public static void Show()
{
{
Expression <Func <int, int, int> > exp = (m, n) => m * n + 2 + 3 + Get(m);
// Change the expression exp to m*n -2
OperationsVisitor visitor = new OperationsVisitor();
Expression expNew = visitor.Modify(exp);
}
{
///Parse a lambda to a sql script, parse where condition
///ORM maps the database to program memory and manages the database by manipulating objects
///Developers don't need to know details of database.
var source = new List <People>().AsQueryable();
var result = source.Where <People>(p => p.Age > 5)
.Where(p => p.Name.Equals("124"))
.Where(p => p.Age < 10);
//.ToList() //Only here execute the sql
Expression <Func <People, bool> > lambda = x => x.Age > 5;
ConditionBuilderVisitor visitor = new ConditionBuilderVisitor();
visitor.Visit(lambda);
Console.WriteLine(visitor.Condition());
}
{
Expression <Func <People, bool> > lambda = x => x.Age > 5 && x.Id > 5 &&
x.Name.StartsWith("1") &&
x.Name.EndsWith("1") &&
x.Name.Contains("1");
string sql = string.Format("Delete From [{0}] WHERE {1}", typeof(People).Name, "[Age]>5 AND [ID]>5");
ConditionBuilderVisitor visitor = new ConditionBuilderVisitor();
visitor.Visit(lambda);
var result = visitor.Condition();
Console.WriteLine(result);
// Queryable is to parse linq to sql script
}
{
Expression <Func <People, bool> > lambda = x => x.Age > 5 && x.Name == "A" || x.Id > 5;
Expression <Func <People, bool> > lambda1 = x => x.Age > 5 || (x.Name == "A" && x.Id > 5);
Expression <Func <People, bool> > lambda2 = x => (x.Age > 5 || x.Name == "A") && x.Id > 5;
ConditionBuilderVisitor vistor = new ConditionBuilderVisitor();
vistor.Visit(lambda);
Console.WriteLine(vistor.Condition());
vistor.Visit(lambda1);
Console.WriteLine(vistor.Condition());
vistor.Visit(lambda2);
Console.WriteLine(vistor.Condition());
}
{
//Link expression
Expression <Func <People, bool> > lambda1 = x => x.Age > 5;
Expression <Func <People, bool> > lambda2 = x => x.Id > 5;
}
}
public static void Show()
{
{
//修改表达式目录树
Expression <Func <int, int, int> > exp = (m, n) => m * n + 2;
OperationsVisitor visitor = new OperationsVisitor();
//visitor.Visit(exp);
Expression expNew = visitor.Modify(exp);
}
{
Expression <Func <People, bool> > lambda = x => x.Age > 5 && x.Id > 5 &&
x.Name.StartsWith("1") &&
x.Name.EndsWith("1") &&
x.Name.Contains("1");
string sql = string.Format("Delete From [{0}] WHERE {1}"
, typeof(People).Name
, " [Age]>5 AND [ID] >5"
);
ConditionBuilderVisitor vistor = new ConditionBuilderVisitor();
vistor.Visit(lambda);
Console.WriteLine(vistor.Condition());
}
{
Expression <Func <People, bool> > lambda = x => x.Age > 5 && x.Name == "A" || x.Id > 5;
ConditionBuilderVisitor vistor = new ConditionBuilderVisitor();
vistor.Visit(lambda);
Console.WriteLine(vistor.Condition());
}
{
Expression <Func <People, bool> > lambda = x => x.Age > 5 || (x.Name == "A" && x.Id > 5);
ConditionBuilderVisitor vistor = new ConditionBuilderVisitor();
vistor.Visit(lambda);
Console.WriteLine(vistor.Condition());
}
{
Expression <Func <People, bool> > lambda = x => (x.Age > 5 || x.Name == "A") && x.Id > 5;
ConditionBuilderVisitor vistor = new ConditionBuilderVisitor();
vistor.Visit(lambda);
Console.WriteLine(vistor.Condition());
}
#region 表达式链接
{
Expression <Func <People, bool> > lambda1 = x => x.Age > 5;
Expression <Func <People, bool> > lambda2 = x => x.Id > 5;
Expression <Func <People, bool> > lambda3 = lambda1.And(lambda2);
Expression <Func <People, bool> > lambda4 = lambda1.Or(lambda2);
Expression <Func <People, bool> > lambda5 = lambda1.Not();
Do1(lambda3);
Do1(lambda4);
Do1(lambda5);
}
#endregion
}
public static void Show()
{
{
Expression <Func <int, int, int> > exp = (m, n) => m * n + 2;
OperationsVisitor visitor = new OperationsVisitor();
Expression exp1 = visitor.Visit(exp);
Expression expression = visitor.Modify(exp);
}
{
Expression <Func <People, bool> > exp = (p) => p.Age > 5 && p.Id > 5 && p.Name.StartsWith("t");
ConditionBuilderVisitor cond = new ConditionBuilderVisitor();
cond.Visit(exp);
string sResult = cond.Condition();
}
}
public static void Show()
{
{
//修改表达式目录树
Expression <Func <int, int, int> > exp = (m, n) => m * n + 2 + 3 + Get(m);
//我想修改下，变成m*n-2
OperationsVisitor visitor = new OperationsVisitor();
//visitor.Visit(exp);
Expression expNew = visitor.Modify(exp);
}
{
var source = new List <People>().AsQueryable();//DbSet
var result = source.Where <People>(p => p.Age > 5)
.Where(p => p.Name.Equals("123"))
.Where(p => p.Age < 10)
//.ToList()
; //SELECT * FROM People Where Age> '5'
Expression <Func <People, bool> > lambda = x => x.Age > 5;
ConditionBuilderVisitor vistor = new ConditionBuilderVisitor();
vistor.Visit(lambda);
Console.WriteLine(vistor.Condition());
}
{
//ORM 把数据库映射到程序内存 通过操作对象来完成对数据库的管理
//屏蔽数据库，开发者完全不需要知道
//Linq To Object 实现IEnumerable
//Enumerable
//Queryable
//IQueryable
Expression <Func <People, bool> > lambda = x => x.Age > 5 && x.Id > 5 &&
x.Name.StartsWith("1") &&
x.Name.EndsWith("1") &&
x.Name.Contains("1");
string sql = string.Format("Delete From [{0}] WHERE {1}"
, typeof(People).Name
, " [Age]>5 AND [ID] >5"
);
ConditionBuilderVisitor vistor = new ConditionBuilderVisitor();
vistor.Visit(lambda);
Console.WriteLine(vistor.Condition());
}
{
Expression <Func <People, bool> > lambda = x => x.Age > 5 && x.Name == "A" || x.Id > 5;
ConditionBuilderVisitor vistor = new ConditionBuilderVisitor();
vistor.Visit(lambda);
Console.WriteLine(vistor.Condition());
}
{
Expression <Func <People, bool> > lambda = x => x.Age > 5 || (x.Name == "A" && x.Id > 5);
ConditionBuilderVisitor vistor = new ConditionBuilderVisitor();
vistor.Visit(lambda);
Console.WriteLine(vistor.Condition());
}
{
Expression <Func <People, bool> > lambda = x => (x.Age > 5 || x.Name == "A") && x.Id > 5;
ConditionBuilderVisitor vistor = new ConditionBuilderVisitor();
vistor.Visit(lambda);
Console.WriteLine(vistor.Condition());
}
#region 表达式链接
{
Expression <Func <People, bool> > lambda1 = x => x.Age > 5;
Expression <Func <People, bool> > lambda2 = x => x.Id > 5;
Expression <Func <People, bool> > lambda3 = lambda1.And(lambda2);
Expression <Func <People, bool> > lambda4 = lambda1.Or(lambda2);
Expression <Func <People, bool> > lambda5 = lambda1.Not();
Do1(lambda3);
Do1(lambda4);
Do1(lambda5);
}
#endregion
}
//表达式目录树的拼装和拆解作为本周的家庭作业
public static void Show()
{
//ExpressionVisitor访问者类，Visit是一个入口，先判断，进一步的解析，然后
//1、lambada会区分参数和方法体，调度到更加专业的方法中解析；
//2、根据表达式的类型，调度到更加专业的方法中解析；
//3、默认根据旧的模式产生一个新的表达式目录树；
// 解析表达式目录树的时候，先从Visit进入，调度更加专业的方法进一步解析；
{
//修改表达式目录树
Expression <Func <int, int, int> > exp = (m, n) => m * n + 2;
OperationsVisitor visitor = new OperationsVisitor();
//visitor.Visit(exp);
Expression expNew = visitor.Modify(exp);
}
{
// 写成这样的表达式目录树怎么变成sql呢？
Expression <Func <People, bool> > lambda = x => x.Age > 5;
// select * from People where Age>5
new List <People>().AsQueryable().Where(x => x.Age > 5 && x.Id == 10);
ConditionBuilderVisitor vistor = new ConditionBuilderVisitor();
vistor.Visit(lambda);
Console.WriteLine(vistor.Condition());
}
Console.WriteLine("更加复杂一点");
{
//select * from People where Age>5 and Id>5
Expression <Func <People, bool> > lambda = x => x.Age > 5 &&
x.Id > 5 &&
x.Name.StartsWith("1") &&
x.Name.EndsWith("1") &&
x.Name.Contains("1");
string sql = string.Format("Delete From [{0}] WHERE {1}"
, typeof(People).Name
, " [Age]>5 AND [ID] >5"
);
ConditionBuilderVisitor vistor = new ConditionBuilderVisitor();
vistor.Visit(lambda);
Console.WriteLine(vistor.Condition());
}
{
//且或非
Expression <Func <People, bool> > lambda = x => x.Age > 5 && x.Name == "A" || x.Id > 5;
ConditionBuilderVisitor vistor = new ConditionBuilderVisitor();
vistor.Visit(lambda);
Console.WriteLine(vistor.Condition());
}
{
Expression <Func <People, bool> > lambda = x => x.Age > 5 || (x.Name == "A" && x.Id > 5);
ConditionBuilderVisitor vistor = new ConditionBuilderVisitor();
vistor.Visit(lambda);
Console.WriteLine(vistor.Condition());
}
{
Expression <Func <People, bool> > lambda = x => (x.Age > 5 || x.Name == "A") && x.Id > 5;
ConditionBuilderVisitor vistor = new ConditionBuilderVisitor();
vistor.Visit(lambda);
Console.WriteLine(vistor.Condition());
}
#region 表达式链接
{
// 把多个表达式拼接起来
Expression <Func <People, bool> > lambda1 = x => x.Age > 5;
Expression <Func <People, bool> > lambda2 = x => x.Id > 5;
Expression <Func <People, bool> > lambda3 = lambda1.And(lambda2);
Expression <Func <People, bool> > lambda4 = lambda1.Or(lambda2);
Expression <Func <People, bool> > lambda5 = lambda1.Not();
Do1(lambda3);
Do1(lambda4);
Do1(lambda5);
}
#endregion
}