In previous post http://marisolca.blogspot.com/2015/09/linq.html we made queries that do not get really until produce the iteration on it,it is a default behavior of LINQ, but if we want to "cache" in memory the result of the query to reuse.We will use the standard operators as ToArray<T>(),ToList<T>(),ToDictionary<T,K>() and ToLookup<T,K,E>()
For Example,we want to get the name of employees that start with letter "A"
Our class Employee
Our method gets a list of employees
Create a test method to see the result of deferred execution
Using the standard operators
The result of the execution
Syntax the query expressions
<Expression query>::=<FROM clause><body clause>
<FROM clause>::=FROM<element> IN<origin expression>
<body clause>::=<body clause query>*
<end clause query>
<continuation > ?
<body clause query>::= (<FROM clause>
| <JOIN clause>
| <JOIN-INTO clause>
| <LET clause>
| <WHERE clause>
|<ORDERBY clause>)
<LET clause>::=LET<element>=<Expresion.selection>
<WHERE clause> ::=WHERE<expression.filter>
<JOIN clause>::=JOIN<element> IN <expresion.origin>
ON<Expression.key> EQUALS<expression.key>
<JOIN-INTO clause>::= JOIN<element> IN <expression.origin>
ON<expression.key> EQUALS<expression.key>
INTO<element>
<ORDERBY clause>::= ORDERBY<ordinations>
<ordinations>::=<ordination>| <ordinations>,<ordination>
<ordination>:=<expression.key>(ascending | descending)?
<end clause query>::=(<SELECT clause> | <GROUPBY clause>
<SELECT clause>::=SELECT<expression.selection>
<GROUPBY clause>::=GROUP<expression.selection> BY<expression.key>
<continuation>::INTO<element><body query>
Meta-language :
* - zero or more times
(.... | ....) - alternative
? - optional element
In the following post, we will do examples the queries
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