Файловый архив студентов. Файловый архив студентов.
1331 вуз, 5513 предмет.
/ Регистрация
FAQ Обратная связь Вопросы и предложения
Добавил:
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Таврический Национальный Университет им. В.И. Вернадского
Предмет:
Программирование
Файл:

Microsoft Visual C++ .NET Professional Projects - Premier Press

.pdf
Скачиваний:
180
Добавлен:
24.05.2014
Размер:
26 Мб
Скачать
☆

960

 

Part XII

APPENDIXES

 

 

 

 

 

In the following sections, I will discuss these categories of classes.

Form

All the windows within an application are represented by using the Form class.

These windows within an application are called forms. Some examples of forms

are dialog boxes, modeless windows, and the parent and child windows of Win-

dows-based applications.

 

 

Y

 

 

 

L

Controls

 

F

 

 

M

 

You can create interfaces with rich functionality by using the control classes in the

 

A

 

 

System.Windows.Forms namespace. These classes derive from the Control class.

These control classes can be further classified as follows:

 

E

 

 

Data entry classes. For example, the TextBox control.

 

T

 

 

 

Data display classes. For example, the Label control.

Command-invoking classes. For example, the Button control.

Components

Classes belonging to the components category provide you with the necessary tools to enhance the user interface of a Windows-based application. For example, the ToolTip class allows you to provide tool tips for user interface components, such as a menu option. The menu classes, Menu, MenuItem, and ContextMenu, are also part of this class. You learned how to handle the Menu and MenuItem classes in Chapters 10 to 14.

NOTE

The components classes are not derived from the Control class.

Common Dialog Boxes

Classes in the common dialog boxes category provide you with the functionality of the common dialog boxes, which include Open, Save, Print, and other such

Team-Fly®

NAMESPACES AND ATTRIBUTES Appendix C 961

commonly available dialog boxes. For example, the OpenFileDialog class provides the functionality of the Open dialog box.

To summarize, the System namespace comprises the main namespace in the

.NET Framework that simplifies the creation of applications by using Visual Studio.NET.

Attributes

As specified in Chapter 18, there are five predefined categories of attributes available for you to work with:

COM attributes

IDL attributes

ATL Server attributes

OLEDB consumer attributes

Compiler attributes.

The following sections describe some of the attributes belonging to each of these categories.

COM Attributes

As you have experienced by now, COM attributes reduce your coding effort to a great extent. Some of the COM attributes are the following:

coclass. Creates a COM component.

aggregatable. Specifies that a component can be aggregated by others.

aggregates. Specifies that the component aggregates the target class.

progid. Defines the ProgID for a component.

com_inteface_entry. Creates an entry in the COM map for an interface.

perf_counter. Adds performance counter support to a specific class member.

soap_handler. Provides methods for processing SOAP messages.

synchronize. Synchronizes simultaneous access to a component’s method.

threading. Specifies the threading model for a component.

962

 

Part XII

APPENDIXES

 

 

 

 

 

IDL Attributes

To maintain an IDL file, earlier you had to have the knowledge about the structure of the IDL file and had to rely on the wizard that allowed you to selectively modify the file. Now with IDL attributes, you have the facility to modify the IDL file from within its source code. IDL attributes can be used either in combination with the COM attributes or as standalone attributes. With COM, the IDL attributes inject code into the project. While used alone, these allow you to define interfaces and the IDL file. Some of the IDL attributes are listed here:

id. Specifies a DISPID for a function.

dispinterface. Places an interface as a dispatch interface in the IDL file.

dual. Places an interface as a dual interface in the IDL file.

include. Specifies the header files to be included in the IDL file.

import. Specifies the IDL or H files that you want to refer to from the main IDL file.

in. Specifies that the parameter is to be passed to the called procedure.

coclass. Places a class as a coclass in the IDL file.

out. Identifies the parameters received from the server.

progid. Specifies the ProgID of an object.

ATL Server Attributes

The ATL Server template provides an option to use the ATL Server attributes while creating an ATL Server. Some of the attributes under this category are the following:

soap_handler. Provides the methods required to handle SOAP-related messages.

soap_method. Exposes the specified method as a SOAP method and generates the WSDL description.

soap_header. Assigns a member to hold the header information in a SOAP message.

request_handler. Exposes a class as an ATL Server request handler.

NAMESPACES AND ATTRIBUTES Appendix C 963

OLE DB Consumer Attributes

The OLEDB attributes inject code to create an OLEDB consumer with the functionality of the commonly performed operations that include opening a table, executing commands, and retrieving data. Some of the attributes under this category are the following:

db_table. Opens a table.

db_source. Creates a connection.

db_param. Associates a variable with an input or output parameter.

db_command. Executes an OLEDB command.

db_column. Binds a column to a rowset.

Compiler Attributes

Some of the compiler attributes are the following:

event_receiver. Creates an event receiver.

event_source. Creates an event source.

version. Identifies a particular version of a class or an interface.

This page intentionally left blank

Appendix D

Migrating Unmanaged Code to Managed Code

Managed code enables you to utilize the significant features of the .NET Framework, such as the CLR, garbage collection, and JIT compilation. In the chapters, you learned to create fresh Managed C++ applications. But, can you

only create a managed application from scratch? If not, then what happens to the existing unmanaged applications? Imagine re-creating those enormous applications. Obviously, you wouldn’t choose to do a complete migration. Instead, you would want to implement selected functionality using Managed C++. To meet this end, Visual C++ .NET allows you to write an application that can be a mix of managed and unmanaged code. This appendix shows you how to migrate an unmanaged application to a managed application.

Sample Application

To illustrate the Visual C++ .NET feature just mentioned, I will be using a Win32 application. Following is the code of the Win32 application. Comment entries provide the required explanations.

//This is a simple application that contains a class with two member functions, GetStr and SetStr, a constructor, and a member variable defined in it. The functionality that this class exposes includes accepting a string, storing it in the class, retrieving the stored value, and displaying the value.

#include <iostream> using std::cout; using std::endl;

//unmanaged C++ class definition

class CDisplayString

{

public:

CDisplayString(char *);

char * GetStr(void);

void SetStr(char *);

private:

char * m_str;

MIGRATING UNMANAGED CODE TO MANAGED CODE Appendix D 967

};

// the constructor

CDisplayString::CDisplayString(char * str)

{

m_str = str;

}

// Get function

char * CDisplayString::GetStr(void)

{

return m_str;

}

//set function

void CDisplayString::SetStr(char * str)

{

m_str = str;

}

// main entry point function int main(void)

{

CDisplayString aString(“This is the string set by the constructor”);

char * pStr = aString.GetStr();

// display it on the command line cout << pStr << endl;

// change the value

aString.SetStr(“... and this is the changed value.”); pStr = aString.GetStr();

// display the changed value on the command line cout << pStr << endl;

}

968

 

Part XII

APPENDIXES

 

 

 

 

 

To see how this application works, all you have to do is compile it using the following command:

cl win32code.cpp

I will now explain the changes that you have to do in this application to make it a mixed application. The following are the steps to follow:

1. Include the managed H files:

#include “vcclr.h”

2. Add the DLLs and namespaces required for managed code:

#using <mscorlib.dll>

#using namespace System;

#using namespace System::Runtime::InteropServices;

3.At this stage, if you compile the code, the compiler throws an error stating that the /clr option is required. To avoid these messages, you need to compile the application using the /clr option. Try it and see that it gets compiled now.

Let me now add some more Managed C++ features. Perform the following steps to introduce those changes:

1.Open the file and edit the code to reflect the following changes.

2.Replace the line

char * m_str;

with

gcroot<String*> m_str;

//use of the gcroot template allows us to embed

//a __gc pointer in an unmanaged class

3.Edit the constructor to replace the line:

m_str = str;

with

m_str = new String(str);

// to allocate a managed string

MIGRATING UNMANAGED CODE TO MANAGED CODE Appendix D 969

4. Replace the line:

return m_Str;

with

char * pStr = 0;

//Exception handling try

{

//copies the contents of m_str into the Windows global heap,

//converting to ANSI format on-the-fly. It allocates

//the required native heap memory

pStr = static_cast<char*>(Marshal::StringToHGlobalAnsi(m_str).ToPointer());

}

// m_str is null

catch (ArgumentException* e)

{

Console::WriteLine(e->ToString());

}

// could not allocate enough memory on native heap catch (OutOfMemoryException* e)

{

Console::WriteLine(e->ToString());

}

5. Edit the setstr function. Comment the existing line:

m_str = str;

Add the following line:

m_str = new String(str);

6.Add the following code to the main function to clean the memory:

//deallocate memory from Windows global heap for the string Marshal::FreeHGlobal(pStr);

pStr = 0;

Соседние файлы в предмете Программирование
Помощь Обратная связь Вопросы и предложения Пользовательское соглашение Политика конфиденциальности