Enumerating Databases and Database Volumes
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8/28/2008
Enumerating databases is the process of sequentially accessing each database in a group. The group can include all databases in the object store, databases of a specified type, or databases in all of the mounted volumes. Use enumeration when you need to change all databases of a certain type or synchronize data between a desktop computer and a Windows Embedded CE–based device.
Use the CeFindFirstDatabaseEx (CEDB) and the CeFindNextDatabaseEx (CEDB) functions to enumerate databases in a specified database volume. The volume can be the object store or any mounted database volume. CeFindFirstDatabaseEx and CeFindNextDatabaseEx have an additional parameter that identifies the CEGUID of the volume. If you pass in an invalid CEGUID, Windows Embedded CE searches all mounted database volumes on a Windows Embedded CE–based device, including the object store. You can also enumerate mounted database volumes by calling the CeEnumDBVolumes (CEDB) function.
When you are finished, call the CloseHandle function to close the enumeration handle.
The following code example shows how to enumerate databases in the object store.
void EnumeratingDBs (void)
{
DWORD dwError; // Return value of the GetLastError function.
TCHAR szMsg[100]; // String that contains the error message and database data.
HANDLE hEnumDB; // Handle to a database enumerator.
CEOID CeOid; // Object identifier of a database.
CEOIDINFO CeObjectInfo; // Structure that contains database data.
PCEGUID pceguid = NULL; // Pointer to the mounted volume identifier. NULL means all mounted database volumes are to be searched.
// Find the first database. Set the database type to 0, so all types of databases are enumerated. If pceguid is set to NULL or an invalid GUID is created by CREATE_INVALIDGUID, all mounted database volumes are searched.
hEnumDB = CeFindFirstDatabaseEx (pceguid, 0);
if (hEnumDB == INVALID_HANDLE_VALUE)
{
if (GetLastError () == ERROR_OUTOFMEMORY)
wsprintf (szMsg, TEXT("Out of memory."));
else
wsprintf (szMsg, TEXT("Unknown error."));
return;
}
while ((CeOid = CeFindNextDatabaseEx (hEnumDB, pceguid)) != 0)
{
// Retrieve database data.
if (!CeOidGetInfoEx (pceguid, CeOid, &CeObjectInfo))
{
// Your error-handling code goes here.
CloseHandle (hEnumDB); // Close the search handle.
return;
}
else
{
wsprintf (szMsg, TEXT("The name of the database is: %s"), CeObjectInfo.infDatabase.szDbaseName);
}
}
// Error handling if CeFindNextDatabaseEx fails.
dwError = GetLastError ();
if (dwError == ERROR_KEY_DELETED)
{
// A database has been deleted during enumeration. You must restart the enumeration process.
wsprintf (szMsg, TEXT("A database was deleted during enumeration."));
}
else if (dwError == ERROR_NO_MORE_ITEMS)
{
wsprintf (szMsg, TEXT("No more item to enumerates."));
}
else
{
wsprintf (szMsg, TEXT("Unknown error."));
}
// Close the search handle.
CloseHandle (hEnumDB);
}