Local data files in Visual C# Express 2008

While learning data binding for Windows.Forms, I noticed that changes made to data in the DataGridView weren't written back into the local SQL Server database file when the form was closing, even after calling TableAdapter.Update(). Turns out that Visual C# Express 2008 (and VS 2008 in general) copies your local data file each time you build your project to the output folder. The original version of the database file is only modified if you change the schema or edit data using VS. This also means that if you make changes to the data while programming, then change the database schema in VS, the changes you have made in the database file in the output folder would be overwritten.

See Also

• Local Data Overview
• How to: Manage Local Data Files in Your Project

Microsoft Word MailMerge Run-time error '5922'

When a MS-Access 2003 VBA script tried to open MS-Word and run the mail merge function, VBA displayed this error message:

Run-time error '5922':
Word was unable to open the data source

The problem was tracked to this statement:

    Dim objWordApp As Object
    Set objWordApp = CreateObject("Word.Application")
    With objWordApp
      ...
      .ActiveDocument.MailMerge.OpenDataSource Name:=CurrentDb.Name, SQLStatement:=sQuery, SubType:=wdMergeSubTypeWord2000

There's plenty of different solutions to this problem on the web. In this case, the problem was due to the second argument, the SQL query, sQuery, which had an error.

I spent some time browsing the web to investigate the run-time error, when it would have been more effective to first check the arguments in the subroutine call. Live and learn.

Visual Studio 2008 Express Data Source Limitations

Visual Studio Express 2008 for C# or VB only allows you to choose a limited number of data sources in the IDE. Open the Choose Data Source dialog using menu item Tools / Connect to Database, and in the Data Source list, there are only three items:

• Microsoft Access Database File
• Microsoft SQL Server Compact 3.5
• Microsoft SQL Server Database File

According to VS 2005 express: ".NET Framework Data Provider for ODBC" does not show up in Choose/Change Data Source dialog :(:

The data designers in the Express editions of Visual Studio only allow you to connect to SQL Server Express and Access (Jet) databases. I've passed your feedback along to the people who own these components in the hopes of getting this limitation clearly documented. As Ralph noted, you can still use the various .NET Data Providers at run-time. David Sceppa
ADO.NET Program Manager
Microsoft

I checked VisualStudio2008-ProductComparison-v1.08.pdf from Visual Studio 2008 Product Comparison Guide and there's no specific mention of this limitation for VS 2008 Express editions, other than Data Sources window displays the data sources in your project for creating data-bound controls.

Of course, I can work around this limitation programmatically but the learning value of VS Express editions falls when I can't match text and images from tutorials with what I see on screen.

Visual Basic short-circuit evaluation of expressions

Visual Basic seems to be the only language that evaluates all the operands of AND and OR operators instead of implementing short-circuit evaluation. In all other programming languages, such as C# or Java, expressions are evaluated from left to right, and the evaluation of expressions in statements exp1 AND exp2 and exp3 OR exp4 stop when exp1 = false or exp3 = true, respectively. This difference does surprise you if you come to VB from another programming language and you first write a conditional statement that relies on short-circuit evaluation, like this: If s IsNot Nothing And s.Length > 0 Then …

Two new keywords, AndAlso and OrElse were introduced in VB.Net to provide similar semantics to other languages supported by .Net. Working in more than one programming language at a time, I would have preferred some sort of backward compatibility compiler Option rather than adding new keywords to a language that already has too many.