发信人: nice (春天), 信区: DotNET        
标  题: C#快餐－19
发信站: BBS 水木清华站 (Thu Jul 26 02:22:10 2001)

Lesson 19. Creating components with C#


   According to Microsoft's marketing, component development is vastly  
simplified in .Net framework. Windows operating system consists of thousands  
and thousands of dlls. These dlls need to be accessed by application dlls  
which must interoperate with each other as well as with the operating system.  
Creating and managing dll files  takes a lot of windows developer resources.
Every new version of an application must come with the new version of the  
dynamic link libraries. After awhile, your computer has lots of dlls and you  
can start experimenting by removing them from your computer and  checking if  
your machine still boots afterwards. Dotnet framework relies on and supports  
component development. Dotnet does not solve the fundamental problem of having
different versions of the same dll  to support different applications. However,  
the creation and version control appears to be easier in .Net. Let's write a  
simple dll console application in C and C# and compare the two. This  
application contains a client and a server. The client needs to add 3 and 5  
and she calls the server to do this for her. Let's start with C code. To  
implement this, we need five files:

//server.h
#define EXPORT extern "C" __declspec(dllexport)
EXPORT int CALLBACK mSum(int x,int y);
//server.c
#include
#include
#include "server.h"
EXPORT int CALLBACK mSum(int x, int y)
{
return x+y;
}
//server.mak
CC=cl
CFLAGS=-c  -G5  -W3  -Tp
LINKER=link
GUIFLAGS=-SUBSYSTEM:windows
DLLFLAGS=-SUBSYSTEM:console -DLL
GUILIBS=-DEFAULTLIB:user32.lib gdi32.lib winmm.lib comdlg32.lib comctl32.lib

server.dll:server.obj
$(LINKER) $(DLLFLAGS) -OUT:server.dll server.obj $(GUILIBS)
server.obj: server.c server.h
$(CC) $(CFLAGS) server.c
//client.mak
CC=cl
CFLAGS=-c -G5  -W3  -Tp
LINKER=link
GUIFLAGS=-SUBSYSTEM:console
DLLFLAGS=-SUBSYSTEM:console -DLL
GUILIBS=-DEFAULTLIB:user32.lib gdi32.lib winmm.lib comdlg32.lib comctl32.lib

client.dll:client.obj
$(LINKER) $(GUIFLAGS) -OUT:client.exe client.obj server.lib $(GUILIBS)
client.obj: client.c server.h
$(CC) $(CFLAGS) client.c
//client.c
#include
#include
#include "server.h"
void main()
{
printf("%d\n",mSum(5,3));
}

To compile these files, type nmake server.mak. If the compiler does not  
complaint type nmake client.mak and, if everything is OK, run client.exe.  
The total amount of code in the preceding examples is 36 lines (I have  
counted linker and compiler variables only once.).

Now, let's do the same thing in C#.


//client.cs
using System;
class Client
{
    public static void Main()
    {
        Console.WriteLine(Sum.mSum(3,5));
    }
}
//server.cs
public class Sum{
public static int mSum(int x,int y)
    {
        return x+y;
    }
}
    To compile and run this code, type csc /t:library /out:server.dll  
server.cs. This creates server.dll file. To compile the client, you need to
reference the server with csc /r:server.dl client.cs. The total amount of  
code is 15 lines, the code much simpler, and there are only 2 files to deal  
with. For a sufficiently large application the amount of C code is going to  
be comparable to the amount of C# code. The main advantage of C# comes from  
the reduced number of files and the absence of complex linker options and
header files.

Exercises:
1. Measure the time it takes to create a C# and C++ dll's for a specific  
application. Is C# component development always easier? How does debugging  
time compare?

2. Do you think server.dll can be used on a computer that does not have  
Common Language Runtime installed?

3. Find a mistake in this page.

4. Write a really cool program and send it to me. Do not forget to put a lot
of comments.

--

※ 修改:·walts 於 Jul 26 10:21:58 修改本文·[FROM: 166.111.142.118]
※ 来源:·BBS 水木清华站 smth.org·[FROM: 166.111.176.234]
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