The use of the Select and where of Linq

Recently began to learn LINQ. You can also summarize it for your convenience.

Select is similar to select in SQL, which outputs what we want, and feels more powerful in LINQ.

Linq can operate on collections such as arrays, generics, and so on, where we give examples of generic types. Build a class like this:

 Public classCustomer { PublicCustomer (stringFirstName,stringLastName,stringCity ) {FirstName=FirstName; LastName=LastName; City=City ; }   PublicCustomer () {} Public stringFirstName {Get;Set; }  Public stringLastName {Get;Set; }  Public stringCity {Get;Set; } }  

1 . Select Out object,Cust is a Customer object.

Static voidMain (string[] args) {List<Customer> customers =NewList<customer>()               {                   NewCustomer ("Jack","Chen","London"),                  NewCustomer ("Sunny","Peng","Shenzhen"),                  NewCustomer ("Tom","Cat","London")              }; //using ienumerable<t> as a variable            varresult = fromCustinchCustomerswhereCust. City = ="London"                          SelectCust; foreach(varIteminchresult) {Console.WriteLine (item. FirstName+":"+item.              City);          } console.read (); }  

2. Select the attribute field for the object

var result =from in"London"           Select Cust. City  

Multiple properties are to be used with new {} as follows:

var result =from inwhere"London"                          Select  new{Cust. City,cust. FirstName};  

3. Rename, city and name are random

varresult = fromCustinchCustomerswhereCust. City = ="London"                          Select New{City=cust. City, name ="name"+ Cust. firstname+""+Cust.              LastName}; foreach(varIteminchresult) {Console.WriteLine (Item.name+":"+item.city); }  

4. Direct instantiation of objects

var result =from inwhere"London"           SelectNew

5. nested Select in Selec

var result = from in Customers  where"London"              Selectnew{city = Cust. City,   name=from inwhere"London" Select Cust1. LastName  };  

The use of the Select and where of Linq