某个实体的 某些属性 +Up(Tclass model, params string[] strparams) 67 /// <summary> 68 /// 3.0 修改方法1 修改某个实体的 某些属性(根据id修改)【*用这个需要注意关闭检查】 69 /// </summary> 70 /// <param name="model"></param> 71 /// <param name="strparams">可变参数</param> 72 public int Up(Tclass model, params string[] strparams) 73 { 74 //关闭检查 75 db.Configuration.ValidateOnSaveEnabled = false; 76 //附加到上下文 77 var m = db.Entry<Tclass>(model); 78 //把全部属性标记为 没有修改 79 m.State = System.Data.Entity.EntityState.Unchanged; 80 for (int i = 0; i < strparams.Length; i++) 81 { 82 //标记要修改的属性 83 m.Property(strparams[i]).IsModified = true; 84 } 85 int num = db.SaveChanges(); 86 //打开检查 87 db.Configuration.ValidateOnSaveEnabled = true; 88 return num; 89 } 90 #endregion 91 92 #region 3.1 修改方法2 根据条件 修改指定的 属性 值 +Up(Expression<Func<Tclass, bool>> upWhere, Tclass model, params string[] strparame) 93 /// <summary> 94 /// 3.1 修改方法2 根据条件 修改指定的 属性 值 95 /// </summary> 96 /// <param name="upWhere"></param> 97 /// <param name="model"></param> 98 /// <param name="strparame"></param> 99 public void Up(Expression<Func<Tclass, bool>> upWhere, Tclass model, params string[] strparame) 100 { 101 //查询出满足条件的所有实体 102 var modelS = db.Set<Tclass>().Where(upWhere).ToList(); 103 //利用反射 获取 类 对象 的所有公共 属性 默认是[GetProperties(BindingFlags.Instance | BindingFlags.Public)] 104 var listPro = typeof(Tclass).GetProperties().ToList(); 105 // 属性对象 键值对 106 List<PropertyInfo> dic = new List<PropertyInfo>(); 107 listPro.ForEach(l => 108 { 109 for (int i = 0; i < strparame.Length; i++) 110 { 111 //循环 判断 添加 需要修改的 属性对象 112 if (l.Name == strparame[i].Trim()) 113 { 114 dic.Add(l); 115 break; 116 } 117 } 118 }); 119 120 if (dic.Count > 0)//判断 属性对象集合 是否 有 数据 121 { 122 foreach (var property in dic) 123 { 124 //取 传过来的对象 里面的值 125 var newValue = property.GetValue(model); 126 foreach (var mymodel in modelS) 127 { 128 //修改到 对象集合 129 property.SetValue(mymodel, newValue); 130 } 131 } 132 } 133 } 134 #endregion 135 136 #region 4.0 查询方法 +GetList<Tkey>(Expression<Func<Tclass, bool>> strWhere, Expression<Func<Tclass, Tkey>> strOrederBy = null, bool order = true) 137 /// <summary> 138 /// 4.0 查询方法 139 /// </summary> 140 /// <typeparam name="Tkey"></typeparam> 141 /// <param name="strWhere">查询条件</param> 142 /// <param name="strOrederBy">排序条件</param> 143 /// <param name="order">是否升序</param> 144 /// <returns></returns> 145 public List<Tclass> GetList<Tkey>(Expression<Func<Tclass, bool>> strWhere, Expression<Func<Tclass, Tkey>> strOrederBy = null, bool order = true) 146 { 147 var t = db.Set<Tclass>().Where(strWhere); 148 if (strOrederBy != null) 149 { 150 if (order) 151 t = t.OrderBy(strOrederBy); 152 else 153 t = t.OrderByDescending(strOrederBy); 154 } 155 return t.ToList(); 156 } 157 #endregion 158 159 #region 4.1 查询方法2 分页查询 +GetList<Tkey>(int indexPage, int sizePage, Expression<Func<Tclass, bool>> strWhere, Expression<Func<Tclass, Tkey>> strOrederBy = null, bool order = true) 160 /// <summary> 161 /// 4.1 查询方法2 分页查询 162 /// </summary> 163 /// <typeparam name="Tkey"></typeparam> 164 /// <param name="indexPage">页码</param> 165 /// <param name="sizePage">页容量</param> 166 /// <param name="strWhere">查询条件</param> 167 /// <param name="strOrederBy">排序字段</param> 168 /// <param name="order">是否升序</param> 169 /// <returns></returns> 170 public List<Tclass> GetList<Tkey>(int indexPage, int sizePage, Expression<Func<Tclass, bool>> strWhere, Expression<Func<Tclass, Tkey>> strOrederBy = null, bool order = true) 171 { 172 var t = db.Set<Tclass>().Where(strWhere); 173 if (strOrederBy != null) 174 { 175 if (order) 176 t = t.OrderBy(strOrederBy); 177 else 178 t = t.OrderByDescending(strOrederBy); 179 } 180 return t.Skip((indexPage - 1) * sizePage).Take(sizePage).ToList(); 181 } 182 #endregion 183 184 #region 提交 +save() 185 /// <summary> 186 /// 提交 187 /// </summary> 188 /// <returns></returns> 189 public int save() 190 { 191 return db.SaveChanges(); 192 } 193 #endregion 194 } 195 }
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