Operatorii is si as

Costul operatorilor as is is

static void Main(string[] args)
        {
            object obj = new string('s', 1);
            IsDemo(obj);
            AsDemo(obj);
            ExplicitDemo(obj);
        }
 static void IsDemo(object str)
{
 string local = null;

 if (str is string)
 {
  local = (string)str;
 }
}

.method private hidebysig static void  IsDemo(object str) cil managed
{
  // Code size       29 (0x1d)
  .maxstack  2
  .locals init ([0] string local,
           [1] bool CS$4$0000)
  IL_0000:  nop
  IL_0001:  ldnull
  IL_0002:  stloc.0
  IL_0003:  ldarg.0

-- parametrul este incarcat si se testeaze daca este de tip System.String

  IL_0004:  isinst     [mscorlib]System.String
  IL_0009:  ldnull

-- se incarca pe stiva rezultatul operatiei IL_0004 > IL_0009 (in acest caz e 1)

  IL_000a:  cgt.un
  IL_000c:  ldc.i4.0
  IL_000d:  ceq

-- se calculeaza IL_000a == IL_000a (adica 1 == 0) si se pastreaza rezultatul in loc.1

  IL_000f:  stloc.1
  IL_0010:  ldloc.1

-- daca este adevarat (1 == 0) se sare la instructiunea IL_001c, in acest caz nu se sare

  IL_0011:  brtrue.s   IL_001c
  IL_0013:  nop
  IL_0014:  ldarg.0

-- castul e sigur si se poate face fara aruncarea exceptiei
InvalidCastException

  IL_0015:  castclass  [mscorlib]System.String
  IL_001a:  stloc.0
  IL_001b:  nop
  IL_001c:  ret
} // end of method Program::IsDemo

static void AsDemo(object str)
{
  string local = str as string;
}

.method private hidebysig static void  AsDemo(object str) cil managed
{
  // Code size       9 (0x9)
  .maxstack  1
  .locals init ([0] string local)
  IL_0000:  nop
  IL_0001:  ldarg.0

-- se testeaza daca clasa obiectului incarcat la IL_0001 este un tip derivat al clasei System.String (System.String este derivat din System.String); daca in loc de System.String ar fi fost o interfata testul se rezuma la faptul daca clasa obiectului implementeaza respectiva interfata. In caz de succes se va face castul la System.String. Altfel este incarcat null. Daca obiectul in sine e null, la fel este incarcat null. Nici o exceptie nu e aruncata la runtime (doar la compilare in cazul in care tipul clasei sau interfetei nu este cunoscut de catre compilator se va da o exceptie TypeLoadException)

  IL_0002:  isinst     [mscorlib]System.String
  IL_0007:  stloc.0
  IL_0008:  ret
} // end of method Program::AsDemo

static void ExplicitDemo(object str)
{
   string local = (string)str;
}

.method private hidebysig static void  ExplicitDemo(object str) cil managed
{
  // Code size       9 (0x9)
  .maxstack  1
  .locals init ([0] string local)
  IL_0000:  nop
  IL_0001:  ldarg.0

--Se incearca a se face castul obiectului la clasa System.String. In caz de testul e fara succes va fi aruncata exceptia InvalidCastException. In caz ca obiectul asupra caruia se face castul e null, operatia de cast se considera OK si e returnat noul obiect ca referinta nula (adica null).

  IL_0002:  castclass  [mscorlib]System.String
  IL_0007:  stloc.0
  IL_0008:  ret
} // end of method Program::ExplicitDemo

valoarea medie la fiecare 10 000 iteratii in nanosecunde
Cast cu "is"Cast cu "as"Explicit castString de test
610.21722034504451.766355779854749.7828634644906a
21.483177331197113.912382719032712.3200015644446aa
20.226034314417113.940319230516712.3758745874126aaa
21.455240819713113.912382719032713.2698429549007aaaa
20.253970825901113.940319230516712.3479380759286aaaaa
20.198097802933115.225398758780813.3257159778687aaaaaa
20.253970825901114.024128764968712.3758745874126aaaaaaa
20.281907337385113.968255742000712.4038110988966aaaaaaaa
20.198097802933113.940319230516712.3758745874126aaaaaaaaa
20.253970825901113.968255742000713.7447636501287aaaaaaaaaa

Comments

Post a Comment

Popular posts from this blog

IIS 7.5, HTTPS Bindings and ERR_CONNECTION_RESET

Having an website with HTTP and HTTPS bindings, running on my local IIS 7.5 server, I encountered this error with Chrome, Error 101 (net::ERR_CONNECTION_RESET) while trying to access it with HTTPS protocol. I checked the IIS and the bindings were fine, both protocols were set and self-signed certificate didn't expire yet. Since the website it wasn't accessible on the HTTPS protocol and everything seems ok at the IIS level, I suspected there was something which it can be fixed with the netsh command. The first thing to do was to list the SSL server certificate bindings: netsh http show sslcert As I expected, there was nothing shown. To "add a new SSL server certificate binding and corresponding client certificate policies for an IP address and port" (from help), netsh can be used with some basic parameters: ipport, certhash and appid. The certhash value can be read either from ISS Manager (Manage server\Server Certificates, select a certificate, click View in the ri
Read more

Verify ILogger calls with Moq.ILogger

Moq is by far the most used mocking library for .NET. It provides objects to either mimic real services implementations or to verify if they were called in a certain way by the Service Under Test. Often teams work hard to have meaningful logs in order to help with investigations, to have the possibility to define alarms based on the content of the logs, or even to help with instrumentation. If there is a log entry that resembles as an exception, then a notification might be sent to a Teams/Slack channel, an email, or even to randomly start the alarms on your team's members' cars (joking, don't do that, you know everyone ignores that Slack channel). There are many situations when an investigation ends up with no resolution, and with a promise to the client that the missing logging lines will soon be added. This it translates into development costs, reputation loss, and maybe most importantly having a missed opportunity to learn about the system's behavior in the p
Read more

Table Per Hierarchy Inheritance with Column Discriminator and Associations used in Derived Entity Types

Image
In this article I will show how to model a table per hierarchy, a bit more complex than I found in books or other articles. I'm sure this model is present in real lif,e but I really didn't have the luck to find an example on the web when I needed it most. The complexity of this model is given by the Foreign Keys ( the Associations) which need to be placed in the derived entities types and the fact the discriminator depends on more than one column. The first problem I could fix, but the next one, with the discriminator based on two or three nullable columns I couldn't do it, unless if I use a single discriminator column (ie ItemType or something). The database is very simple. It is designed for an eshop which sells products, services and also has some nice packages, that combines products and services and offers them for good prices compared with if they would be bought alone. The products and services are very different in terms of how data describes them, so the decision
Read more