Today, when I read "LINQ in action", I suddenly came up with the idea of using expression and LINQ to quickly access object attributes. If we put an object in an array for query, and then use select to project the required attributes, we can achieve quick access. Although it is much slower than direct access, it is still very good that it is faster than the reflection method by an order of magnitude. Assume that an object class is defined as follows: public class user
...{
Public string name
... {Get; set ;}
Public int age
... {Get; set ;}
} If we want to access the value of the Name field, VAR books = new user []... {new user... {name = "Lucifer", age = 26 }};
Var val = books. select (Book => book. name ). first (); it's very simple, right? Next, you just need to translate it with expression and compile it into a generic one. The Code is as follows: using system;
Using system. Collections. Generic;
Using system. LINQ;
Using system. LINQ. expressions;
Using system. diagnostics;
Public class quickaccess <t>
...{
Static dictionary <int, delegate> _ pmap = new dictionary <int, delegate> ();
Static T [] _ lst = new T []... {default (t )};
Public static P get_properyval <p> (t obj, string pname)
...{
VaR func = default (func <T, P> );
_ Lst [0] = OBJ;
Try
...{
Func = (func <T, P>) _ pmap [pname. gethashcode ()];
}
Catch
...{
/**//*
* From Param in _ lst
* Select Param. pname
**/
VaR Param = expression. parameter (typeof (t), "Param ");
VaR body = expression. Property (Param, pname );
VaR Lambda = expression. Lambda (body, Param );
_ Pmap. Add (pname. gethashcode (), lambda. Compile ());
Func = (func <T, P>) _ pmap [pname. gethashcode ()];
}
Return enumerable. Select (_ lst, func). First ();
}
}
// Call the code
Int val = 0;
VaR user = new user... {name = "Lucifer", age = 26 };
Stopwatch SW1 = new stopwatch ();
Sw1.start ();
For (INT I = 0; I <10000000; ++ I)
...{
Val = quickaccess <user>. get_properyval <int> (user, "Age ");
}
Sw1.stop ();
Console. writeline (sw1.elapsedmilliseconds.
