Article ID: 161307
Article Last Modified on 7/13/2004
APPLIES TO
- Microsoft Visual Basic 6.0 Learning Edition
- Microsoft Visual Basic 6.0 Professional Edition
- Microsoft Visual Basic 6.0 Enterprise Edition
- Microsoft Visual Basic 4.0 Standard Edition
- Microsoft Visual Basic 4.0 Professional Edition
- Microsoft Visual Basic 4.0 32-Bit Enterprise Edition
This article was previously published under Q161307
SUMMARY
The structure of FoxPro tables has changed with the release of Visual FoxPro 3.0. Visual FoxPro 3.0 now has a database container file with the extension .DBC that contains references to tables, but does not contain the tables themselves. Like previous versions of FoxPro, the tables still reside in their own .DBF files.
The structure of a Visual FoxPro table depends upon whether that table is included in a database container. A table not included in a database container is called a "free table" and its structure differs from a "database table." Visual Basic must know which type of table it is trying to access in order to know how to read the structure of the table.
With Visual FoxPro "free tables," Visual Basic recognizes these files much like it recognizes older FoxPro tables. Visual Basic's database object corresponds to the directory in which the "free tables" reside. However, with "database tables," the Visual Basic database object corresponds to the Visual FoxPro .DBC file, which contains reference to the "database tables."
MORE INFORMATION
Free Tables
Here is some sample code to open the Foxuser.DBF table:
Private Sub Form_Load()
Dim FoxFreeDB As Database
Dim FoxFreeRS As Recordset
Set FoxFreeDB = Workspaces(0).OpenDatabase("C:\VFP", False, _
False, "FoxPro 3.0;")
Set FoxFreeRS = FoxFreeDB.OpenRecordset("Foxuser")
Set Data1.Recordset = FoxFreeRS
End Sub
Database Tables
Here is some sample code to open the Employee.DBF table that resides in the Tastrade.DBC database container:
Private Sub Form_Load()
Dim FoxDataDB As Database
Dim FoxDataRS As Recordset
Set FoxDataDB = Workspaces(0).OpenDatabase( _
"C:\VFP\Samples\Mainsamp\Data\Tastrade.DBC", _
False, False, "FoxPro DBC;")
Set FoxDataRS = FoxDataDB.OpenRecordset("Employee")
Set Data1.Recordset = FoxDataRS
End Sub
When Visual Basic accesses a Visual FoxPro "database table," it uses the .DBC file to list and locate .DBF files. Visual Basic does not use the .DBC file to determine the structure of the .DBF files; that information is obtained by examining the .DBF file itself. This means that long field names, which Visual FoxPro stores in the .DBC file, will not be accessible in Visual Basic. For example, the above sample that reads the Employee table will have an Employee ID field "Employee_I" instead of "Employee_ID" because the .DBF file does not store the long field name.
Another ramification of reading the linked tables directly is that Jet marks these tables as read-only because all the Referential Integrity rules for a table are stored in the database container file. Visual FoxPro free tables are also read only.
NOTE: The 16-bit edition of Visual Basic version 4.0 cannot read files in the Visual FoxPro version 3.0 format without a third-party ODBC driver.
REFERENCES
For more information explaining why the Visual Basic Data Control does not list all possible Visual FoxPro connect properties, please see the following article in the Microsoft Knowledge Base:
140770 : PRB: Accessing Visual FoxPro 3.0 Files from Visual Basic 4.0
Additional query words: fox foxpro dbc open dbf xbase kbVBp600 kbVBp400 kbdse kbDSupport kbVBp kbVFP300
Keywords: kbhowto KB161307
