readme.wzd

《Visual C++ MFC编程实例》配套代码,如果大家正在学习此教程

/////////////////////////////////////////////////////////////////////
// Modify Stdafx.h
/////////////////////////////////////////////////////////////////////

// 1) ensure to include database includes in Stdafx.h

#ifndef _AFX_NO_DB_SUPPORT
#include <afxdb.h>			// MFC ODBC database classes
#endif // _AFX_NO_DB_SUPPORT

#ifndef _AFX_NO_DAO_SUPPORT
#include <afxdao.h>			// MFC DAO database classes
#endif // _AFX_NO_DAO_SUPPORT

/////////////////////////////////////////////////////////////////////
// Modify Document Class
/////////////////////////////////////////////////////////////////////

// 1) embed database class in document class (or other class)
	CDocument m_WzdDocument;

// 2) open database in CDocument's OnNewFile or OnOpenFile
	if(!m_WzdDatabase.Open(
			NULL,								// Data source name, NULL if defined in DSN= below
			FALSE,								// exclusive access, NOT SUPPORTED, should always be false
			FALSE,								// read only access
			"ODBC;DSN=MS Access 97 Database")	// connect string DSN= is data source name,
												// UID= is user id, PSW= is password
			)
	{
		AfxMessageBox("Failed to open database.");
	}
	

// 3) close database in CDocument's DeleteContents()
	// close database
	m_WzdDatabase.Close();

/////////////////////////////////////////////////////////////////////
// Modify View Class
/////////////////////////////////////////////////////////////////////

// 1) create record set object
	CWzdRecordSet wzdSet(GetDocument()->GetDatabase());

// 2) open all records in table
	wzdSet.Open();

// 3) scroll through records
	while (! wzdSet.IsEOF())
	{
		// values can be accessed from record set member variables:
		//		wzdSet.m_CustomerID  
		//		wzdSet.m_CompanyName 
		//		wzdSet.m_ContactName 
		//			etc.

		wzdSet.MoveNext();
	}

// 4) if we can't update or append records, leave now
	if (!wzdSet.CanUpdate() || !wzdSet.CanAppend())
		return;

// 5) add a record
	try
	{
		// add new record
		wzdSet.AddNew();

		// initialize each field
		wzdSet.m_CustomerID="ABCDE";
		wzdSet.m_CompanyName="ABC Inc.";
		//etc.

		// update database
		wzdSet.Update();
	}
	catch (CDBException *e)
	{
		// AddNew failed
 		AfxMessageBox(e->m_strError);
		e->Delete();
	}

// 6) edit a record
	wzdSet.MoveFirst();
	try
	{
		wzdSet.Edit();

		// update affected fields
		wzdSet.m_CompanyName="ABCEF Inc.";
		wzdSet.m_ContactName="Frank";
		//etc.

		// update database
		wzdSet.Update();
	}
	catch (CDBException *e)
	{
		// Edit failed
 		AfxMessageBox(e->m_strError);
		e->Delete();
	}


// 7) delete a record
	try
	{
		// delete record to which we're currently opened
		wzdSet.Delete();
	}
	catch (CDBException *e)
	{
		// Delete failed
 		AfxMessageBox(e->m_strError);
		e->Delete();
	}

// 8) close record set
	wzdSet.Close();

///////////////////////////////////
// RECORD FILTERING   
///////////////////////////////////
// 9) open record set with a simple "WHERE" SQL filter
	wzdSet.m_strFilter = "[Country]='UK'";
	if(!wzdSet.Open() || wzdSet.IsEOF())
	{
		AfxMessageBox("Cannot find records.");
	}

	// scroll through records as above...
	while (! wzdSet.IsEOF())
	{
		wzdSet.MoveNext();
	}
	wzdSet.Close();


// 10) open a record set with a complete SQL SELECT statement
	wzdSet.m_strFilter = ""; // appended to the following!
	if (!wzdSet.Open(AFX_DB_USE_DEFAULT_TYPE,
	 	"SELECT [CustomerID], [CompanyName], [ContactName], \
[ContactTitle], [Address], [City], [Region], [PostalCode], [Country], [Phone], [Fax] \
FROM [Customers] WHERE [Country] = 'Mexico'") ||
			wzdSet.IsEOF())
	{
		AfxMessageBox("Cannot find records.");
	}

	// scroll through records as above...
	while (! wzdSet.IsEOF())
	{
		wzdSet.MoveNext();
	}
	wzdSet.Close();

////////////////////////////////////
// MULTIPLE TABLE TRANSACTIONS
////////////////////////////////////

// NOTE: when performing related operations on more then one database
// table at a time, an error in any one of these transactions should undo
// or "rollback" all of the changes made

// 11) Create a transaction we can rollback
	GetDocument()->GetDatabase()->BeginTrans();
	try
	{
		// perform transactions on several database tables/records
		wzdSet.Open();
		wzdSet.Update();
		// Success
		GetDocument()->GetDatabase()->CommitTrans();
	}
	catch (CDBException *e)
	{
		// An exception occurred, rollback the transaction
		GetDocument()->GetDatabase()->Rollback();
 		AfxMessageBox(e->m_strError);
		e->Delete();
	}
	// since this was allocated on stack, returning will also close record set
	wzdSet.Close(); 



/////////////////////////////////////////////////////////////////////
// From: Visual C++ MFC Programming by Example by John E. Swanke
// Copyright (C) 1998 jeswanke. All rights reserved.
/////////////////////////////////////////////////////////////////////