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
/// <summary>
/// 根据条件查询
/// </summary>
/// <param name="UserID"></param>
/// <returns></returns>
public List<User> GetUser(string UserID)
{
using (FamilyServerEntities Family = new FamilyServerEntities())
{
List<User> users = Family.User.Where(a => a.UserID == UserID).ToList();
return users;
}
}
根据条件修改
/// <summary>
/// 根据条件修改
/// </summary>
/// <param name="UserID"></param>
/// <param name="UserName"></param>
/// <returns></returns>
public User 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 user;
}
}
增加数据
/// <summary>
/// 添加数据
/// </summary>
/// <param name="user"></param>
/// <returns></returns>
public User 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 user;
}
else
return null;
}
}
增加多条
/// <summary>
/// 添加多条
/// </summary>
/// <param name="user"></param>
/// <returns></returns>
public List<User> UserADDList(List<User> user)
{
using (FamilyServerEntities Family = new FamilyServerEntities())
{
for (int i = 0; i < user.Count; i++)
{
Family.User.Add(
new User()
{
UserID = user[i].UserID,
UserName = user[i].UserName,
UserSet = user[i].UserSet
});
}
if (Family.SaveChanges() > 0)
{
return user;
}
else
return null;
}
}
根据条件删除数据
/// <summary>
/// 根据条件删除数据
/// </summary>
/// <param name="UserID"></param>
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)
{
}
}
}
查询多表
/// <summary>
/// 查询多表
/// </summary>
/// <returns></returns>
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。
来源：https://www.cnblogs.com/jstblog/p/12293812.html