Using Blobs with WTL OLE DB Database Applications

// Categories.H : Declaration of the CCategories class

#ifndef __CATEGORIES_H_
#define __CATEGORIES_H_

#ifndef __BLOBDDX_H__
	#error pubinfo.h requires blobddx.h to be included first
#endif

class CCategoriesAccessor
{
public:
	LONG m_CategoryID;	// Number automatically assigned to a new category.
	TCHAR m_CategoryName[16];	// Name of food category.
	TCHAR m_Description[1024];	// Name of food category.
	ISequentialStream* m_Picture;	// A picture representing the food category.

	// for BLOB_ENTRY_LENGTH_STATUS macro
	ULONG m_PictureLength;
	ULONG m_PictureStatus;

BEGIN_COLUMN_MAP(CCategoriesAccessor)
	COLUMN_ENTRY(1, m_CategoryID)
	COLUMN_ENTRY(2, m_CategoryName)
	COLUMN_ENTRY(3, m_Description)
	BLOB_ENTRY_LENGTH_STATUS(4, IID_ISequentialStream, STGM_READ, m_Picture, m_PictureLength, m_PictureStatus)
END_COLUMN_MAP()

DEFINE_COMMAND(CCategoriesAccessor, _T(" \
	SELECT \
		CategoryID, \
		CategoryName, \
		Description, \
		Picture  \
		FROM Categories"))

	// You may wish to call this function if you are inserting a record and wish to
	// initialize all the fields, if you are not going to explicitly set all of them.
	void ClearRecord()
	{
		memset(this, 0, sizeof(*this));
	}
};

class CCategories : public CCommand<CAccessor<CCategoriesAccessor> >
{
public:
	HWND m_hWndParent; // for file open dialog

	HRESULT Open()
	{
		HRESULT		hr;

		hr = OpenDataSource();
		if (FAILED(hr))
			return hr;

		return OpenRowset();
	}
	HRESULT OpenDataSource()
	{
		HRESULT		hr;
		CDataSource db;
		CDBPropSet	dbinit(DBPROPSET_DBINIT);

		dbinit.AddProperty(DBPROP_AUTH_CACHE_AUTHINFO, true);
		dbinit.AddProperty(DBPROP_AUTH_ENCRYPT_PASSWORD, false);
		dbinit.AddProperty(DBPROP_AUTH_MASK_PASSWORD, false);
		dbinit.AddProperty(DBPROP_AUTH_PASSWORD, OLESTR(""));
		dbinit.AddProperty(DBPROP_AUTH_USERID, OLESTR("Admin"));

		// file open dialog
		LPOLESTR osFileName = NULL;
		LPCTSTR lpcstrFileFilters = _T("Access databases (*.mdb)\0*.mdb\0All Files (*.*)\0*.*\0");
		CFileDialog dlg(TRUE, _T("mdb"), _T("Northwind.mdb"), OFN_HIDEREADONLY | OFN_OVERWRITEPROMPT, lpcstrFileFilters, m_hWndParent);
		if (dlg.DoModal() == IDOK) osFileName = CComBSTR(dlg.m_szFileName);
		dbinit.AddProperty(DBPROP_INIT_DATASOURCE, osFileName);

		dbinit.AddProperty(DBPROP_INIT_MODE, (long)16);
		dbinit.AddProperty(DBPROP_INIT_PROMPT, (short)4);
		dbinit.AddProperty(DBPROP_INIT_PROVIDERSTRING, OLESTR(""));
		dbinit.AddProperty(DBPROP_INIT_LCID, (long)1033);
		hr = db.Open(_T("Microsoft.Jet.OLEDB.4.0"), &dbinit);
		if (FAILED(hr))
			return hr;

		return m_session.Open(db);
	}
	HRESULT OpenRowset()
	{
		// Set properties for open
		CDBPropSet	propset(DBPROPSET_ROWSET);
		propset.AddProperty(DBPROP_IRowsetChange, true);
		propset.AddProperty(DBPROP_UPDATABILITY, DBPROPVAL_UP_CHANGE | DBPROPVAL_UP_INSERT | DBPROPVAL_UP_DELETE);

		return CCommand<CAccessor<CCategoriesAccessor> >::Open(m_session, NULL, &propset);
	}
	CSession	m_session;
};

#endif // __CATEGORIES_H_