Lambda表达式实际上是一个匿名函数，它可以说是对LINQ的补充。
由于LINQ查询关键字和IEnumerable接口的方法之间有一个对应关系，但是LINQ查询表达式中可以使用的查询功能很少。
在实际开发中通过查询结果或数据源进行方法调用，从而进行更多的查询操作。
由于Lambda表达式是匿名函数，它可以赋值到一个委托，而在IEnumerable接口的方法中很多通过函数委托来实现自定义运算、条件等操作，所以Lambda表达式在LINQ中被广泛使用。
详情请查阅：https://www.php.cn/csharp-article-353245.html
根据条件查询
////// 根据条件查询 /// /// /// public List GetUser(string UserID) { using (FamilyServerEntities Family = new FamilyServerEntities()) { List users = Family.User.Where(a => a.UserID == UserID).ToList(); return users; } }
根据条件修改
////// 根据条件修改 /// /// /// /// public static int Update(string UserID, string UserName) { using (FamilyServerEntities Family = new FamilyServerEntities()) { //根据条件查询出来 User user = Family.User.Where(a => a.UserID == UserID).FirstOrDefault(); if (user != null) { //修改指定数据 user.UserName = UserName; //保存 Family.SaveChanges(); return 1; } return 0; } }
修改多条
////// 修改多条 /// /// /// public static int Edits(List list) { using (FamilyServerEntities Family = new FamilyServerEntities()) { User user = Family.User.FirstOrDefault(); if (user != null) { foreach (var item in list) { user.UserName = item.UserName; Family.SaveChanges(); } return 1; } return 0; } }
增加数据
////// 添加数据 /// /// /// public static int UserADD(User user) { using (FamilyServerEntities Family = new FamilyServerEntities()) { Family.User.Add( new User() { UserID = user.UserID, UserName = user.UserName, UserSet = user.UserSet }); if (Family.SaveChanges() > 0) { return 1; } else return 0; } }
增加多条
////// 添加多条 /// /// /// public List UserADDList(List user) { using (FamilyServerEntities Family = new FamilyServerEntities()) { if (user.Count > 0) { foreach (var item in user) { Family.User.Add(new User() { UserID = item.UserID, UserName = item.UserName, UserSet = item.UserSet }); } if (Family.SaveChanges() > 0) { return user; } else return null; } return null; } }
根据条件删除数据
////// 根据条件删除数据 /// /// public void Deleted(string UserID) { using (FamilyServerEntities Family = new FamilyServerEntities()) { //根据条件查询出一条数据到user User user = Family.User.Where(a => a.UserID == UserID).FirstOrDefault(); if (user != null) { //如果有数据那么就删除 并且保存 Family.User.Remove(user); } if (Family.SaveChanges() > 0) { } } }
删除多条数据
////// 根据条件删除多条数据 /// /// public int Deleted(string UserID) { using (FamilyServerEntities Family = new FamilyServerEntities()) { //根据条件查询数据到user List user = Family.User.Where(a => a.UserID == UserID).ToList(); if (user != null) { foreach (var item in user) { Family.User.Remove(item); } } return Family.SaveChanges(); } }
查询多表
////// 查询多表 /// /// public static User Getuser() { using (FamilyServerEntities Family = new FamilyServerEntities()) { User user = new User(); var result = Family.User.GroupJoin(Family.Work, u => u.UserworkID, w => w.UserworkID, (u, w) => new { Work = w, u.UserID, u.UserName, u.UserSet, u.Userphone, u.UserCreationtime, u.UserlevelID, u.UserTypeID, u.UserhobbyID }).SelectMany(u => u.Work, (u, w) => new { u.UserID, u.UserName, u.UserSet, u.Userphone, u.UserCreationtime, u.UserlevelID, u.UserTypeID, u.UserhobbyID, w.WorkDetailsID, w.UserworkType }).GroupJoin(Family.level, u => u.UserlevelID, l => l.UserlevelID, (u, l) => new { level = l, u.UserID, u.UserName, u.UserSet, u.Userphone, u.UserCreationtime, u.UserworkType, u.UserTypeID, u.UserhobbyID, u.WorkDetailsID, }).SelectMany(u => u.level, (u, l) => new { u.UserID, u.UserName, u.UserSet, u.Userphone, u.UserCreationtime, u.UserTypeID, u.UserhobbyID, u.WorkDetailsID, u.UserworkType, l.UserleverlType }).GroupJoin(Family.UserType, u => u.UserTypeID, t => t.UserTypeID, (u, t) => new { UserType = t, u.UserID, u.UserName, u.UserSet, u.Userphone, u.UserCreationtime, u.UserTypeID, u.UserhobbyID, u.WorkDetailsID, u.UserworkType, u.UserleverlType }).SelectMany(u => u.UserType, (u, t) => new { u.UserID, u.UserName, u.UserSet, u.Userphone, u.UserCreationtime, t.UserType1, u.UserhobbyID, u.WorkDetailsID, u.UserworkType, u.UserleverlType }).GroupJoin(Family.WorkDetails, u => u.WorkDetailsID, d => d.WorkDetailsID, (u, d) => new { WorkDetails = d, u.UserID, u.UserName, u.UserSet, u.Userphone, u.UserCreationtime, u.UserType1, u.UserhobbyID, u.WorkDetailsID, u.UserworkType, u.UserleverlType }).SelectMany(u => u.WorkDetails, (u, d) => new { u.UserID, u.UserName, u.UserSet, u.Userphone, u.UserCreationtime, u.UserType1, u.UserhobbyID, d.WorkDetailsSituation, u.UserworkType, u.UserleverlType }).GroupJoin(Family.Userhobby, u => u.UserhobbyID, h => h.UserhobbyID, (u, h) => new { Userhobby = h, u.UserID, u.UserName, u.UserSet, u.Userphone, u.UserCreationtime, u.UserType1, u.UserhobbyID, u.WorkDetailsSituation, u.UserworkType, u.UserleverlType }).SelectMany(u => u.Userhobby, (u, h) => new { u.UserID, u.UserName, u.UserSet, u.Userphone, u.UserCreationtime, u.UserType1, u.WorkDetailsSituation, u.UserworkType, u.UserleverlType, h.Userhobby1 }).Select(u => new { UserID = u.UserID, UserName = u.UserName, UserSet = u.UserSet, Userphone = u.Userphone, UserCreationtime = u.UserCreationtime, UserType1 = u.UserType1, WorkDetailsSituation = u.WorkDetailsSituation, UserworkType = u.UserworkType, UserleverlType = u.UserleverlType, Userhobby1 = u.Userhobby1 }).ToList(); if (result.Count > 0) { for (int i = 0; i < result.Count; i++) { foreach (var item in result) { user.UserID = item.UserID; user.UserName = item.UserName; user.UserSet = item.UserSet; user.Userphone = item.Userphone; } } } return user; } }
数据库
总结一下：其实挺简单的
好了废话不多少了，我滚了。